A.P Bio Quiz

DNA molecular cloning is a type of experimental method that is used to bind together recombinant DNA molecules and aid replication of these molecules in host organisms. Which of the following is NOT a key step in the process of DNA molecular cloning?

Seal plasmid carrying targeted genes into host cell's genome using ligase.

Restriction Fragment Length Polymorphisms (RFLPs) result in differing length DNA fragments between samples due to varying length introns. Which of the following explains why RFLP analysis is such a useful tool in biotechnology today?

It can be used to accurately differentiate DNA samples between different sources, utilized in evolutionary analysis, forensics, paternity testing, and for finding genes linked to diseases.

In bacterial transformation, a scientist uses restriction enzymes EcoRI and HaeIII in a digest of a bacterial plasmid. The resulting DNA fragments are shown in the gel electrophoresis below. What is the total size of the plasmid?

24 kbp

A scientist examines the DNA taken from a leaf cell and the DNA taken from a root cell in a plant. Which of the following CORRECTLY predicts her observations?

She would observe that the DNA samples would show different DNA methylation patterns.

In a bacterial transformation experiment, a scientist aimed to insert the human insulin gene into E. coli bacteria using a plasmid. Which of the following BEST explains why the restriction enzyme used in this experiment must include recognition sites in the origin of replication in the plasmid?

Without the origin of replication, the plasmid will not replicate in bacteria and transformation efficiency will be low.

DNA replication proceeds in a particular direction with specific base pairing patterns. 3′ A - T - C - C - G 5′ Based on the sequence shown above, which of the following DNA strands is complementary to the strand shown?

5' T - A - G - G - C 3'

Which of the following BEST describes how the mRNA undergoes a series of modifications after transcription?

A GTP cap and a poly A tail are added to protect the mRNA as it leaves the nucleus.

Histone proteins have tails that protrude out from a nucleosome. These can be methylated, causing chromatin to pack more tightly together, or acetylated, promoting a loose chromatin structure. Which of the following could a researcher expect to find when examining the histones of inactivated X chromosomes?

A high amount of methylation.

A section of a sequence of coding mRNA reads "...AGG UUA CGC..." Which of the following mutations would have the greatest effect on altering the shape of the protein and why?

A mutation that eliminated the first G because it is a frameshift.

The image above represents an example of a generation of induced pluripotent stem cells. These stem cells are important in regenerative medicine as they are generated from adults and have the potential to replace damaged organs. Which of the following is the BEST explanation of how this image represents an example of genetic variation?

A viral vector containing stem cell genes is introduced to donor cells that harvest induced pluripotent cells.

Though a large percentage of our genes are considered to be non-protein coding, evidence suggests that a large amount of this DNA is used in a regulatory fashion in order to determine which protein-coding genes are expressed and which are not. It is likely that much of this non-protein coding DNA is transcribed into various types of RNA molecules with regulatory functioning. Which of the following accurately represents a post-transcriptional mechanism of gene regulation?

Alternative mRNA splicing.

All organisms have a series of events that can be thought of as safeguards or checkpoints that are involved in regulating and ensuring the proper expression of genes. This regulation can be categorized as either pre-transcriptional or post-transcriptional control. One such example of this regulation is through alternative splicing as depicted in the image below. Which of the following BEST explains the evolutionary advantage of alternative splicing?

Alternative splicing is a post-transcriptional regulatory mechanism that increases the efficiency of protein coding and expression. This has also allowed for a greater tolerance for minor errors in coding as a new protein isoform may be created, which can allow for the retention of the protein function with limited, if any, disruption.

Homeotic genes are responsible for the development of structures in an organism. A group of homeotic genes called Hox genes encode transcription factor proteins that express the phenotypic structure in the correct region. Based on the figure above, which of the following sets of Hox genes would be responsible for expressing legs near the eye region if a mutation were present?

Antp: Antennapedia.

Okazaki fragments make up the lagging strand of the replicated DNA strand. Forming as short chunks of replicated DNA with small spaces in between segments, Okazaki fragments rely on ligase to seal the sugar-phosphate backbone between strands. Which of the following statements accurately describes why Okazaki fragments exist in the lagging strand of DNA replication?

Because DNA is antiparallel and DNA polymerase can only read from 3' to 5' on the DNA strand, the lagging strand will be replicated in the opposite direction of the replication fork, creating the need to fill in the gap of open single-stranded DNA when the replication fork continues to open.

