Answer:
The cause of the current mass extinction is the anthropic activity. The consumption of fossil fuels, ocean acidification, pollution, deforestation and forced migration threaten life and have caused the disappearance of many species.
Final answer:
The sixth mass extinction differs from past events as it is caused by human actions, including habitat destruction, pollution, and overexploitation of species, marking a significant shift from natural catastrophic events to anthropogenic impacts.
Explanation:
The cause of the current, or sixth mass extinction, is significantly different from those of the past. While past extinctions were largely due to major geologic and climatic events, the sixth extinction is directly attributable to human actions. These actions include habitat destruction, overexploitation of species, pollution, and the introduction of invasive species, all of which have dramatically increased the rate of species extinction.
Unlike previous mass extinctions that were caused by events such as asteroid impacts or massive volcanic eruptions, the current crisis is the result of the activities of Homo sapiens, especially since the onset of the industrial revolution.
How many ATP are generated in the electron transport chain?
o2
O4
32
36
Answer:
32
Explanation:
A chemical imbalance in the body can cause the heart to stop pumping blood, which in turn will cause other tissues and organs to cease functioning. This observation supports the view that
Answer:
all levels of organisation within an organism are interdependent
Explanation:
An organism has different levels of organization within itself that, the levels are s follows: cell ----> tissues----> organs----> organ systems and there are further different organ systems present within an organism.Even though the organisms have a different level of organization, still there is an interdependence amongst these levels and all these different levels have to coordinate and work together so that the body can function normally. Therefore, a chemical imbalance in the body which may occur due to the nervous/endocrine system can cause the heart to stop pumping blood which is, in turn, a part of the cardiovascular system and this may further affect other tissues and organs and these may stop functioning. Thus this clearly shows how different levels coordinate and work to carry on norma functioning of the body. Cells contains parts known as organelles. These parts are specialized. What does that mean
Answer:
The answer below
Explanation:
What means that organelles are specialized?
Cells contains several kinds of organelles which help it to accomplish all the functions the cell needs. The cell is similar to us, we have different organs to do all our functions, the organelles are specialized in different activities to do all the functions the cells needs to be healthy. For example it has a membrane to protect and isolate from the environment, it has several mitochondria to generate energy or it has a nucleus to control all the activities. If the organelles weren't specialized, the cell couldn't accomplish all its functions.
Specialization refers to the process by which a structure becomes differentiated for a particular function. When a female ovum is fertilised by sperm, a zygote is formed which grows by mitosis. As it grows into am embryo then foetus, these cells undergo specialization as they form different tissues and organs which all play different roles to ensure the proper functioning of the body. Similarly, as organs and tissues cells undergo further specialization, in terms of organelles. Each cell contains organelles which serve different purposes, the nucleus controls cellular activity, mitochondria provides energy in the form of ATP, cytoplasm which provides the environment for metabolic reactions and ribosomes for protein synthesis ( to name a few). Each organelle uniquely specialized for its intended purpose and all reliant on each other.
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In an isotonic contraction, the muscle ________. A. rapidly resynthesizes creatine phosphate and ATP B. does not change in length but increases tension C. never converts pyruvate to lactate D. changes in length and moves the "load"
Answer:
Option D " changes in length and moves the "load"
Explanation:
What means ' isotonic contraction' ?
⇒ Isotonic contractions maintain constant tension in the muscle as the muscle changes length.
This means that option B "does not change in length but increases tension" doesn't apply. (This is isometric)
Option A says : " Rapidly resynthesizes creatine phosphate and ATP
Creatine phosphate breakdown is the most rapid method available to resynthesize ATP. The next fastest is glycolysis followed by aerobic metabolism in the tricarboxylic acid cycle (Krebs' cycle).
Option C says " never converts pyruvate to lactate".
Pyruvate is converted to lactate in anaerobic conditions, by the enzyme Lactate dehydrogenase. If pyruvate never gets converted to lactate it means this enzyme is missing.
Option D says :"Changes in length and moves the load. This is the definition of an isotonic contraction. So option D is correct !
An isotonic contraction is when the muscle changes in length to move a load, maintaining constant tension, which is different from isometric contractions where muscle length remains unchanged.
