Answer:
D
Explanation:
A cell and its organelles are usually transparent hence hard to discern without staining. There are different staining techniques that are useful for viewing various type of cells and organelles depending on which stain they pick up well. In this case of an onion, the starch molecules in the onion will take up the iodine and improve visualization. This due to the fact that iodine molecules get emended in the structure of the amylose and amylopectin molecules of starch causing starch molecules to turn blue lack (due to a change in light absorption spectra of the complex).
Final answer:
Josey should try applying a stain, such as iodine, to her onion sample to see the cells in detail. Using a thicker piece of onion, placing the sample in a vacuum, or adding a drop of water can also improve visibility, but applying a stain is the most effective solution.
Explanation:
To see the onion cells in detail, Josey should try applying a stain to her sample. Stains like iodine can help to make the cells more visible under the microscope. By adding a stain, the cells will appear darker or have a different color, making it easier to see their structures and details.
Using a thicker piece of onion for the sample or placing the sample in a vacuum will not help Josey see the onion cells in detail. A thicker piece of onion will not necessarily enhance the visibility of the cells, and placing the sample in a vacuum is not necessary for observing cells under a light microscope.
Adding a drop of water to the sample can actually help improve the visibility of the cells. Water can help to enhance the contrast between the cells and the microscope slide, making the cells easier to see.
What is the significance of the industrial practice of waiting for cultures to enter the stationary phase of growth before harvest?
a. An optimal combination of primary and secondary metabolites is being produced.
b. Secondary metabolites are often the desired product, and are only produced in stationary phase.
c. The desired primary metabolites are produced in stationary phase.
d. The cells are at peak metabolic activity.
e. Potential toxins from log phase growth have been depleted
Answer: b. Secondary metabolites are often the desired product, and are only produced in stationary phase.
Explanation:
The secondary metabolites are the organic compounds that are produced by the microbes such as bacteria, fungi and even by the plants. These are not involved in the growth, development and reproduction of the organisms. But they can provide a advantage for the survival. It helps in plant defense against the process of herbivory and other interspecies defense. Humans take the secondary metabolites from these organisms in the form of medicines, pigments, and recreational drugs.
The secondary metabolites are produced only in the stationary phase of growth. Thus it is significant for the collection of these secondary metabolites in the stationary phase.
What are the two types of orientation behavior? Provide an example of each.
Answer:
Two types of orientation behavior are as follows:
Taxis behavior:
This is a type of orientation behavior that mainly occur in response towards the external stimulus. Taxis may be positive (movement towards the stimulus) or negative ( movement away from the stimulus). Different types of taxis behavior are phototaxis, aerotaxis, chemotaxis and magnetotaxis.
Kinesis:
Kinesis may be defined as a type of orientation behavior that can change the complete movement or orientation of the organism. Kinesis is a random movement and organism can move in either direction. Different type of kinesis are klinokinesis and orthokinesis.
A yeast associated with leukemic patients that produces arthrospores is
A) Cyptococcus neoformans
B). Trichosporon species
C) Candida parapsilosis
D) Candida glabrata
Answer: B). Trichosporon species
Explanation:
The Trichosporon is the genus of the anamorphic fungi. In includes the yeast that exhibit no sexual states. These are known for their production of the arthrospore an asexual mode of reproduction in these fungi. These can be found in the soil, or in skin microbiota of the animals and humans. The Trichosporon species is known for severe infections in individuals with weak immune system.
Which of the following is NOT a function of Sertoli cells?
A. Synthesis of inhibin.
B. Removal of damaged germ cells.
C. Production of seminiferous tubular fluid.
D. Production of primary spermatocytes.
E. Formation of Blood-testis barrier
Sertoli cells do not produce primary spermatocytes (option D); instead, they support spermatogenesis, create a blood-testis barrier, produce tubular fluid, remove damaged germ cells, and secrete inhibin.
The function that is NOT a function of Sertoli cells is D. Production of primary spermatocytes. Sertoli cells, also known as sustentacular cells or sustentocytes, indeed have several important roles in sperm production within the seminiferous tubules of the testes. They also form the blood-testis barrier, produce substances such as inhibin that regulate spermatogenesis through a negative feedback mechanism, create, seminiferous tubular fluid, and remove damaged germ cells. However, the production of primary spermatocytes is not one of their functions. Primary spermatocytes are derived from germ cells and undergo meiosis to form spermatids, which are then transformed into mature spermatozoa. The Sertoli cells support this process but do not produce the spermatocytes themselves.