A maternal effects gene is a type of transcription factor located within a mother's genome that affects the expression of DNA in the fetus. Many of these maternal effects genes are considered to be embryonic lethals in that the observation of their caused characteristics are never seen because the fetus is not viable to the point of birth. One example of a maternal effects gene is bicoid. This gene is responsible for development along the anterior/posterior axis. When present in proper amounts in fruit flies (Drosophila melanogaster), a proper head develops at one end, while a caudal (tail) end develops at the other. Generally, the highest amount of bicoid proteins is found at the anterior end, while very few bicoid proteins are found at the caudal end. Mutant copies of bicoid can result in the production of offspring with heads at both ends or tails at both ends, both of which are embryonic lethals. Based upon the information above as well as knowledge of the general processes of gene regulation and cell differentiation, which of the following offers the BEST description of how the bicoid gene helps to differentiate the anterior end from the posterior end in fruit flies?

Bicoid produces proteins that act as cytoplasmic determinants, which are molecules that regulate gene expression in nearby cells.

Which of the following would NOT be an important tool for using restriction fragment length polymorphism (RFLP) analysis?

Cloning a gene.

p53 is a protein that functions as a transcription factor, acting as a promoter for genes that lead to cell death in cells with damaged DNA. Sometimes cells also produce a protein called Mdm2 that also bonds with p53, preventing its attachment to DNA. Which of the following is the MOST likely effect this would have?

Competitive inhibition by the Mdm2 could reduce p53 activity, resulting in an abnormal, cancerous cell.

The restriction enzyme, Eco RI, recognizes and cuts the sequence below. Based on the cut pattern, which of the following types of bonds are cleaved by the action of the enzyme?

Covalent bonds between the sugar and phosphate groups.

The diagram above shows the results of a bacterial transformation lab. "LB" is nutrient broth. "Kanamycin" is an antibiotic. Lastly, "+kan" is a plasmid containing antibiotic resistance genes. Which of the following statements is TRUE regarding crossing over AND bacterial transformation?

Crossing over occurs during Meiosis I, and bacterial transformation occurs only in prokaryotes.

Translation is one of the steps involved in using the information stored as DNA to make proteins. Which of the following does NOT occur during translation?

DNA information is copied into a mRNA molecule.

Scientists have been able to splice the eukaryotic gene for the production of human insulin into the genome of bacterial cells and induce those bacteria to express the gene and produce insulin. This suggests which of the following?

DNA is a universal molecular carrier of genetic information for all life on the planet.

Examine the diagram of the Hershey-Chase experiment above. Which of the following was illustrated in the experiment by Hershey and Chase?

DNA was the molecule of heredity.

DNA replication is an incredibly specific process that involves careful coordination of a number of key enzymes. Errors in replication are relatively common, yet particular enzymes are used to proofread in order to decrease the amount of errors present in a given strand. In some cases, a mutation might arise that leads to a mutated protein. If a mutation were to arise in the enzyme helicase, which of the following is the MOST likely effect that this would have on the replication of DNA in the cell?

DNA would be unable to replicate due to the lack of exposed base pairs for replication.

Replication of DNA is a semiconservative process. Which of the following BEST describes this characteristic of replication?

Each strand of the original, double-stranded DNA molecule serves as a template for a newly constructed, complementary strand.

Genetic variation is essential for the survival of a species. Changes in an environment can apply selective pressure on a population. Many individuals may perish due to those changes. Individuals with advantageous variations may have a better chance of surviving and passing down those genes. Thus, the species persists. For example, the monoculture of Cavendish bananas has greatly reduced their genetic diversity. A new strain of the Panama disease caused by a fungus could potentially decimate the Cavendish population and the world's banana supply. Which of the following statements is TRUE regarding a mechanism for increasing genetic variation in BOTH eukaryotes and prokaryotes?

Errors during DNA replication can alter the phenotype of organisms.

Which of the following provides the BEST explanation for why undifferentiated stem cells injected into liver tissue samples then undergo differentiation and become functional liver cells?

Fully differentiated cells produce and secrete chemicals that can affect gene expression in neighboring cells.

Which of the following would NOT be a valid reason to use PCR?

Help in transferring DNA from a plasmid containing GFP into E. coli.

Sickle cell anemia is caused by the mutation of a single base pair in the gene for hemoglobin. This mutation results in hemoglobin molecules that form long chains in low-oxygen settings and stretch the blood cells into their characteristic sickle shape. Which of the following would result if a different base pair in the sickle cell hemoglobin gene were to become mutated?

It is impossible to predict what the effect would be without knowing more about the mutation.

Which of the following is primarily responsible for the rapid evolution of HIV?

Lack of proofreading when copying nucleic acids.

The two strands that make up a single molecule of DNA run antiparallel to one another. DNA synthesis only proceeds in the 5' to 3' direction; this means that one strand undergoes continuous construction (the leading strand), and the other creates fragments that have to be joined together after synthesis (the lagging strand). Which of the following enzymes is directly responsible for joining together the fragments of the DNA lagging strand?