Explanation:In an isotonic contraction, the muscle changes in length and moves the "load". Unlike isometric contractions where muscle length does not change, isotonic contractions involve a change in muscle length while maintaining constant tension throughout the contraction. There are two types of isotonic contractions: concentric, where the muscle shortens, and eccentric, where the muscle lengthens. During a concentric isotonic contraction, for example, the biceps brachii muscle contracts to lift a weight, shortening as it does so and decreasing the angle of the elbow joint. Conversely, during an eccentric contraction, the muscle lengthens while lowering a weight in a controlled manner, and the angle of the elbow joint increases.
In an isotonic contraction, the muscle changes in length and moves the 'load'. This means that the muscle contracts and shortens, causing movement.
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PICTURE IS THE QUESTIONNN? THE PICTURE/SCREENSHOT is the questions and Question 1 has a picture to the question.
here are the answer choices if you can see them.
Question 1: A scientist observed that during the course of a chemical reaction in a tissue culture of animal muscle cells, the number of ATP molecules produced was greatly reduced. What did the scientist most likely hypothesize from the observation?
a
oxygen availability became limited
b
oxygen availability increased
c
carbon dioxide availability increased
d
carbon dioxide availability became limited
Question 2: Cells store energy when?
a
the third phosphate group breaks off from an ATP molecule.
b
a third phosphate group is bonded to an ADP molecule
c
they break down sucrose to glucose and fructose.
d
ions are released into the bloodstream.
Q1= the answer I think should be A
Q2= the correct answer B
Answer:
The correct answer will be option-
1. Option-A
2.Option-B
Explanation:
Case I
The production of ATP molecules in the animal cell takes place through a complex process called cellular respiration. The cellular respiration leads to the breakdown of the glucose molecule in the presence of oxygen which is utilized as an electron acceptor in the electron transport chain.
Since the ATP level decreased in the tissues indicated that the tissues are not getting enough oxygen molecule. Thus, option-A is the correct answer.
Case II
The cells store the energy molecule in the form of the ATP molecule which is formed by Phosphorylation or adding the phosphate group to the ADP molecule in the presence of energy provided by the movement of H⁺ ions.
Thus, Option-B is the correct answer.
All of the following are properties of membranes EXCEPT:
a. supramolecular assemblies.
b. define boundaries of cellular components.
c. spontaneous assemblies resulting from hydrophobic interactions.
d. identical protein and lipid composition in the major organelles.
e. none, all are true.
Answer:
D
Explanation:
A scientist discovers a new microscopic structure and hypothesizes that it is a living organism. Which of the following characteristics would support the contention that this "organism" may be alive?
a. It contains DNA.
b. It consists of a single cell.
c. It maintains a constant interval environment.
d. All of the above.
Answer:
The correct answer will be option-D.
Explanation:
Biologists have identified eight characteristic feature of a living organism which distinguishes the living organism from non-living organism.
The features are that organisms should contain: cells, heredity material, metabolism, reproduction, sensitivity, homeostasis, growth and development.
In the given question, when the scientist hypothesized that structure is living organism then it should show all the options provided as all of these features are shared by the living organism.
Thus, option-D is the correct answer.
In a playoff game between the State City Champions and the Anytown Victors, Sara initially bet against the State City Champions, who eventually won. After the game, she claimed she knew the Champions would be the winners. This is an example of a flaw in thinking called the _____ bias.
Answer:
This flaw of thinking is called the HINDSIGHT bias.
Explanation:
"We don't really know the result, but we think as though we do."
The Hindsight bias, creeping determinism, or knew-it-all-along phenomenon, is the assumption of an individual regarding an event that have already occurred as expected, as if he knew it even before the event took place. This leads to the person believing they have a high sense of certainty of what the outcome would really be, even before the culminating of the event. This usually results to overconfidence or overestimation in recalling the sequence of events before the predicted bias.
There are 3 levels of hindsight bias Memory distortion - unable to recall the previous judgment ("I said it would happen").Inevitability - the event must happen even with or without the circumstances (“It had to happen”).Foreseeability - that belief and confidence wherein results of the event were already anticipated, even way before the event culmination (“I knew it would happen”).3. What 20th century discovery has been instrumental to the field of genetic engineering by allowing researchers to cut and splice specific DNA fragments into microorganisms?
a) Small RNAs
b) Restriction enzymes
c) Ribozymes
d) The microbiome
Answer:
b) Restriction enzymes
Explanation:
Restriction enzymes are the endonucleases that recognize and cut the specific DNA sequence and breakdown the DNA into smaller fragments.
