Answer:
Explanation:
During meiosis, each chromosome has 2 chromatids. When homologous chromosomes pair they form a tetrad (2 chromosomes, 4 chromatids).
Crossing over can happen between 2 out of the 4 chromatids, and as a result, only half of the resulting gametes (at most) can be recombinant. The other 2 gametes will be parental.
Which of the following sequences correctly represents the flow of electrons during photosynthesis?
a. NADPH -> O2 -> CO2
b. H2O ->S NADPH -> Calvin cycle
c. H2O -> photosystem I -> photosystem II
d. NADPH -> electron transport chain -> O2
Answer: b. H2O ->S NADPH -> Calvin cycle
Explanation:
Photosynthesis can be compartmentalized into two phases: one that depends directly on the light - photochemical phase and one that does not depend on the light, called chemical phase.
The first uses H2O to produce ATP and a reduced electron carrier (NADPH + H +), the second uses ATP, NADPH + H + and CO2 to produce sugar. In the photochemical phase, light energy is used to produce ATP from ADP + Pi, through a set of reactions mediated by groups of molecules - the photosystems - in a cycle called photophosphorylation.
There are two types of photophosphorylation: one non-cyclic that produces NADPH and ATP and one cyclic that produces only ATP. In the chemical phase, which is not directly dependent on light, non-cyclic photophosphorylation products - NADPH and ATP - and CO2 are used to produce glucose, in the so-called Calvin-Benson cycle. Although it is also called the dark phase, it is not independent of light, since for the enzyme responsible for fixing CO2, RuBisCo, requires light to be reduced and to be in its active state.
Extensive irrigation in arid regions causes salts to accumulate in the soil. (When water evaporates, salts that were dissolved in the water are left behind in the soil.) Based on what you learned about water balance in plant cells, explain why increased soil salinity (saltiness) might be harmful to crops.
Answer:
Increased salinity will result in total crop failure in a field. This is because plants need to take up water from the soil for growth and development. However the salinity levels of this soil will, rather, draw water from the plants by osmosis. This is because the soil water will be hypertonic to the plant's cells cytoplasm and even seeds. In osmosis, water moves from the hypotonic solution to the hypertonic solution through a semi-permeable membrane until osmotic equilibrium is achieved. Planted seeds with therefore hardly germinate and plants will wilt and die, as a result.
Answer:
Increased salinity will result in total crop failure in a field. This is because plants need to take up water from the soil for growth and development. However the salinity levels of this soil will, rather, draw water from the plants by osmosis. This is because the soil water will be hypertonic to the plant's cells cytoplasm and even seeds. In osmosis, water moves from the hypotonic solution to the hypertonic solution through a semi-permeable membrane until osmotic equilibrium is achieved. Planted seeds with therefore hardly germinate and plants will wilt and die, as a result.
Explanation:
Contrast meiosis with mitosis, mentioning homologous chromosomes, chromatids, tetrads and crossing over.
Answer:
Explanation:
Mitosis takes place in somatic cells of the body while the meiosis takes place in the germ cells. The mitosis is the equational division while the meiosis is reductional division.
The meiosis has 2 cell divisions i.e. meiosis I and meiosis II. The mitosis is a single division.
The pairing between the homologous chromosome/synapsis occurs in meiosis. It is not found in mitosis.
During the pachytene stage of meiosis, crossing over takes place. The homologous chromosome exchanges its genetic materials in crossing over.
In mitotic cell division, the chromatids do not exchange their genetic material.
The chromosome numbers are always the same as the parent cell in the mitotic division. In meiosis, the number of the chromosome turns to half of their parent cells.
There are 4 haploid chromosomes/tetrads forms at the end of meiosis. In meiotic division 2 chromosomes form from the parent cells.
Final answer:
Meiosis includes two nuclear divisions leading to four haploid genetically distinct cells, with homologous chromosomes pairing, crossing-over, and lining up as tetrads. Mitosis results in two identical diploid cells without these features. A diploid human cell has 46 chromosomes, whereas a haploid cell has 23.
Explanation:
In comparing meiosis and mitosis, several key differences are noteworthy. Both processes are preceded by one round of DNA replication, but meiosis involves two nuclear divisions that result in four genetically distinct haploid daughter cells, whereas mitosis results in two identical diploid daughter cells.