Ligase

A fictional lizard population has a gene called Fire1. The dominant allele of this gene allows the lizard to produce a combustion reaction from glands in the back of their throat. A second gene, Fire2, codes for a protein that suppresses the expression of the Fire1 gene. The lizard population is not fire-breathing, but genetic analysis reveals that a majority of the lizards have at least one copy of the dominant Fire1 allele. Which of the following would be expected if a mutagen that targets the Fire2 gene was released into the lizard's environment?

Phenotypic variation will increase as some lizards will express the fire breathing trait.

Which of the following describes the correct statement regarding the bonding arrangement in the Watson-Crick model of DNA?

Phosphodiester bonds link to deoxyribose, forming the backbone of DNA.

Human Immunodeficiency Virus (HIV) is a retrovirus that causes Acquired Immune Deficiency Syndrome (AIDS). HIV infection causes a progressive failure of the immune system, causing cancers and various infections to overtake the patient. HIV is present as both free virus particles and a virus within infected immune cells and is transmitted via blood products (contaminated needles, unscreened blood), mother to child (pregnancy, labor, nursing) and unprotected sex. The life cycle​ of a retrovirus is illustrated below. Which of the following enzymes is needed for the virus to proceed from Step 4 to Step 5?

Reverse transcriptase.

Clustered regularly interspaced short palindromic repeats (CRiSPR) are found in prokaryotes and are used in a rudimentary immune response system by cutting DNA of phages and plasmids to prevent damage to the prokaryote. CRiSPR is associated with other proteins, such as cas9, to create a CRiSPR-associated complex (image below). These complexes allow for excision and insertion of genes along the length of the genome. Which of the following MOST accurately demonstrates an application of this system to biotechnology?

Since the CRiSPR-cas9 complex can splice DNA at specific sequences, the system can be artificially programmed to recognize specific sequences in DNA, allowing scientists to remove and insert genes of interest. An example of this use would be to modify mosquitoes to no longer transmit Zika.

A scientist uses the process of cell fractionation to isolate and collect in a test tube a sample of ribosomes from a eukaryotic cell. The scientist adds mRNA transcripts to the test tube along with all tRNA molecules and amino acids needed for protein synthesis, with the exception of the amino acid methionine and its associated tRNA molecule. After allowing the sample to sit for several minutes, which of the following would the scientist expect to find in the test tube?

Small ribosomal subunits associated with mRNA transcripts.

Which of the following statements BEST explains the sequential relationship between cellular structure and function?

Structure precedes cellular function and is determined by intrinsic and extrinsic regulation factors.

Prokaryotes are the perfect organism to begin to understand the mechanisms of gene expression and control. They are not only useful for understanding the interdependence of chemical signals in pathways, but they are also useful research tools. Many microbiologists will use prokaryotes and their operons to study the efficiency of transformation. Below is an example of an operon used to determine if the gene has been successfully integrated into a bacterial plasmid. Based on this information and the diagram, which of the following statements BEST describes the purpose of the amp (ampicillin) gene?

The amp gene will only be expressed if the plasmid is successfully transformed. Therefore, when grown on an ampicillin-containing medium, only those organisms that have successfully transformed the plasmid will survive.

A substitution mutation occurs in a gene coding for an enzyme. Which of the following choices is the MOST unlikely result?

The mutation produces a codon that codes for an amino acid with different chemical properties than the original. The enzyme now catalyzes a different reaction than the original.

Homeotic genes were first discovered in Drosophila fruit flies. They are genes that control the development and differentiation of tissues and organs in embryos. These genes are highly conserved in evolution. Alteration of these genes results in alterations in the ​development of limbs and tissues and is often so catastrophic that offspring does not survive. Which of the following BEST describes the role of homeotic genes?

These are genes that direct the development of tissues and organs in the embryo.

Humans must be able to digest the variety of macromolecules that is consumed. The stomach is capable of producing a protease, pepsin, to digest proteins. The small intestine produces sucrase, lactase, and maltase to digest carbohydrates. The pancreas produces lipases and another protease, called trypsin, to digest lipids and proteins, respectively. Which of the following statements is TRUE regarding these organs in an individual?

These tissue-specific proteins are the result of differential gene expression.

DNA replication is essential to the identical recreation of DNA into daughter cells. A number of key enzymes are necessary to complete the process of replication. Each enzyme has a unique role in the process, and the order of these enzymes is important to the successful replication of DNA. Which of the following statements provides the correct order of enzymes used in DNA replication from first to last?

Topoisomerase, Helicase, RNA Polymerase, DNA Polymerase, Ligase.