With the discovery of these enzymes, it became possible to cut the genome of microbes or any other organism at the specific site.
For example, the restriction sequence for the restriction enzyme EcoRI is 5' GAATTC 3' on one strand and it cuts between G and A of the sequence and between A and G on the complementary strand.
A student formulated a hypothesis that cotton will grow larger bolls (pods) if magnesium is added to the soil. The student has two experimental fields of cotton, one with magnesium and one without. Which data should be collected to support this hypothesis?
Answer:
The comparison of the size between groups.
Explanation:
This is like a quasi experimental design, where you need to compare the two groups after you apply the stimulus to the experimental group.
To do this comparison you need to collect the size measurement data, that's when you're gonna support your hypothesis or not. Why size data between groups? Simply because your hypothesis is about larger growing cotton bolls, and that refers to size.
In fruit flies, an autosomal mutation in the gene for wing veining results in cross veinless wings. This mutation is recessive. At another gene, an autosomal recessive mutation results in white eyes. Which of the following indicates the genotype of an individual heterozygous at both loci?
A. CV+CV W+ W
B. cv+cv w+w
C. v+v r+ r
D. V+V R+R
Answer:
B. cv+cv w+w
Explanation:
Fruit flies have a special nomenclature to write the genotype of individuals.
If the mutation is recessive, you have to write it with lowercase letter(s).If the mutation is dominant, you have to write it with capital letter(s).Wild-type alleles are indicated with a superscript plus (+).In this problem, both crossveinless (cv) and white (w) mutations are recessive.
For that reason, a heterozygous individual's genotype for both genes will be written as:
cv⁺ cv w⁺ wThe genotype of an individual fruit fly heterozygous at both loci for veinless wings and white eyes would be represented as 'cv+cv w+w'. This individual carries one dominant and one recessive allele for each trait, meaning the dominant traits of normal wing veining and normal eye color would be expressed.
Explanation:In genetics, the term heterozygous refers to an individual having two different alleles for a particular gene. In the case of fruit flies, the genotype of an individual heterozygous at both loci means carrying one dominant and one recessive allele for each mutation: one for the veinless wing characteristic and another for the white eyes characteristic.
The correct answer to the given question would therefore be B. cv+cv w+w. Here, 'cv+' and 'w+' denote the dominant alleles for the normal wing veining and eye color, respectively, while 'cv' and 'w' refer to the recessive alleles that lead to veinless wings and white eyes, respectively. Given that both are recessive traits, each needs a double dose of the respective mutated gene to express itself, so a heterozygous fly would not show either trait.
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The names of muscles often indicate the action of the muscle. What does the term levator mean?
A. The muscle flexes and rotates a region.
B. The muscle elevates and/or adducts a region.
C. The muscle functions as a synergist.
D. The muscle is a fixator and stabilizes a bone or joint.
Answer:
The right answer is B. The muscle elevates and/or adducts a region.
Explanation:
Levator muscles are the muscles use to raise any region of the body. Like levator anguli oris which elevates the corner of the mouth, levator ani which is made up of many muscle sheets of iliococcygeus, puboretalis, and pubococcygeus muscles and holds pelvic viscera in their place.
Levators costarum during breathing helps in raising the ribs, levator palpebrae superioris have function in raising the eyelids and there are so many levator muscles are present in different places in the body which helps to elevate and/or adducts a region.
Therefore, the right answer is B. The muscle elevates and/or adducts a region.
Two organisms live in the same geographical area, are very similar genetically, and can breed with each other successfully. Which of the following statements is correct?
a. These organisms have undergone natural selection.
b. These organisms are members of different populations.
c. These organisms are members of the same species.
d. These organisms have gone extinct.
Answer: Option C
Explanation:
When two genetically similar species can breed among each other in order to produce a fertile offspring then it is known as members of same species.
The offspring that is produced must be fertile in order to extend the members in the same species.
Two organism can breed because they are genetically similar and the similarity allows the organism produces a fertile offspring.