During meiosis I, a crucial aspect is the pairing of homologous chromosomes, each consisting of two sister chromatids. They become bound together with the synaptonemal complex, leading to the formation of chiasmata during crossing-over. Crossing-over is the exchange of genetic material between non-sister chromatids of homologous chromosomes, bringing about new combinations of genes. After this genetic recombination, homologous chromosomes line up along the metaphase plate in groups of four, known as tetrads, with kinetochore fibers from opposite poles attached to each homolog's kinetochore.
A diploid human cell, such as a skin or liver cell, has 46 chromosomes. In contrast, a haploid human cell, like a sperm or egg cell, has 23 chromosomes. Genetic variation arises from crossing-over, the independent assortment of chromosomes during meiosis, and random fertilization of gametes.
name Streptococcus agalactiae, what morphology would you expect these cells to have?
Answer:
round and in chains
Explanation:
Streptococcus agalactiae is a gram positive bacteria. It is facultative anaerobe and forms a part of microbiota in gastro intestinal and urinary tract of healthy humans. It can cause infections in immuno compromised beings.Its genus name describes its morphology. Coccus are round spherical shaped bacteria. Strepto means that the bacteria are present in chain form. Hence this bacteria is spherical and arranged in chains.
There are several other types of bacterial morphology. For example: Staphylococcus means that the bacteria is again spherical but this time arranged in groups. Diplococcus means that the spherical bacteria is arranged in a pair. Similarly, bacillus is used to describe a rod shaped bacteria.
What functions do membrane proteins serve? synthesize phospholipids for the maintenance and growth of the cell membrane transport nutrients into the cell that cannot otherwise cross the phospholipid bilayer transport wastes out of the cell that cannot otherwise cross the cell membrane prevent small, uncharged substances from crossing the phospholipid bilayer synthesize DNA within the cell using raw materials found outside the cell
Answer:
transport nutrients into the cell that cannot otherwise cross the phospholipid bilayer transport wastes out of the cell that cannot otherwise cross the cell membraneExplanation:
Cell membrane integral proteins especially trans-membrane proteins facilitate and regulate the movement of particular molecules across the cell membrane. Examples of these molecules are glucose and sodium ions. These molecules are either charged and cannot pass through the hydrophobic lipid layer of the cell membrane and/or are too large to pass through the cell membrane pores (like the aquaporins).Other types of cell membrane proteins are peripheral proteins. Collectively these proteins can have several other functions include cell signaling, enzymatic activity, cell-to-cell recognition , and etcetera.
Membrane proteins serve various functions including the transport of nutrients into and out of the cell, excretion of wastes, signal transduction, and serving as anchors for structural components. Integral proteins form channels or pumps for transport, while peripheral proteins function as enzymes or recognition sites. Together, they are essential for maintaining cellular homeostasis.
Explanation:Functions of Membrane ProteinsMembrane proteins are crucial for a variety of cellular processes. Firstly, they are involved in the transport of nutrients across the cell membrane. Such nutrients cannot cross the phospholipid bilayer on their own due to their polar nature or size. Similarly, membrane proteins assist in the excretion of waste products like CO₂, which need to be regulated within the cell. Another key role of these proteins is in transmitting signals; acting as signal transducers, they allow the cell to respond to external cues. Additionally, they also serve as anchors for the cell's structural framework, interacting with the cellular cytoskeleton and extracellular matrix.
Specifically, these proteins can be classified into two major classes: integral proteins, which are typically embedded within the lipid bilayer, and peripheral proteins, which are associated with the bilayer's surface. Integral proteins can form channels or pumps that facilitate active and passive transport, while peripheral proteins can function as enzymes or cell recognition sites that aid in immune responses or cell adhesion.
Overall, membrane proteins are indispensable for maintaining the cell's internal environment, allowing for a controlled exchange of substances to sustain cellular life.
What are the genotypic differences between F-, F+ and Hfr cells?
Answer:
The fertility factor or the F factor signifies a plasmid in some bacteria, which allows the conduction of genetic substance from a donor cell to the recipient by the process of conjugation, leading to recombination.
The genotypic difference between the F- cells, F+ cells, and the Hfr cells are that the F- cells are devoid of the F factor, the F+ cells possess autonomous F factor, that is, a segment of DNA, which can replicate autonomously in the cell. In case of Hfr, the F factor is integrated into its chromosomal DNA, thus, they carry an integrated F factor.
In sheep, white vs yellow body fat is determined by a single pair of autosomal alleles. In a large, randomly mating flock, 23 percent of the sheep have white fat and 77 percent have yellow fat. You may conclude from this data that:
a. The allele for yellow is dominant to white
b. The allele for white is dominant to yellow
c. The alleles for yellow and white are codominant
d. The alleles for white and yellow are in a Hardy-Weinberg equilibrium
e. None of the above are valid conclusions
Answer:
Option A , The allele for yellow is dominant to white
Explanation:
It is given that 23 percent of the sheep have white fat and 77 percent have yellow fat.