Name the three essential active site residues of chymotrypsin and describe how each is involved in the catalytic mechanism.
Answer:
The active site residues include Serine, Histidine and Aspartatic acid
Explanation:
The catalytic triad at the active site of Chymotrypsin includes Ser-105 (Serine), His-57 (Histidine) and Asp-102 (Aspartic acid).
His-57: Deprotonates and polarizes Ser-105 so that it is able to react with substrate.
Asp-102: The carboxyl group of Asp-102 hydrogen bonds with the R-group of the His-57 which facilitates the deprotonation of Ser-105.
Ser-105: The strong nucleophile of serine attacks the substrate leading to hydrolysis.
Which of the following statements is true about mutations induced by radiation?
a. xrays, cosmic rays, and UV rays are all classified as ionizing radiation
b. ionizing radiation results in raising electrons to an atom's outer orbitals, a state referred to as excitation.
c. in mammals, chronic irradiation is as effective in inducing mutations as acute irradiation
d. UV radiation results in the formation of purine dimers and purine hydrates
e. xrays can result in gross changes of chromosome structure, such as large deletions, duplications and inversions.
Answer:
The correct answer is option e.
Explanation:
X-rays refers to the ionizing radiation exhibiting shortest wavelengths and possessing the tendency to pass through the tissues. This tendency of passing through the tissues on getting exposed to X-rays even for brief duration will lead to displacement of electrons from the orbital of molecules and atoms like witnessed in chromosomes.
X-rays are not stable and possess high energy and when this energy passes on to the electrons, it gets displaced resulting in the modifications of the structure of nucleic acid bases in the DNA resulting in chromosomal modifications like inversion, transversion, duplication, and deletion mutations.
Midphalangeal hair (hair on top of the middle segment of the fingers) is a common phenotype caused by a dominant allele M. Homozygotes for the recessive allele (mm) lack hair on the middle segment of their fingers. Among 1000 families in which both parents had midphalangeal hair, 1853 children showed the trait while 209 children did not. Explain this result.
Answer:
40% families have heterozygous genotype (Mm).
Remaining 60% of the families will have one parent with homozygous genotype (MM)
Explanation:
If both the parents are heterozygous, then the ration of children without hair to those with hair is 1:3
So, parents with genotype Mm and Mm will produce 209 kids without hair and 209 X 3 i.e 627 kids with hair.
Thus, nearly 40% families have heterozygous genotype (Mm). And the remaining 60% of the families will have one parent with homozygous genotype (MM)
Final answer:
The presence and absence of midphalangeal hair among the children of 1000 families can be explained by Mendelian inheritance, where both parents are likely heterozygous, resulting in a 3:1 ratio of children displaying the trait versus those who do not.
Explanation:
The observation that among 1000 families, both of which have parents displaying midphalangeal hair, resulted in 1853 children with the trait and 209 without can be explained by the Mendelian inheritance pattern. Since midphalangeal hair is caused by a dominant allele (M), and the absence of it by homozygous recessive (mm), we can infer that both parents were heterozygous (Mm) for the trait.
Using a Punnett square, we can predict the possible offspring from two heterozygous parents:
MM (has midphalangeal hair)
Mm (has midphalangeal hair)
mM (has midphalangeal hair)
mm (lacks midphalangeal hair)
This results in a 3:1 ratio of children with the trait to those without, closely reflected in the provided offspring count of 1853 showing the trait and 209 not showing it.
The slight variation from the expected 3:1 ratio can be attributed to the large sample size and possible environmental influences or misclassification. Essentially, this example demonstrates the classic Mendelian inheritance of a trait determined by a single gene with two alleles, where one is dominant over the other.
Which sequence best describes the passage of sperm? 1. Seminiferous tubules. 2. Vas deference. 3. Epididymis 4. Ejaculatory duct 5. Urethra.
A. 3,1,2,4,5
B. 1,3,2,4,5
C. 5,4.2,3,1
D. 1,3,4,2,5
E. 3,1,4,2,5
What is the fastest way to administer nicotine to the brain?
a. Intravenous route (IV)
b. Snorting
c. Chewing
d. Smoking
e. IV and smoking are equally fast
Answer:
d. Smoking
Explanation:
Nicotine is a chemical found in many plants such as tobacco. It is one of the 4000 chemicals that tobacco presents and the main component that acts in the brain.