A particular polypeptide contains a consecutive sequence of the following hydrophobic amino acids: Glycine-Alanine-Valine-Proline-Isoleucine. Which of the following indicates where would you expect the region of the polypeptide to be located once the final protein was assembled in a cell?

Toward the inside of the folded protein, away from the cytoplasm.

The image shows a molecule of tRNA. Which of the following is the anticodon for this molecule?

UAC.

Which of the following is the function of the process shown which occurs during eukaryotic protein synthesis?

Unnecessary segments of the mRNA transcript are being removed prior to the start of translation.

HIV is a retrovirus. Which of the following BEST describes the flow of genetic information from viral transmission to the production of viral protein?

Viral RNA → Viral DNA → Host DNA → Host RNA → Protein.

Prokaryotes use operons to control gene expression. One specific operon is the lac operon. In this mechanism, the presence of cAMP (cyclic AMP) is used to control the expression of the gene within the operon. Use the image below to answer the question regarding the role of cAMP in lac operon expression. Which of the following statements BEST describes the role of cAMP in the expression of the lac operon?

When cAMP is present, the expression of the lac operon is the highest. This indicates that lactose is present as a food source and glucose is either absent or in very low concentration.

Scientists applied a treatment of nucleotide RNA fragments to Drosophila eggs that were complementary to bicoid mRNA. The fragments bonded with the bicoid mRNA molecules and blocked them from being transcribed. The resulting larva had bodies with no anterior parts but rather with posterior parts at both ends. The results of this experiment suggest that the protein products of the bicoid gene

are needed for the successful formation of head structures during development.

Water and light will cause gibberellic acid ( G A 1 GA1) to be released from storage within a plant seed. A chain of events results in the production of amylase, which is used to hydrolyze starch. Which of the following BEST explains how the amylase gene is regulated?

cGMP helps RNA polymerase bind onto the TATA box.

A scientist studying transcription in bacteria discovers a nonsense mutation in the regulatory gene of a repressible operon. The resulting protein products of the gene are non-functional. In the bacteria with this mutation, the scientist observes

continuous transcription of the operon associated with the regulatory gene.

The Human Immunodeficiency Virus, HIV, is a retrovirus that contains RNA as the genetic material. Scientists believe that the chimpanzee version of the immunodeficiency virus (called Simian Immunodeficiency Virus or SIV) was the original source of HIV infection in humans. It is theorized that SIV was transmitted to humans and mutated into HIV when humans in Africa hunted chimpanzees for meat and exposed themselves to the infected blood. The mutation rate in retroviruses, including SIV and HIV, is much higher than it is among DNA viruses. The MOST likely explanation for this is that

retroviruses like HIV lack replication error-checking mechanisms when copying DNA from RNA, and thus have higher rates of mutation.

Which of the following types of RNA or processes involving RNA is mismatched with its function?

tRNA molecules carry specific nucleotides to the mRNA and ribosomes during protein synthesis.

All somatic cells have the same genes necessary for normal development. However, the expression of these genes is different for each cell. This is because the genes NOT needed are

turned off or repressed.

The process of polymerase chain reaction MOST closely mirrors that of which of the following?

Replication.

Arctic foxes observed in their natural wild habitats develop white coats in the winter months. In the summer months, when they shed their winter coats the white fur is replaced by dark fur. Captive arctic foxes kept in zoos located at more southerly latitudes tend not to develop white "winter" coats unless their zoo habitats are cooled to mimic arctic temperatures. Which of the following is the MOST likely cause for the change in coat color observed in the wild fox populations?

Repression of the transcription of genes for pigment production brought on by colder environmental temperatures.

The figure below illustrates gene expression in prokaryotic and eukaryotic cells: Human insulin, a protein hormone that controls blood sugar levels, and many other eukaryotic proteins can be mass-produced by inserting eukaryotic genes into bacteria. If an unaltered gene for human insulin was inserted into the DNA of a bacteria cell, how would expression of the insulin gene be affected?

The insulin protein produced in the prokaryotic cell would be non-functional in humans because it would contain extra amino acids due to a lack of mRNA processing in prokaryotic cells.

A section of DNA appears as shown below. When replication occurs, this molecule is being unzipped in from left to right. Which of the following will be the leading strand, and why?

The top strand, because DNA polymerase replicates the template strand in a continuous 5' ⟶ 3' direction.

A circular plasmid of 24.0 kB 24.0 kB is digested with the restriction enzymes Hae III and EcoRI, then run on an agarose gel alongside a sizing ladder (right lane). Observe the results of a restriction digest of on this image of the gel electrophoresis. Which of the following conclusions can be drawn from the data?

There is one restriction site for EcoRI and two sites for Hae III.