Thus, it is clear that sheeps with yellow fat is a dominant characteristics.
Usually, the frequency of homozygous recessive allele in a given population is represented by [tex]q^2[/tex]
and here [tex]q^2 = 0.23[/tex]
Frequency of allele for white fat [tex]= q = \sqrt{0.23} \\q= 0.479[/tex]
While frequency of homozygous dominant allele and heterozygous dominant allele is represented by [tex]p^2+2pq\\[/tex]
And here [tex]p^2+2pq = 0.77[/tex]
Allele for yellow fat [tex]= 1-q\\= 1-0.479\\= 0.521[/tex]
Hence, option A is correct.
A sex linked trait can be defined by which genotypes. Choose all which apply.
a. Coded for on the X and Y chromosomes
b. Coded for on the X but not Y chromosome
c. Coded for on the Y but not X chromosom
d. a dominant allele on any chromosome
Answer:
a. Coded for on the X and Y chromosomes
b. Coded for on the X but not Y chromosome
c. Coded for on the Y but not X chromosome
Explanation:
The X and Y chromosomes are the sex chromosomes as they are involved in sex determination. All the genes that are present on the X and Y chromosomes are inherited along with these chromosomes and therefore, exhibit sex-linked inheritance.
X and Y chromosomes share a homologous region. Therefore, the sex-linked genes are defined as the ones present on both X and Y chromosomes as well as the ones that are present on either X or Y chromosomes.
For example, the gene for hemophilia is present on the X chromosome; but not on the Y chromosome. The SRY gene is present only on the Y chromosome.
Write down the possible genotypes, as determined by the phenotype.
a. If the phenotype is that of the dominant trait (for example, purple flowers), then the genotype is either homozygous dominant or heterozygous (PP or Pp in this example).
b. If the phenotype is that of the recessive trait, the genotype must be homozygous recessive (for example, pp).
c. If the problem says "true-breeding," the genotype is homozygous.
a. If the phenotype is that of the dominant trait (for example, purple flowers), then the genotype is either homozygous dominant or heterozygous (PP or Pp in this example).
To draw the genotype here, you have two possible options: PP homozygous dominant or Pp heterozygous dominant.
b. If the phenotype is that of the recessive trait, the genotype must be homozygous recessive (for example, pp).
Yes, in this case, if you want a recessive trait to show on the phenotype your only option is to have pp alleles.
c. If the problem says "true-breeding," the genotype is homozygous.
In this case, your only option is P or p.
Either if it's dominant ( capital letter) or recessive (lower letter)
In the history of Earth and the evolution of cells, aerobic cells appeared first and anaerobic cells appeared later.
a. True
b. False
Answer:
False
Explanation:
Scientist believe that the primitive atmosphere lacked free oxygen. Oxygen is a highly reactive molecule that would have made difficult for complex macromolecules to appear and then create life. Rocks from the precambrian period support this theory.
Anaerobic cells appeared first, then photosynthesis appeared filling the atmosphere with oxygen and the aerobic organism develop cellular respiration to obtain energy, a process more efficient than anaerobic respiration.
Which of the following organisms arose during the Mesozoic Era? a. mammals c. insects b. birds d. salamanders
The Mesozoic era is featured by the arousal of b. birds.
Explanation:The Mesozoic Time is the age of the dinosaurs and kept going nearly 180 million a long time from around 250 to 65 million a long time back. It includes periods called the Triassic, Cretaceous, and Jurassic periods. A mass-extinction stamped the starting and conclusion of the Mesozoic Period. The occasion that caused the move from the Paleozoic time to the Mesozoic period was the most prominent termination this soil has seen.
There's noteworthy prove that birds developed inside theropod dinosaurs, particularly, that winged creatures are individuals of Maniraptora, a category which belongs to dinosaurs period.
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In cellular respiration, the steps following glycolysis depend on whether oxygen is present. Select the BEST explanation:
A
If oxygen is present, production of acetyl-CoA, the citric acid cycle, and electron transport chain follow in order. If no oxygen is present, photosynthesis occurs starting with Photosystem II.
B
If oxygen is present, production of acetyl-CoA, the citric acid cycle, and electron transport chain follow in order. If no oxygen is present, either lactic acid fermentation or alcoholic fermentation follows.