You hang a microscope slide from a submerged, L-shaped PVC pipe in lake water that is 2 feet deep. The slide hangs 6 inches below the surface of the water and remains there for eight weeks. When you remove it and bring it to your lab for observation, you see that algae, bacteria, and even some fungi have colonized the slide. You determine that you are looking at a(n)
Answer:
The correct answer is a biofilm.
Explanation:
A collection of one or more kinds of microbes, which can grow on various distinct surfaces is considered as a biofilm. The microbes, which produce biofilms comprise fungi, bacteria, and protists. One prime illustration of a biofilm is a dental plaque, that is, a slimy accumulation of bacteria, which develops on the surface of teeth.
Final answer:
The colonization of algae, bacteria, and fungi on the microscope slide that was submerged in lake water for eight weeks indicates the observation of a biofilm.
Explanation:
The colonization of algae, bacteria, and fungi on the microscope slide that was submerged 6 inches below the surface of the water in a lake for eight weeks indicates the observation of a biofilm. A biofilm forms when planktonic bacteria adhere to a surface and produce slime, resulting in the formation of a colony. In this case, the water's dissolved organic carbon (DOC) and larger particles contributed to the growth of biofilm and prevented algal blooms.
how do organisms carry out chemical activity of life?
A. through homeostasis
B. through asexual reproduction
C. by increasing metabolism
Answer:
I believe c
Explanation:
A guest called an operation and told the manager about getting sick after eating there.The guest complained of vomiting and diarrhea a few hours after eating the raw oysters.What pathogen probably caused the illness?
a) Norovirus
b) Shigella spp.
c) Salmonella Typhi
d) Enterohemorrhagic and shiga toxin-producing E.coli
Answer:
a) Norovirus
Explanation:
Norovirus also known as winter vomiting bug is a very contagious virus. It causes vomiting, diarrhea and stomach pain. It can spread from eating contaminated food or by person to person. Oysters and other shell fish are very common agents of norovirus outbreaks. When they are exposed to untreated human sewage they come in contact with the virus. They filter sea water via their bodies to obtain food but norovirus is able to cross their bodies and accumulates inside them. Oysters are typically at more risk of transmitting the disease because they are eaten raw. To reduce the risk of norovirus shellfish should be cooked at a temperature of 145 degrees Fahrenheit.
What are the two major factors determining the distribution of terrestrial biomes?temperature and light temperature and rainfall light and rainfall plants and animals temperature and plants
Answer:
Temperature and light
Explanation:
This two factors are determinants in terrestrial biomes, because the temperature is closely related to rainfall, to the formation of glaciers, to the migration of species. And the light is related from the use of these reay by the plant, through the greenhouse effect. This two make the biodiversity to be what it are
The table below shows the number of chromosome pairs for various
organisms
Organism
Number of
Chromosome Pairs
Hare
24
Hyena
20
Kangaroo
6
Meerkat
36
)
Which organism can produce the highest number of genetically different
gametes?
Answer:
The correct answer will be option- Meerkat with 36 chromosome pairs
Explanation:
Genetic diversity in organisms takes place by the process recombination which takes place during cell division through meiosis.
The process of meiosis takes place during the gamete formation in organisms. During prophase I of meiosis, the exchange of DNA between sister chromatids takes place mediated by the formation of the synapse between chromosomes.
If the number of chromosomes in an organism will be high then there will be more probability of the genetic recombination process in those organisms.
So the organism with a high number of chromosome pairs can have the maximum chances of genetic recombination and genetic diversity. Thus, the selected option is the correct answer.
What process is shown in the diagram below?
Answer:
my answer is the use of restriction enzymes.
Answer:
Use of restriction enzymes.
Explanation:
Restriction enzymes are also known as molecule scissors in the recombinant DNA technology. Two main types of restriction endonuclease are exonuclease and endonuclease.
The main function of the endonucleases is to cut the DNA fragments at the specific site. In the diagram, the restriction enzymes function has been shown. The restriction site of the enzyme has been specified and depicted in the picture.
Thus, the correct answer is option (C).
Question 7
A reaction between an acid and a base that produces a salt and water is a(n)_____ reaction.