Throughout the history of life, one of the driving factors of genetic diversity (regardless of whether or not the organisms are sexual or asexual reproducers) is mutation. Mutation can be defined as the spontaneous change in DNA. There have been numerous factors that have been investigated as carcinogens, or substances that increase the likelihood of mutation. Additionally, several different types of mutations have been identified. Of those identified, one of three possible effects may be conferred to the organism. One of these effects is inherently negative in that the organism's phenotype may be modified to lower its fitness in its respective environment. A second effect is inherently positive in that the organism's phenotype may be modified to increase its fitness in its respective environment. The third effect is inherently neutral in that the organism's phenotype remains unchanged. Which of the following describes a situation that is the LEAST likely to lower an organism's fitness in its environment?

A substitution mutation exchanging the third DNA nucleotide of the codon TTC, which becomes TTT.

In a typical bacterial operon, which of the following describes where an operator is located to prevent transcription?

Between the gene and the region of the promoter where RNA polymerase attaches.

Which of the following particular characteristics of DNA replication causes the leading strand to be constructed more quickly than the lagging strand?

During replication, DNA can only be built in a 5' to 3' direction.

The template strand of DNA reads 3' TTCGGGTAGAAA 5'. A mutation occurs between the second and third base where an extra cytosine is added. Which of the following would be the resulting amino acids that would be translated from the gene?

Lysine-Alanine-Histidine-Leucine.

Differentiation results in the presence of cell types that have clear-cut identities, such as muscle cells, nerve cells, and skin cells. Which of the following is always involved in the process of cell differentiation?

Production of tissue-specific proteins.

During the process of cell division, it is necessary to make a duplicate copy of DNA for any new cells produced. First, the template strand of DNA is unwound by breaking the hydrogen bonds between the complementary strands. Next an RNA primer acts as an anchor for the new DNA strand to form. Last, matching nucleotides are connected to the growing DNA chain and gaps between DNA fragments are sealed together. All of these complex processes require enzymes in order to progress. All of the following enzymes are necessary for successful DNA replication EXCEPT

RNA polymerase

Homeotic genes (also referred to as Hox genes) are found in all animals. Unlike many protein-coding genes, Hox genes govern positional information along the developmental axis. It is the presence of these genes that allows bilaterally symmetrical animals to exhibit such symmetry by developing parts and appendages on both sides of the central body axis. In an experiment, a set of Hox genes governing the positional information of tail placement in a lizard was transplanted into a developing mouse embryo that had its normal caudal hox gene removed. Upon development, the mouse grew a tail that was normal and in the precise location that it should be. Which of the following is the BEST explanation for why a transplanted Hox gene was functional in this mouse?

Since all animals share a common ancestor, Hox genes function in a similar way from organism to organism. Because Hox genes contain only the information for where a body part should develop, the transplanted gene functioned in the mouse the same way that it would have in the lizard.

Which of the following describes the process seen in the image above?

The enhancer region is upstream from the binding site of RNA polymerase, which allows transcription factors to bind and initiate transcription.

A scientist is trying to determine the earliest point at which cell differentiation begins in the development of an earthworm. She should look for evidence of which of the following?

The presence of mRNA transcripts used for the production of tissue-specific proteins.

Which of the following is NOT a key step in the process of translation?

The sequence of nucleotides on the tRNA is read in triplets called codons.

Human Immunodeficiency Virus (HIV) is a retrovirus that causes Acquired Immune Deficiency Syndrome (AIDS). HIV infection causes a progressive failure of the immune system, causing cancers and various infections to overtake the patient. HIV is present as both free virus particles and a virus within infected immune cells and is transmitted via blood products (contaminated needles, unscreened blood), mother to child (pregnancy, labor, nursing) and unprotected sex. The life cycle​ of a retrovirus is illustrated below. Which of the following is needed for Step 2 to occur?

Glycoproteins on the virus coat bind to a complementary receptor on the host cell.

Myoglobin and hemoglobin are both protein molecules found in mammals that use heme groups to bind oxygen. Hemoglobin is found in red blood cells, while myoglobin is found in muscle cells. Which of the following BEST explains why mammals use two different oxygen binding protein molecules rather than just one?

Myoglobin and hemoglobin have different binding affinities for oxygen, so one can easily transfer oxygen to the other.

One of the major advantages of transforming bacteria with a plasmid that contains DNA of interest is to amplify the DNA. Which of the following laboratory techniques can be used to achieve the same result?

Polymerase chain reaction.

Fluorescent genes from a jellyfish can be inserted into bacteria with minor modifications, resulting in bacteria that can produce green fluorescent protein. Which of the following BEST explains why this is possible?