C
In the presence of oxygen, carbon fixation occurs during the Calvin cycle, when a carbon atom from atmospheric carbon dioxide is added to a 5-carbon sugar.
D
Regardless if oxygen is present or not, the production of acetyl-CoA, the citric acid cycle, and electron transport chain follow in order.
SECOND QUESTION is the picture
here are the answer choices if you can only see the picture.
A. destroyed.
B. absorbed.
C. reflected.
D. converted to heat.
Answer:
For the first question the answer is B. For the second question the answer is C.
Explanation:
The first question: If oxygen is present, production of acetyl-CoA, the citric acid cycle, and electron transport chain follow in order. If no oxygen is present, either lactic acid fermentation or alcoholic fermentation follows.
The second question: Leaves appear green because the green portion of visible light that strikes them is reflected.
Hope this helps
-Amelia
Cellular respiration is a type of respiration ( metabolic pathway )that involves the breaking down of glucose into ATP. and it follows four ( 4 ) stages which are ;
glycolysis, pyruvate oxidation, Krebs cycle, oxidative phosphorylation.Glycolysis is the stage ( metabolic pathway) in cellular respiration when glucose is converted into two molecules of pyruvate in the presence of oxygen or the conversion of glucose into two molecules of lactate if no oxygen is present during the process
Hence we can conclude that The best explanation on the steps following glycolysis is If oxygen is present, production of acetyl-CoA, the citric acid cycle and electron transport chain follow in order. if no oxygen is present either lactic acid fermentation or alcoholic fermentation follows.
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The net primary productivity is usually more than 80% of gross primary productivity.
a. True
b. False
Answer:
b. False
Explanation:
As GPP stands for the gross primary productivity, it's the total amount of energy produced in the process and the NPP is the net primary productivity. NPP is the difference between the GPP and the energy used by the producer for the process of respiration. GPP is a continuous and ongoing process that consumes the energy as compared to the NPP that store energy and not being used. Thus, GPP can affect NPP but NPP does not affect GPP. For example, GPP is completely being dependent on the chlorophyll content of the plant, but NPP is independent of that content of chlorophyll.What are the components of the CNS? What is the function of each?
Answer:
Two main component of Central nervous system are brain and spinal cord.
Brain:
Brain acts as the main coordinating center of the body. The brain is protected in the skull. The brains control the emotions, thought process and learning memory of the organism. The brain interprets the information received by the five different sense organs.
Spinal cord:
The spinal cord is involved in the reflex action of the body. Spinal cord is involved in the somatosensory organization of the body. The motor pathways are originated from the spinal cord. Body's proprioceptive information travels through the spinal cord.
The decline of MPF activity at the end of mitosis is due to
a. the destruction of the protein kinase Cdk.
b. decreased synthesis of Cdk.
c. the degradation of cyclin.
d. the accumulation of cyclin.
Answer:
c. the degradation of cyclin is the correct answer.
Explanation:
The decline of MPF activity at the end of mitosis is due to the degradation of cyclin.
The MPF stands for maturation promoting factor is an enzyme promotes the passage into M phase from the growth phase (G2 )
During the mitosis process the enzyme which breaks the cyclin gets activated and due to this level of cyclin gets decrease.
The decrease in the levels of the cyclin leads to a decline in the levels of MPF at the end of mitosis.
MPF is composed of cyclin and kinase. It lets the cell go from G2 stage to M stage. When the cell is going to anaphase, MPF inactivates. The decline of MPF activity at the end of mitosis is due to the degradation of cyclin. Option (C).
----------------------------
Many molecules regulate the cell cycle during the different stages of the mitosis process to make it possible.
There are too many factors interacting, activating, and deactivating to pass from one stage to another.
Cyclins are cell cycle regulator proteins that control the cell during the process of division. Different types of cyclins act on a different stages.
When the cell is going through one of the stages, the only cyclin in high levels is the one that is regulating that part of the cycle.
Once that stage is over, that cyclin concentration decreases, and the following one increases.
Kinases, Cdk, are enzymes that depend on cyclins and that remain inactive until cyclins are present.
The enzyme becomes functional when the cyclin binds it. Then, the kinase can accomplish its functions.
When the cyclin and the kinase are together, they compose the Maturation Promotor Factor, MPF.
MPF is composed of cyclin and kinase. MPF is in charge of letting the cell go from the G2 stage to the M stage.
The inactivation of MPF is due to the degradation of cyclin. As cyclin is destroyed, the MPF gets inactive.