A)neutralization
B)synthesis
C)decomposition
D)endpoint
Answer:
Neutralization
Explanation:
Neutralization, there is nothing much to add. Neutralization is the reaction of an acid and a base. A typical acid is HA and a typical base BOH the reaction is:
HA + BOH -> H2O + BA
H2O is water
BA is the salt
Answer:
A reaction between an acid and a base that produces a salt and water is a neutralization reaction. Hence the answer is option A.
Explanation:
A neutralization reaction is defined as when a chemical utilize the other chemical during the course of reaction. In this case the acid utilizes the base and the base neutralizes the acid. During the course of reaction the salt is formed and the salt is deposited in the base of the container.
Acid can turn blue litmus into red whereas a base can turn red litmus paper into blue. According to the pH value of acid is defined as whose value is is less than 7 and a base is defined as whose value is more than 7 up to 14.
A person’s work, social, and family environments can have a strong influence on eating and activity behaviors. When these factors are positive, they can help a person maintain a healthy weight. However, too many negative influences can contribute to obesity. Which of the following are not examples of societal influences that can contribute to obesity?
Select all that apply
a. food commercials during a popular television show
b. an individual's self-esteem
c. a person adopting American habits after moving from a different country
d. a person's resting metabolic rate
e. reasonable cost and availability of a wide variety of television, movie, and computer gaming options
Answer:
The correct answers are options b and d.
Explanation:
Obesity refers to a complex ailment that comprises an excessive concentration of body fat. It refers to a medical condition, which enhances the threat of other diseases and health issues like diabetes, heart disease, a certain type of cancers, and high blood pressure.
There are many causes why some individuals exhibit difficulty in preventing obesity. Generally, obesity results from a combination of social, environmental and inherited factors, apart from this it also depends upon one's personal diet and exercise choices.
Some of the risk factors for the development of the condition are family inheritance and influences, an unhealthy diet, and inactivity.
Some of the societal influences that can contribute to the condition is getting influenced by the food commercials displayed in between the television shows, adoption of unhealthy habits, and easier accessibility of movie, television, and computer games that enhances the sedentary lifestyle of an individual.
However, of the mentioned options, the self-esteem of an individual, and the resting metabolic rate of the individual do not contribute to obesity. Thus, the mentioned options are not examples of societal elements contributing to obesity.
what is fetch, definition???
Answer:
achieve when sold
Explanation:
When soft-centered chocolates are made, the enzyme invertase is used to convert sucrose into glucose and fructose. This causes the chocolate centers to become softer and sweeter.
Identify the substrate, enzyme, and product in the above reaction.
An in advance thanks to anyone who replies! :D
The substrate in the reaction is sucrose, the enzyme used is invertase and the product formed is glucose.
What is a substrate?A substance on which certain enzymes acts and forms product is referred to as a substrate.
In the given situation, the sucrose is converted into product called glucose by the action of enzyme invertase.
Thus, the substrate in the reaction is sucrose, the enzyme used is invertase and the product formed is glucose.
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The answers are: a) The enzyme should not be heated above 45°C to avoid denaturation. b) Invertase accelerates the conversion of sucrose into glucose and fructose by decreasing the activation energy of the hydrolysis reaction. c) Increasing the substrate concentration can diminish the impact of inhibitors on the enzyme's activity.
Using Invertase in Soft-Centred Chocolates:
Invertase is an enzyme crucial in the production of soft-centred chocolates as it converts sucrose into the smaller molecules glucose and fructose. This conversion makes the centres softer and sweeter.
A) Temperature Sensitivity of Invertase:
Invertase must not be heated to temperatures above 45°C because enzymes are proteins that can denature at high temperatures. Denaturation causes the enzyme to lose its structure and, consequently, its functional activity, meaning it would no longer catalyze the conversion of sucrose to glucose and fructose efficiently.
B) Mechanism of Action
Invertase increases the rate of conversion of sucrose into glucose and fructose by lowering the activation energy of the hydrolysis reaction. This enzyme binds to the sucrose molecule at its active site, facilitating the breaking of the glycosidic bond between glucose and fructose more efficiently than would occur in the absence of the enzyme.
C) Effect of an Inhibitor
The effect of an inhibitor on invertase may be reduced by increasing the concentration of the substrate (sucrose) because there will be more substrate molecules available to bind to the enzyme’s active sites.