Prokaryotes and eukaryotes use the same codons for translation.

There is great genetic variation among types of viruses, and every species on Earth has its own unique category of viruses that are able to infect it. Furthermore, within a single species, viruses exhibit specificity for unique cell types. For example, Human Immunodeficiency Virus (HIV) infects T-helper immune cells, and Human Papilloma Virus (HPV) primarily infects the squamous epithelial cells that line the outside (skin) and inside of body cavities. The image below illustrates the basic structure of an animal virus: Which of the following BEST explains the specificity of viral infection?

The binding between viral surface proteins and membrane receptors on the host cell is limited to a specific membrane protein(s) on the host cell.

Vibrio cholerae, or simply cholera, has two forms. The first form is a harmless bacterium, while the second causes the deadly disease known as cholera, as seen in the image below. Cholera is a waterborne illness that infects the intestines, leading to severe diarrhea and vomiting. The severe water loss leads to death within hours if left untreated. Scientists were not sure how the harmless bacteria become harmful until recently. It was discovered that a lysogenic bacteriophage was responsible for the transformation. Which of the following explanations BEST explains why the virus had to be lysogenic and not lytic in order to cause the conversion of the cholera bacterium?

The lysogenic cycle leads to the integration of the viral prophage into the host DNA, allowing for the expression of new characteristics. The lytic cycle does not lead to the integration of the viral DNA into the host DNA.

A mixture of DNA fragments, such as those made by restriction enzyme digestion, can be resolved by gel electrophoresis. Loading DNA sample into wells at the top of the gel (see figure) will migrate through the gel in response to an electrical field. Which of the following components of the DNA macromolecule is responsible for its migration toward the positive terminal?

The phosphate group.

Fetal hemoglobin is the main oxygen transport protein in the human fetus, and it has a higher affinity for oxygen than the adult form of hemoglobin. This phenomenon is illustrated in the curve below: Both fetal and adult hemoglobin are quaternary proteins composed of four protein subunits. However, adult hemoglobin is composed of two α α (alpha) and two β β (beta) subunits, while fetal hemoglobin is composed of two α α (alpha) subunits and two γ γ (gamma) subunits. In humans, the gene that codes for the alpha subunit is on chromosome 16, and the genes for both the gamma subunit and the beta subunit are on different loci on chromosome 11. Fetal hemoglobin is replaced by adult hemoglobin by the time a newborn is about six months old. The best explanation for this is that

feedback mechanisms from the environment gradually silence the expression of γ γ (gamma) subunits of the hemoglobin protein and activate the expression of the gene coding for the β (beta) subunits.

The red viscacha rat has almost twice as many chromosomes as one of its closest relatives, the mountain viscacha rat. Which of the following mechanisms MOST likely resulted in the evolution of the red viscacha rat?

Errors in meiosis.

The contrast in the development and social behavior of the western honey bee, Apis mellifera, has been shown to depend on whether bee larvae are fed royal jelly or not. Those larvae fed jelly will accelerate growth and become queens; all others are destined to become drones. The drastically different developmental outcomes occur despite equivalent genomes, suggesting an epigenetic mechanism. Which of the following choices would be a feasible mechanism to investigate?

Methylation of histone proteins or genomic DNA, resulting in the silencing of genes.

Epigenetics is the study of how external environments affect gene expression, leading to changes in genotypes and phenotypes without a change in the underlying DNA sequence. Two common epigenetic mechanisms are DNA methylation and histone acetylation, both of which affect the packaging of DNA around histone proteins, as illustrated in Figure 1 below. Honey bee populations are a classic example of epigenetic phenomena because genetically—identical females develop into two significantly different castes: worker bees and queen bees. All female bees are diploid, but there are major morphological, physiological and behavioral differences between queen bees and worker bees. Queen bees are the only bees in the colony that can reproduce, and worker bees are sterile and responsible for feeding and maintaining the colony. Among the worker caste, there are two subcastes, which are nurses and foragers. The subcaste that a worker bee belongs to depends on its age, with all workers starting out as nurse bees that feed the larvae, clean the colony, and tend to the queen. As they get older, worker bees gradually shift to exclusively foraging duties like obtaining pollen and nectar resources from the environment and bringing it back to the hive. Which of the following is the MOST plausible explanation for the shift in worker bees' duties during their lifetime?

The DNA methylation pattern between nurses and foragers is different. DNA methylation increases in worker bees as they age, particularly in coding regions responsible for caretaking and housekeeping duties.

A child is born with albinism, an inability to produce or deposit the pigment protein, melanin, in skin cells, as well as other pigment-containing​ cells of the body. His parents do not display the trait of albinism. Which of the following explains how this is possible?