Steps:
1) During the whole cell cycle, cyclin M remains at low levels.
2) When the cell is ready to pass from G2 to M phases, cyclin M increases its concentration and binds Cdk.
3) Together, these proteins compose the MPF that makes this transition possible.
4) Once the cell is in the M stage, MPF needs to decrease.
5) The factor autoregulates by activating another complex. The anaphase-promoting complex/cyclosome, APC/C.
6) When the cell is ready to go from metaphase to anaphase, the APC/C complex begins the cyclins M elimination process. The complex also activates separase to separate chromatid sisters while destroying cyclins M.
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Two pea plants heterozygous for the characters of pod color and pod shape are crossed. Draw a Punnett square to determine the phenotypic ratios of the offspring.
Answer:
I will attach a file with the punnett square
Explanation:
You have to write every possible combination of gametes for each individual. In this case, both individuals will have the same possible combination of gametes because they both are heterozygous for both traits. Then you have to make the crossing between each gamete and you get the punnett square.
A cross between pea plants heterozygous for pod color and shape produces a 9:3:3:1 phenotypic ratio, as predicted by a dihybrid cross Punnett square. This indicates 9 offspring would be green and round, 3 would be green and wrinkled, 3 would be yellow and round, and 1 would be yellow and wrinkled.
Explanation:In this cross scenario, we're considering two characters i.e., pod color and pod shape and the pea plants are heterozygous for both traits. A heterozygous plant can be denoted as GgRr, where 'G' and 'R' are dominant alleles for green color and round shape, and 'g' and 'r' are recessive alleles for yellow color and wrinkled shape.
To examine all possible combinations of these traits in the offspring, we use a type of Punnett square called a dihybrid cross. This square is 4x4 and it helps predict the genotypes and phenotypes of the offspring. The phenotypic ratio for a dihybrid cross where both parents are heterozygous for both traits is typically 9:3:3:1. This means 9 offspring will be green and round, 3 will be green and wrinkled, 3 will be yellow and round, and 1 will be yellow and wrinkled.
However, actual results can vary from these predicted ratios because the distribution of traits among offspring is determined by chance.
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What types of feedback are used in the body? Find examples
Answer:
Positive and Negative feedback
Explanation:
In positive feedback, the released product in the process allows the increase in the product. For example- during the time of child birth, crevix due to more pressure allows contractions and release of oxytocin. The hormone oxytocin causes more contraction.
In negative feedback, the released product causes decline in the level. For example, the temperature regulation mechanism, high temperature cause start sweating when there is temperature drop then low temperatures causes vasoconstriction and temperature increased again.
Mendel's second law is the Law of Independent Assortment. According to that law and according to other facts that Mendel discovered, what statement or statements are true in the following list?
a. genes behave like fluids rather than like separate particles
b. genes behave like separate particles rather than like fluids
c. the alleles of the different genes separate independently of one another during meiosis
d. both a. and c. are correct
e. both b. and c. are correct
Answer:
Option (c).
Explanation:
The Mendel's give the two most important laws to explain the transmission of the characters in the organism. Mendel is known as father of genetics and explained his work on the pea plant Pisum sativum.
The Mendel's law of independent assortment explains that in the combination of different genes the alleles of the genes separate or assort independently to one another during the meiosis process. The genes must be present on different chromosome to assort independently.
Thus, the correct answer is option (c).
Mendel's second law, the Law of Independent Assortment, supports that genes behave as separate particles and alleles of different genes separate independently during meiosis, making the answer both b. and c. are correct.
The question pertains to Mendel's second law, known as the Law of Independent Assortment. This law highlights how alleles of different genes separate independently of one another during the process of meiosis, leading to the gametes containing a mix of alleles. It refutes the concept of blending inheritance, where genes were thought to behave like fluids, and instead, supports the idea of particulate inheritance, where genes behave as discrete units or particles.
Therefore, the statements that are true according to Mendel's second law and his other discoveries are that genes behave like separate particles rather than like fluids, and the alleles of different genes separate independently of one another during meiosis. Hence, the correct answer is: both b. and c. are correct.
Which of the following is not considered evidence that supports the endosymbiotic theory? Mitochondria and chloroplast chromosomes are structurally similar to bacterial chromosomes. Chloroplast DNA and mitochondria DNA is an exact copy of bacteria DNA. Mitochondria and chloroplast replicate/reproduce in a manner similar to prokaryotic cells. The ribosomes of mitochondria and chloroplast resemble those of bacteria.