This reduces the chances of the inhibitor molecules binding to the enzyme instead of the substrate, thereby allowing the enzyme to continue catalyzing the reaction.
Complete Question: -
When soft-centred chocolates are made, the enzyme invertase is used to convert sucrose into the smaller molecules glucode and fructose. This causes the centres of the chocolates to become softer and sweeter.
a) state why the invertase must not be heated to temperatures above 45°.
b) state how invertase increases the rate of conversion of sucrose into glucose and fructose.
c) Explain why the effect of an inhibitor on an enzyme may be reduced by increasing the concentration of the substrate
For the statements below indicate whether it is a hypothesis, theory, natural law or if it is not a scientific statement at all. Provide an explanation for your reasoning.
Statement 1: By increasing the amount of sun exposure the growth of a tomato plant will increase.
Statement 2: Energy cannot be created or destroyed
Statement 3: When newly industrialized parts of Britain became polluted in the nineteenth century, smoke killed lichens growing on trees and blackened their bark. Pale colored moths which had been well camouflaged before when they rested on tree trunks became very conspicuous and were easily found and eaten by birds. Rare dark moths, which had been conspicuous before, were now well camouflaged in the black background. Birds switched from eating mainly dark moths to pale moths. Over time, the most common moth color changed from pale to dark. Natural selection had caused a change in the British moth population.
Answer:
Statement 1: hypothesis
Statement 2: natural law
Statement 3: theory
Explanation:
1) An hypothesis is a proposed explanation for a phenomenon. It provides a suggested outcome. It needs to be tested through experimentation.
The statement says that an increase in sun exposure, increases the tomato plant growth, which is a suggested outcome and it can be tested.
2) Energy cannot be created or destroyed, is the first law of thermodynamics.
A scientific law is the description of an observed phenomenon. Without an explanation of the causes behind it.
3) A scientific theory is the explanation of a given phenomenon, based on a large body of empirical data.
This why after the pale and dark moths example, it says: Natural Selection had caused a change in the British moth population.
It is a theory that explains the phenomenon quoted.
What type of tissue has cells that are tightly packed
Answer:
The answer would be the epithelial tissue.
Explanation:
Epithelial tissue. The cells in epithelial tissue are tightly packed together with very little intercellular matrix. Because the tissues form coverings and linings, the cells have one free surface that is not in contact with other cells.
The "Bateman gradient" states that males have more variable reproductive success than do females, since males can mate with many females while females are limited by the number of eggs they produce. This explains why the male Idaho ground squirrel follows his mate everywhere. True or False
Answer:
False
Explanation:
The Given statement of False. As The "Bateman gradient" states that males have more variable reproductive success than do females, since males can mate with many females while females are limited by the number of eggs they produce. This is false statement. This does not explain why the male Idaho ground squirrel follows his mate everywhere.
What happens during RNA splicing? RNA polymerase adds nucleotides to an mRNA strand. Enzymes cut introns out of an mRNA strand. A cap and tail are added to an mRNA strand. Transfer RNA is removed from an mRNA strand.
Answer:
It makes the RNA strand shorter
Explanation:
It is to make the process easier and quicker
Answer:
B (Enzymes cut introns out of an mRNA strand)
Explanation:
When an RNA transcript is first made in an eukaryotic cell, it is considered a pre-mRNA. Eukaryotes undergo processing of the pre-mRNA strand immediately after transcription. The genes of an eukaryote are split up into parts that are expressed as RNA products and parts that are not. The parts that contains the actual coding regions and are expressed are called EXONS while the parts removed from in between the exons and referred to as "junk sequences" are called INTRONS.
Introns and exons alternate with each other along the length of the gene. Introns are usually considered the non-coding regions because they don't seem to code for any protein, hence they are removed before the mRNA product is finally ready for translation. This post- transcriptional process is called RNA SPLICING. RNA SPLICING can be likened to the process of removing the chaff (introns) from the wheat (exons). It is the removal of introns and joining of exons in eukaryotic mRNA.
Splicing is carried out by SPLICEOSOMES ( a protein and RNA complex), which removes introns from the genes in mRNA. They locate the ends of the INTRONS, cut them away from the EXONS, and join the ends of adjacent exons together. Once the entire gene is devoid of introns, the process of RNA splicing is complete.