The parents each have one normal DNA allele and one that codes for albinism. The parents produce enough normal melanin protein to allow normal skin color, but the child cannot.

DNA isolated from a yeast cell was digested with restriction enzymes X and Y. The preparations were then electrophoresed on agarose gels producing the DNA fragment patterns shown in the figure. For the purpose of estimating fragment length, sizing markers were run simultaneously (lane 1). Other preps were: uncut DNA (lane 2), enzyme X-treated DNA (lane 3), enzyme-Y treated DNA (lane 4), DNA treated with enzymes X and Y simultaneously (lane 5). Based on the fragment patterns of the panel of digests, which of the following is the MOST likely restriction map?

Only straight lines X Y Y

Rosalind Franklin produced an X-ray image that helped Watson and Crick determine the width of a DNA molecule. Which of the following BEST explains what this information helped them realize?

Bonding between a purine and pyrimidine would be consistent with this width of a DNA helix since each rung has a three-ring molecular dimension.

The diagram above shows the process of transduction. "A" represents Cell 1, "B" represents Cell 2, and "a" represents Cell 1's DNA. Bacteriophage components are represented by the blue color. Which of the following statements is TRUE regarding transduction?

Cell B incorporated some of Cell A's DNA into its genome.

The Arctic cod is a species of fish found living in waters that reach below freezing temperatures. The fish are able to survive in subfreezing waters without their own cells freezing because they can produce an antifreeze protein that prevents the formation of ice crystals in the cytoplasm. The DNA sequence that codes for the antifreeze protein is right next to the DNA sequence that codes for a digestive protein. A small intron sequence separates the two. Based on this information, which of the following is MOST likely true?

The antifreeze sequence originated from the duplication of the existing DNA sequence for the digestive protein.

Chicken pox and shingles are skin infections caused by the Varicella Zoster Virus (VZV). While chicken pox occurs most commonly in children and is characterized by red itchy blisters, shingles occurs only in people who have been previously infected with chicken pox and most commonly in adults over 50. Shingles can cause very painful lesions of the skin, eyes and mucous membranes, and the duration may last for more than one month. Which of the following statements BEST explains why some adults develop shingles after they had chicken pox?

Varicella Zoster Virus (VZV) is able to switch from its latent lysogenic cycle to an active lytic cycle, reactivating after remaining dormant for many years.

Maternal effects genes are components of a mother organism's genome that act to methylate offspring DNA at various points to alter phenotypic expression. This type of gene regulation is not achieved by altering the offspring's DNA but rather by manipulating how the offspring's DNA is expressed. These maternal effects have been shown to be important in governing phenotypic plasticity as well as adaptive responses to environmental pressures. An example of an environmental pressure and the maternal effect that it triggers is prenatal hyperglycemia (when a pregnant mother has chronic high blood sugar) and obesity-related disease in her offspring. Evidence suggests that the obesity-related diseases are the result of an imbalance of leptin (a hormone associated with feeling full and satiated). Which of the following is the BEST explanation as to why prenatal hyperglycemia triggers these effects in offspring?

Prenatal hyperglycemia triggers changes to offspring leptin production in an inversely proportionate fashion.

A particular type of leukemia has been linked to a reciprocal translocation between chromosome 9 and chromosome 22. The shortened version of chromosome 22 is highly recognizable. Which of the following would be the BEST method to identify the presence of this mutation?

Karyotype.

Which of the following statements is NOT true regarding plasmids?

Plasmids are small, extra-chromosomal DNA molecules found only in bacteria.

PCR is a technique used to amplify a certain segment of DNA, potentially creating millions of copies. Which of the following describes a key step in performing PCR?

Addition of Taq polymerase to replicate the DNA.

Meselson and Stahl grew bacteria in the presence of a heavy isotope of nitrogen ( 14 N 14N). The DNA was then transferred to a growth medium containing nucleotides with a lighter isotope of nitrogen ( 12 N 12N) which then proceeded to replicate. The DNA was centrifuged to separate it by weight forming bands. After one round of DNA replication, there was one band in the middle of the centrifuge tube. After two rounds of DNA replication in the lighter nitrogen, two separate bands of DNA could be seen. This demonstrated that replication is semi-conservative. Which of the following BEST explains why these results support this idea?

After two rounds of replication, only two of the four daughter DNA molecules still contained the heavy nitrogen.