The incorrect evidence is that Chloroplast DNA and mitochondria DNA are exact copies of bacteria DNA, as they are merely highly related but not identical due to gene transfer to the host nucleus.
Explanation:The piece of evidence that does not support the endosymbiotic theory is the claim that 'Chloroplast DNA and mitochondria DNA is an exact copy of bacteria DNA.' While it is true that mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA) are highly related to bacterial DNA, they are not exact copies. Over time, many genes originally present in the mtDNA and cpDNA have been transferred to the host cell's nuclear DNA, meaning these organelles' genomes are now reduced in size compared to those of their bacterial ancestors.
Mitochondria and chloroplasts share several key characteristics with bacteria that support endosymbiosis: binary fission similar to bacterial replication, the structural similarity of their DNA to bacterial chromosomes, and ribosomes that resemble those found in bacteria. These characteristics, along with the additional evidence such as similar biochemistry and plasma membranes, corroborate the endosymbiotic origin of these organelles.
At the end of the Pleistocene, there are a series of extinctions in which the majority of large mammals go extinct. Why of these is a hypothesized cause of the extinction?
a. meteor impact
b. increased volcanism
c. glacial-interglacial cycles
d. human induced climate change
e. all of the above are hypothesized causes
Answer:
The correct option is: c. glacial-interglacial cycles
Explanation:
Pleistocene, also known as the Ice Age, is a geological epoch that is dated about 2.588 million to 11,700 years before present.
At the end of Pleistocene, the last glacial period ended and it also corresponds to the extinction of large mammals.
The cause of the extinction during Pleistocene is considered to be a combination of many factors such as human predation, climate change, interspecific competition, and unstable population dynamics.
Summarize the evidence showing that the sequence of nucleotides in a gene is colinear with the sequence of amino acids in a protein.
Answer:
A DNA is the genetic material of the organism which gets transferred to progeny controlling their traits. The DNA contains a sequence of nucleotides which codes for a protein called genes which provide instruction of the trait.
The DNA forms an mRNA molecule which by the process of Transcription and this mRNA molecule gets translated into the protein by Translation. Translation proceeds in the ribosomes where mRNA bases are studied by the ribosomes in the form of triplets called codons. Each codon codes for a specific amino acid which gets bonded to form a polypeptide.
Since the sequence of bases form codons which form the proteins in the same sequence as they are arranged on the mRNA, therefore nucleotides of the gene are collinear with the amino acids if the proteins.
Answer:
n
Explanation:
s
Some bases are attached to sugars whereas other bases are attached to phosphates.
a. True
b. False
Answer:
The correct answer will be option-false.
Explanation:
DNA is made up of repeating monomer units called nucleotides which form both the strand of the DNA. Each nucleotide is composed of a five-carbon sugar called deoxyribose, a phosphate group and four different types of nitrogenous bases.
The nitrogenous bases are of two types: purines with four nitrogen like adenine and guanine and pyrimidines with two nitrogen like thymine and cytosine.
According to the Chargaff rule, purine binds pyrimidine always in the DNA where adenine binds thymine and cytosine binds guanine.
Thus, false is the correct answer.
Describe how Mendel cross-fertilized and self-fertilized pea plants.
Pea plants have several visible differences, and since it is a common plant Mendel saw it as a perfect subject for his experiments, since pea have stamen and stigma these plants can self-pollinate, fertilizing the stigma with stamen's pollen, to prevent this, Mendel removed their stamen.
Cross-fertilization is the process in which Mendel collected pollen from a plant and transferred it to another plant with its stamen's previously cut.Self-fertilization is when the plant's pollen fertilizes itself.
I added an illustrative image, I hope you find this information useful! Good luck!
Final answer:
Mendel conducted experiments on pea plants by cross-fertilizing and self-fertilizing them to study inheritance patterns. Cross-fertilization involved manually transferring pollen between different true-breeding plants, while self-fertilization occurred naturally in subsequent generations.
Explanation:
Gregor Mendel is famed for his experiments on pea plants that formed the basis of modern genetics. To carry out his studies on inheritance, Mendel performed both cross-fertilization and self-fertilization techniques on true-breeding plants, primarily the species Pisum sativum. For cross-fertilization, Mendel manually transferred pollen from the anther (male reproductive organ) of one pea plant to the stigma (female reproductive organ) of another, ensuring that the two parent plants had different traits. Before doing this, he removed the anthers from the recipient plant to prevent self-fertilization and ensure controlled breeding.