It is worthy to note that, not only do the introns not carry information to build a protein, they actually have to be removed in order for the mRNA to encode a protein with the right sequence. If the spliceosome fails to remove an intron, an mRNA with extra "junk" in it will be made, and a wrong protein will get produced during translation.
After a period of rapid growth (log phase), bacterial growth rates will slow and enter the stationary phase. The number of viable cells no longer increases, but instead stays constant. In this activity you will indicate the statements that correctly describe what is happening during stationary phase. Reasons?
A. The number of cells that are dying is balanced by the number of new cells that are being formed.
B. Cells are not increasing in number because they have not yet adjusted to the nutrient availability in the new media.
C. Harmful waste products may be accumulating.
D. The cells are likely running out of nutrients.
Answer:
A. The number of cells that are dying is balanced by the number of new cells that are being formed.
C. Harmful waste products may be accumulating.
D. The cells are likely running out of nutrients.
Explanation:
During the stationary phase, the number of viable cells remains constant. This may be due to a balance between cell division and cell death wherein the total number of newly formed cells and the cells undergoing death are equal.
Nutrient limitation is one of the several factors that make the microbial cells to enter the stationary phase. Depletion of nutrients slows down the population growth.
Accumulation of toxic waste products as it occurs during the growth of anaerobic bacteria also adversely affects the population growth.
For example, the accumulation of lactic acid and other organic acids (by-products of anaerobic respiration) inhibits the growth of the population by making the medium acidic.
Identify the statement about digestion of DNA by restriction enzymes that is NOT true.
a. It generates restriction fragments.
b. It produces blunt ends. It produces sticky ends.
c. One strand of the DNA molecule is cut.
d. All of the answer choices are correct.
Answer:
c. One strand of the DNA molecule is cut.
Explanation:
Restriction enzymes or RE cut both strands of a DNA molecule, generating restriction fragments with sticky or blunt ends. These enzymes can cut in more than one place in the chain.
A RE creates 2 or more restriction fragments if it cuts in at least 1 place of a linear DNA nolecule or in 2 or more places of a circular DNA molecule.
Final answer:
The incorrect statement is option c, as restriction enzymes cut both strands of the DNA, either producing sticky ends with overhangs or blunt ends with no overhangs, facilitating the recombination of DNA fragments.
Explanation:
The statement about the digestion of DNA by restriction enzymes that is NOT true is option c: One strand of the DNA molecule is cut. Restriction enzymes, by nature, cut both strands of the DNA molecule. Some restriction enzymes make staggered cuts in both strands, producing "sticky ends" that have overhanging single-stranded DNA, while others produce a straight, or blunt, cut across both strands, leaving behind "blunt ends". Both mechanisms are designed to allow easier recombination of DNA fragments. For example, the enzyme BamHI cuts at specific recognition sites to produce sticky ends, and HaeIII cuts to produce blunt ends. The process enables the production of recombinant DNA by joining DNA fragments from different sources, which are cut with the same enzyme, thereby ensuring that the ends of the fragments can ligate.
A student is provided with a pure culture and asked to make a three-phase streak plate. The student takes a sample of the culture and streaks the first sector of the plate. What is the next step?
Answer:
The following step is to sterilize the wire loop, turn the plate 90 degrees, collect some organisms from the first area and continue to streak on the second area. Repeat for the third area.
Explanation:
The goal of three-phase streak is to obtain isolated colonies in the plate. To do this, the culture is diluted by spreading it through the entire plate.
In the first phase, one third of the plate is used to streak the initial inoculum in a zig-zag motion. As the wire spreads, the densitiy of organisms diminishes and colonies start to be further apart. Doing this only one time, is usually not enough to obtain isolated or separated colonies. So two more phases are used.
Before the second phase, the wire is sterilized, and colonies are collected by passing through the first area two or three times, so the inoculum now is much smaller than at the beginning. The organisms are spread in the second third of the plate, also in a zig-zag motion.
The same process is repeated in the third phase, by filling the remaining area of the plate.
By doing this, it is very probable that the initial culture is diluted enough to obtain single, isolated colonies in the plate which can then be grown separately in order to identify them.