This chemical is absorbed through the skin and lining of the mucosa of the nose and mouth, or in the lungs by prior inhalation. Nicotine can quickly reach the bloodstream and brain and reach maximum levels. The action of smoking cigarettes causes nicotine to reach the brain in just 10 seconds after inhalation. Although the acute effects dissipate in a few minutes, they cause the need to continue the intake of the substance (addiction)
DNA has a charge associated with it. What functional group that carries a charge is included in DNA, and how do we use the charge to our advantage while doing gel electrophoresis? How does this relate to using the phrase "run to the red" while performing gel electrolysis?
Answer:
DNA is made up of sugar-phosphate backbone and the phosphate in the DNA contains the negative charge, therefore, DNA is a negatively charged molecule present in the nucleus.
This negative charge is very important in separating the DNA according to their charge and size during gel electrophoresis. During gel electrophoresis DNA of different size is run on an agarose gel in the presence of current and DNA fragments move toward positive charge due to negative in nature.
Small size DNA moves fast through the gel large size DNA moves slow towards negative pole, therefore, separating the DNA according to their size. In gel electrophoresis, red pole is positive pole and the black pole is negative so runs to the red phrase is signifying that the DNA is always run towards the red pole.
Estrogen is most likely to exert its effect by regulating
a) protein kinases.
b) phospholipase C.
c) expression of genes and production of
specificproteins.
d) cyclic AMP
e) Ca2+.
Answer:
c) expression of genes and production of specific proteins.
Explanation:
Estrogen is a lipid-soluble steroid hormone that diffuses through the lipid bilayer of the plasma membrane of its target cell. The hormone binds to its nuclear receptor and receptor-hormone complex then alters the expression of particular genes.
It triggers transcription of specific DNA sequences into mRNA which in turn enters the cytoplasm and serves as a template for synthesis of specific proteins.
Estrogen is the female sex hormone and stimulates development of secondary sexual characters in females as well as required for maturation of egg.
Group of similar cells is called ___________
a. organelles
b. organ
c. tissue
d. organ system
Answer:
C. Tissues
Explanation:
Tissues are the group of similar cells all of that perform specific function. The cells that make a tissue mostly have a common origin and function together to perform some specialized tasks.
For example, the human body consists of four basic types of tissues. Muscular tissues are one of the tissue types of the human body. The cells that make the muscular tissues are specialized for contraction and force generation to support the movement of body parts.
The largest unit within which gene flow can readily occur is a
a. population c. genus.
b. species d. hybrid.
Answer:
a. population
Explanation:
Gene flow cannot occur in hybrids because 99.9% of the time hybrids offspring are not fertile.
At genus level is not possible either because a hybrid is a cross breed at the genus level (horse-donkey).
A population is a group of species of 1 kind. A population of donkeys.
Which of the following is a plant adaptation to living in a cold climate?
a. Requiring burning
b. Vernalization
c. Seed coat
d. Endosperm
Answer:
b. Vernalization
Explanation:
Vernalization is a phenomenon in which plants require low temperature for the flowering. There is either qualitatively or quantitatively dependent on exposure to very low temperature. This process is known as vernalization. Vernalization defines especially to the promotion of flowering by a period of low climate. For example; Vernalisation occurs in biennial plants. Biennials are monocarpic plants which normally flower and may die in the second season. Some common examples of biennials are carrots, Sugarbeet, cabbages, etc.
The outer layer of a virus is called a capsid and is made of protein.
a. True
b. False
Answer:
a. True
Explanation:
Viruses are nor living nor non-living things. They do not metabolize, and only consist of nucleic acid in the inside of a protein cover which protects it. This proteinous layer is known with the term capsid, and is usually formed by units of certain proteins called capsomeres. Besides protection, these proteins serve as the structures that actually allows viruses contact and adhere to host cells during infection, that's why they are key components for the viruses success.
In his work with pneumonia-causing bacteria and mice, Griffith found that
a. the protein coat from pathogenic cells was able to transform nonpathogenic cells.
b. heat-killed pathogenic cells caused pneumonia.
c. some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
d. the polysaccharide coat of bacteria caused pneumonia.
Answer:
Option (c).
Explanation:
Griffith is known as the father of transforming principle. He worked on the virulent and a virulent bacteria that causes pneumonia. He done his experiment on different heat conditions.
When he heat killed the S strains of bacteria and R strains of bacteria into the mice, the mice was killed. He concluded that there was some substance or transforming principle converts the non pathogenic bacteria into the pathogenic strain.
Thus, the correct answer is option (c).