When Mendel's cross was successful, he obtained what he termed as the P or parental generation. He would then cultivate the resulting seeds to produce the first generation of offspring, known as the F1 generation. After examining the traits in the F1 generation, Mendel permitted these plants to self-fertilize, meaning they produced seeds using their pollen, creating the F2 generation. This meticulous approach allowed Mendel to discover the inheritance patterns that would lead to his famous laws of heredity.
These are the only viruses large enough to be seen under the light microscope:
A) Papillomavirus
B) Poxvirus
C) Herpes virus
D) Adenovirus
Answer:
B) Poxvirus
Explanation:
Poxviruses, a type of DNA-viruses, typically infect animal cells. They are particular big among viruses, with sizes ranging from 200 to 400nm. Their extremely large size (considering they are viruses) allow them to be visualized under light microscope.
The effect of the Y chromosome on gonadal sex determination is mediated by a gene called ___________
Answer:
SRY
Explanation:
Sex determination in mammals including humans is genetically and hormonally controlled.
Genetically gonadal sex determination is mediated by a gene called SRY. This gene is known as the mammalian Y-chromosomal testis-determining gene. It induces sex determination in males.
Recent studies revealed that SRY plays an important role in inducing Sertoli cells differentiation. The Sertoli cells, in turn, guide testis formation.
Therefore, in males, differentiation of testis is switched on by expression of the Y-linked SRY gene.
In prokaryotes, a search for genes in a DNA sequence involves scanning the DNA sequence for long open reading frames (that is, reading frames uninterrupted by stop codons). What problem can you see with this approach in eukaryotes?
Final answer:
Scanning for long open reading frames to find genes works in prokaryotes due to their less complex genome organization and lower noncoding DNA content. This method is not as effective in eukaryotes, which have more noncoding DNA, individual promoters for each gene, and complex chromatin structures that hinder straightforward gene identification.
Explanation:
In prokaryotes, scanning a DNA sequence for long open reading frames (ORFs) is a logical method for gene identification because prokaryotic genomes have less noncoding DNA and often organize genes encoding proteins of related functions into operons. This means that genes are grouped together, have a single promoter, and can be transcribed into polycistronic mRNA, making it easier to identify coding sequences.
However, using this approach in eukaryotes imposes challenges. Eukaryotic DNA contains a much higher percentage of noncoding DNA, which means that scanning for long ORFs would yield many false positives, as noncoding introns and other noncoding elements could be mistakenly identified as genes. Additionally, eukaryotic genes are typically monocistronic, each gene having its own promoter, and exist in a complex chromatin structure, which makes simple scanning insufficient.
Another complexity in eukaryotic genomes is that promoters can be located within genes or far away from them, both upstream or downstream. This means that the regulatory sequences are not always neatly placed before genes, as seen in prokaryotes. Also, eukaryotic DNA is wrapped around histone proteins, forming nucleosomes, which complicate direct access to the DNA sequence for transcription and therefore, gene identification.
Which of these are true regarding eukaryotes? (choose all that apply)
a. Chromosomes each have one origin of replication
b. During replication there is both a leading strand and a lagging strand
c. Each replication bubble has two replication forks
d. Replication is stopped by the Ter proteins.
Answer:
b. During replication there is both a leading strand and a lagging strand .
c. Each replication bubble has two replication forks.
Explanation:
Eukaryotic chromosomes have multiple origins of replication to replicate the long chromosomes at a higher rate.
The two DNA strands have opposite polarity, that is, 5' end of the one DNA strand is present opposite to the 3' end of the other DNA strand. DNA replication occurs only in 5' to 3' direction and the direction of the movement of the replication fork is also 5' to 3' direction.
To allow the DNA replication in 5' to 3' direction on both strands, one strand is replicated discontinuously in the direction opposite to the movement of the replication fork.
The discontinuously replicated strand is lagging strand while the other one is the leading strand.
DNA replication in eukaryotes occurs bidirectionally as two replication forks are formed at each replication bubble, one at each end of the replication bubble.
The presence of multiple origins of replication and the bidirectional process allows the replication of large eukaryotic DNA at a considerable fast speed.
Final answer:
In eukaryotic cells, DNA replication involves multiple origins of replication which allow for the efficient copying of their typically linear chromosomes. b) Both leading and lagging strands are synthesized, with c) replication proceeding with two forks per bubble.
Explanation:
The question pertains to the characteristics of eukaryotic DNA replication. In eukaryotic chromosomes, which are typically linear, you would find multiple origins of replication. DNA replication in eukaryotes involves b) both a leading strand and lagging strand. Each new double helix at the replication fork moves bi-directionally, creating c) two replication forks per replication bubble. Contrary to an option given in the problem, replication in eukaryotes is not stopped by Ter proteins; this is a mechanism found in bacterial DNA replication.
Each chromosome in a eukaryotic cell has many thousands of origins of replication, initiating replication at multiple points to ensure the DNA can be copied efficiently within the necessary timeframe. The replication bubbles formed by the origins coalesce as replication forks meet, resulting in the duplication of DNA. The replication process includes enzymes like DNA polymerases, helicases, and ligases, and is efficient thanks to the orchestrated function of these proteins.
Characteristics of Azotobacter Azotobacter is a genus of bacteria that live in soil and have the following characteristics: They are bacilli. They are gram-negative. They are obligate aerobes. They can fix nitrogen. (Unlike some other nitrogen-fixing bacteria, which associate with the roots of plants, Azotobacter species are free-living.) Select the four statements that are true for bacteria in the genus Azotobacter. They are poisoned by O_2. They appear purple after Gram staining. They have a relatively thin layer of in their cell wall. They require amino acids or other organic molecules as a source of nitrogen. They use O_2 for cellular respiration. They can carry out anaerobic respiration in an environment that lacks O_2. They are shaped like rods. They have the appearance of coils or corkscrews. They can convert atmospheric nitrogen to ammonia.
Answer:
- They have a relative thin layer in their cell wall
-They use O2 for cellular respiration
-They are shaped like rods
-They can convert atmospheric nitrogen to ammonia
Explanation:
The genus Azotobacter comprises a group of species of bacilli (rod-shaped), strict aerobics (they need oxygen to live) and gram-negative, which is to say they have a thin layer of peptidoglycan in their cell wall, that when performing a gram staining would appear pink. These bacteria can fix nitrogen, that is, convert atmospheric nitrogen (N2) into ammonia (NH3), more available to metabolize by most organisms, a process essential to life.
Describe the relationship between linkage groups and chromosomes.
Answer:
The relationship between linkage groups and chromosomes is that the fist ones are all of the genes on a single chromosome.
Explanation:
Linkage groups are a group of genes present at different loci on the same chromosome. So a chromosome constitutes one linkage group that is inherited as a group during cell division. The haploid number of chromosomes shows the maximum number of linkage groups.
A linkage is the tendency that genes have to remain together during inheritance in the original combination.
Answer:
When genes are located on different chromosomes they segregate independently, but when they are located on the same chromosome, there is no segregation and they go together to the same gamete. This process is called gene binding.
Explanation:
When genes are located on different chromosomes they segregate independently, but when they are located on the same chromosome, there is no segregation and they go together to the same gamete. This process is called gene binding.
In the process of independent segregation, an AaBb individual produces 4 types of gametes, at a rate of 25% each. When a case of gene binding occurs, the individual AaBb produces only AB and ab gametes, at a rate of 50% each.
The link between the genes may be incomplete, because during meiosis prophase 1, when homologous chromosomes are paired, exchanges of parts occur between sister chromatids in a process called crossing-over or permutation. These exchanges result in the formation of recombinant gametes, which are chromosomes with new allele combinations.
If there was no recombination in these genes, the proportion of gametes formed by a double heterozygote would be 50% AB and 50% ab. When recombination occurs, a small proportion of recombinants are observed in the progeny.
What is the nature of "second signal molecules" in signaling pathways?
Answer:
The target receptor is expressed in the membrane, the activity of the receptor can instigate the production of small molecules known as the secondary messengers that coordinate and initiate the intracellular signaling pathways. For example, cyclic AMP is a secondary signal molecule.
When the signal molecules stimulate the receptor, the signal is carried into the cell generally by means of secondary messengers.
Second signal molecules, also known as second messengers, are crucial components of cell signaling pathways. They relay the signal from the cell surface receptor to the interior of the cell, helping to propagate or even amplify the signal for a larger cellular response. Examples include cyclic AMP, inositol trisphosphate, and calcium ions.
Explanation:The nature of "second signal molecules" in signaling pathways refers to a significant part of cell communication. These molecules are often termed second messengers because they relay the signal from the receptor on the cell surface, which is first to identify the signaling molecule, to the interior of the cell. The function of these intermediates is to propagate the signal and sometimes amplify the signal to produce a larger cellular response. Biologically essential second messengers include cyclic AMP (cAMP), inositol trisphosphate (IP3), and calcium ions.
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