Which of these occurs first?
a. Helicase unwinds DNA
b. Sliding clamp binds around DNA
c. DnaA binds at the origin of replication
d. DNA pol III copies DNA
Answer:
The correct answer is a. Helicase unwinds DNA
Explanation:
DNA replication is a process in which DNA make it's own copy. There are several enzymes and factors which access the DNA replication process like helicase, primase, SSB protein, DNA polymerase etc.
The first step in DNA replication is the unwinding of double stranded DNA which is accomplished by an enzyme called Helicase. Helicase opens up the double stranded DNA at replication fork by breaking the hydrogen bond between the nucleotides of complementary strands.
This provides a single stranded template for DNA polymerase to form a new complementary strand. In E. coli Dna B is the primary helicase and in humans the primary helicase is MCM( minichromosome maintenance protein complex).
Why are there villi in the small intestine? How do they improve absorption?
Answer:My answer is in the picture
XD
Explanation:Hope this help
in a pea plant that is heterozygous for seed color what
proportionof gametes will carry the recessive allel?
3/4
1/2
1/4
none above.
Answer:
1/4.
Explanation:
The Mendel is known as father of genetics. He explained the concept of dominance, law of segregation and law of independent assortment while working on the pea plant.
The cross between the heterozygous seed color (Ss × Ss), result in the 3/4 dominant phenotype ( SS, Ss and Ss ) and 1/4 recessive phenotype with alleles ss.
Ss × Ss
progeny obtained are SS, Ss, Ss and ss.
Thus, the correct answer is option (3).
How can mutations change the gene pool of a population?
Answer:
Explanation:
The changes in the gene pool occurs from the one generation to another this process is called as the microevolution. The allele frequencies in the gene pool change due to many processes such as gene flow, natural selection, genetic drift, and mutation. In mutation the genetic variations occurs in the genome of the organisms due to change in the genetic makeup of the organisms new traits are produced which are passed on to the new generation and this brings change in diversity of genes in the gene pool.
George W. Beadle and Edward L. Tatum refined the concept of the gene to state which of the following original ideas?
a. one gene - one enzyme
b. one gene - one metabolic block
c. one gene - one transcript
d. one gene one polypeptide
e. one gene - one allele
Answer:
one gene - one enzyme.
Explanation:
The Garrod's explain the hypothesis one gene enzyme and one enzyme. According to this hypothesis, the single gene codes for the single enzyme that plays an important role in the body metabolism.
The Garrod's hypothesis was experimentally performed by the George W. Beadle and Edward L. Tatum. They performed the biochemical studies and genetic tests on Neurospora to explain the one gene one enzyme hypothesis.
Thus, the correct answer is option (a).
What are the four factors that determine a population's growth rate?
a. Birth rate, death rate, doubling time, and carrying capacity
b. Birth rate, death rate, doubling time, and compounding
c. Birth rate, death rate, carrying capacity and emigration rate
d. Birth rate, death rate, immigration rate, and emigration rate
e. Birth rate, death rate, compounding, and immigration rate
Answer:
I think it's d
Explanation:
Which of the following are phagocytic?
a. neutrophils only
b. lymphocytes only
c. monocytes and macrophages
d. all of these cells are phagocytic
e. macrophages only
f. monocytes, macrophages and neutrophils
g. monocytes only
Answer:
The correct answer is option F. monocytes, macrophages and neutrophils.
Explanation:
Phagocytic cells are the cells that engulf harmful substances or foreign particles, bacteria and other dead cells. These cells destroy them by engulfing the foreign particles and degrade them by chemical releases.
The phagocytic cells include - monocytes, macrophages, neutrophils, and dendritic cells. All these three types of cells are further divided. The neutrophils are the first cell to appear at the site of the infection or injury.
Thus, the correct answer is option F. monocytes, macrophages and neutrophils.
Muscle cells in oxygen deprivation convert pyruvate to ______ and in this step gain _______
A) lactate ATP
B) alcohol... CO2
C) alcohol..ATP
D) ATP... NAD+
E) lactate ..NAD+
Answer: E) lactate ..NAD+
Explanation:
In conditions of oxygen deprivation, cells can't undergo normal cellular respiration and must rely on other processes to obtain energy.
Muscle cells in particular, under anaerobic exercise, do not obtain enough oxygen to produce the energy needed and end up obtaining energy form a process different than cellular respiration: lactic fermentation.
Lactic fermentation turns a molecule of pyruvate into a molecule of lactate, at the same time it turns NADH into NAD+.
Predict the change in leukocyte count in a patient suffering from leukemia (cancer involving leukocytes)
Answer:
Leukemia may be defined as the cancer of the blood cells especially white blood cells. The leukemia may occur due to mutation or may also occur due to the biological agents.
Leukemia causes the abnormal and uncontrolled growth of the blood cells. These white blood cells are unable to fight with infections and causes the bone marrow to produce impair formation of blood cells. The patient shows abnormal growth and large count of leukocytes.
Propose a hypothesis for the evolution of life on earth from single-celled organisms to multicellular organisms. What is the most significant step in the evolution of multicellularity?
Answer:
there are tree hypothesis
Explanation:
There are several mechanisms by which multicellularity could have evolved:
1. A group of cells were added in a slug-shaped mass called grex, which was moved as a multicellular unit, as the Myxomycota do.
2. The primitive cell suffered an incomplete division of the cell nucleus generating a cell with multiple nuclei or syncytium. Next, membranes formed around each nucleus and the space was occupied by organelles. This resulted in a group of cells connected in an organism, an observable mechanism in Drosophila.
3. Daughter cells did not separate after cell division, resulting in a conglomeration of identical cells in an organism, which later developed specialized functions. This is observed in embryos of plants, animals and colonial cyanoflagellates.
Should read more about the topic here, google it:
Multicellular development in a choanoflagellate; Stephen R. Fairclough, Mark J. Dayel and Nicole King
In a Single-Cell Predator, Clues to the Animal Kingdom’s Birth
Name one enzymatic step of the TCA cycle wherein a universal electron carrier (in its reduced form) is a product of the reaction: ____________
Answer:
Oxidation of Malate to Oxaloacetate by Malate Dehydogenase
Explanation:
An electron carrier is able to accept and donate electrons in a reaction. The most popular is NADH. NADH in its oxidized form is NAD+. NAD+ received two (2) electrons and an H+ to be reduced to NADH. Other electron carriers are NADPH & FADH₂
There are several steps in the TCA where NAD+ is reduced to NADH by accepting an electron. One of this step is the last step where malate is oxidized and is converted back to oxaloacetate the beginning molecule of the cycle.
Testosterone and its derivative dihydrotestosterone prompt the Mullerian ducts to develop into male accessory structure, epididymis, vas deference and seminal vesicle.
a. True
b. False
Answer:
The given statement is false.
Explanation:
The paramesonephric ducts or the Mullerian ducts refers to a paired ducts of mesodermal in origin found in the embryo. They run sideways down the urogenital ridge and culminates at the Mullerian eminence in the embryonic urogenital sinus.
The Mullerian ducts are the elemental organ of the female reproductive tract. They further divide to produce the uterus, the fallopian tubes, the superior part of the vagina, and the uterine cervix. A wide array of abnormalities can take place when this system gets hampered.
Which of the following diseases is more likely to occur through contact with contaminated water in industrialized countries than in non-industrialized countries?
a. hepatitis A
b. typhoid fever
c. legionellosis
d. hepatitis B
e. tuberculosis
Answer:
The correct answer is option b, that is, typhoid fever.
Explanation:
Typhoid refers to an infection caused by bacteria, which can cause high fever, vomiting, and diarrhea. It can be deadly. It is caused by the bacteria S. typhi. The infection generally passes due to consumption of contaminated water and food. It is more common in places where maintenance of hygiene is less frequent.
The condition generally causes due to the spreading of the bacteria via drinks, food, and drinking water, which gets contaminated with fecal waste. The condition also spreads if contaminated water is used for washing vegetables and fruits.
We can be sure that a mole of table sugar and a mole of vitamin C are equal in their
a.mass c. number of atoms.
b.volume d. number of molecules
Answer:
The correct answer is option d, that is, the number of molecules.
Explanation:
Mole is illustrated as the given mass of the substance divided by the molecular mass of that substance. A mole of table sugar and a mole of vitamin C are not equivalent in mass. Volume is directly equivalent to mass. Mass can be different, thus, the volume can also be different.
The vitamin C and sugar are the compounds, which are formed of distinct elements combined in the particular molecular ratio. Thus, the number of atoms cannot be similar, also the mass and volume will not be similar for both vitamin C and sugar.
One mole of a substance comprises 6.023 * 10^23 molecules. This is called Avagadro's number. This is similar for all the components, hence, one mole of vitamin C and one mole of table sugar comprise a similar number of molecules.