One can use DNA transformation as a laboratory method to study regulation of gene expression. One such system frequently used in high school biology is the genetically engineered plasmid, pGLO, which incorporates parts of the arabinose operon to drive the expression of green fluorescent protein (GFP). In the absence of arabinose, the regulatory protein ara C will bind to the operator region (O) of the *ara *operon and prevent transcription of the downstream genes, ara B, A and D. When present, arabinose will bind to ara C, changing its role to one that facilitates transcription and expression of the aforementioned genes, leading to the expression of proteins involved in the digestion of arabinose. In the case of the pGLO plasmid, the GFP gene has been swapped in for ara B, A and D positioned behind the promoter that drives the transcription of ara B, A and D. A β β-lactamase gene (bla) is included for antibiotic selection. The U-turn arrows on the ends indicate the circular nature of the plasmid. If one were interested in driving the expression of insulin under the control of arabinose exposure, in which of the following regions would the insulin gene be placed?

GFP

A gel electrophoresis was run to show the fragments produced by restriction digests with different restriction enzymes. The MWR lane indicates the molecular weight ruler. Which of the following constructs a restriction map of the double digest of the plasmid?

L to R Eco RI, 12, Hae III, 8, Hae III, 4

A single strand sequence of DNA reads, "5' ...GCC ATG ACT... 3". Which of the following amino acids would be coded with the enzyme RNA polymerase by this section?

Serine-histidine-glycine.

Biotechnology is a rapidly expanding and advancing field that includes many different techniques that edit, modify, and analyze genetic information. Removing abnormal bone marrow cells from a patient, treating those cells with specially modified viruses to insert a new, normal gene, and then putting the modified bone marrow cells back in the patient's body is an example of

genetic transplantation.

Which of the following gene mutations is LEAST likely to have a harmful effect on the resulting protein?

Which of the following gene mutations is LEAST likely to have a harmful effect on the resulting protein?

An operon is a cluster of regulated genes in prokaryotes, and it includes structural genes (coding for enzymes), regulatory genes (coding for activator or repressor proteins) and regulatory sites (promoters and operators). The lac operon is a classic example of gene regulation in prokaryotes, and its structural genes produce enzymes that metabolize the sugar lactose. Like all bacterial operons, the lac operon is able to produce multiple proteins from one mRNA transcript. The figure below illustrates the lac operon when it is "off" (top) and when it is "on" (bottom). Which of the following statements BEST describes the regulatory mechanism of the lac operon?

1 = RNA polymerase 2 = repressor protein 3 = promoter 4 = operator 5 = inducer molecule (lactose) The lac operon remains off unless an inducer molecule binds to and removes the repressor protein from the operator allowing RNA polymerase to transcribe genes 6, 7, 8. This mechanism of gene regulation represents negative control because an active repressor blocks the expression of genes 6, 7, 8, and an inducer molecule is required to activate gene expression.

Cystic fibrosis (CF) is a genetic disorder that is caused by a mutation in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The CFTR protein is anchored to the membrane of cells in the sweat glands, lungs, and other exocrine glands, and it allows chloride ions to move out of cells which, in turn, causes water to leave the cells via osmosis. When the CFTR protein is working correctly, as shown in Panel 1 below, chloride ions and water flow freely in and out of cells. However, when the CFTR protein is malfunctioning as in Panel 2, chloride ions and water cannot flow out of the cell. This causes Cystic Fibrosis, characterized by the accumulation of thick mucus outside of cells, particularly the tissue that lines the respiratory tract. The most common mutation in the CFTR gene is called delta F508, which is a deletion of three nucleotides resulting in the loss of the amino acid phenylalanine on the CFTR protein. An individual must inherit the mutant gene on chromosome 7 from each parent in order to have the disorder, which results in an abnormal CFTR protein. The mutant CFTR protein results in the accumulation of chloride ions and water inside cells and the production of mucus that is abnormally thick and sticky. The abnormal mucus obstructs the airways and other glands, leading to impaired function of the lungs, pancreas, liver, kidneys, and intestine. Children with cystic fibrosis are unable to get enough nutrients from food because of the lack of enzymes to help absorb fats and proteins. Males with the disease are born sterile. Which of the following statements BEST explains the inheritance pattern and phenotypic variations of cystic fibrosis?

Cystic fibrosis an autosomal recessive condition in which a single gene has many phenotypic effects on the individual.

In 1944, the research team of Avery, McCarty, and MacLeod purified an extract from virulent pneumococcal bacteria. This extract was treated with various enzymes that either degraded proteins, RNA, lipids, or carbohydrates. This mixture was combined with nonvirulent bacteria that normally formed rough colonies. After mixing, the nonvirulent bacteria then became able to form smooth colonies. This change from rough to smooth colonies did not occur when, instead, the DNA was broken down by enzymes. Which of the following major concepts of genetics was illustrated in the experiment by Avery, McLeod, and McCarty?

DNA is the transforming factor.

Escherichia coli bacteria generally prefer to digest glucose sugars. As glucose is a monosaccharide, it is easily broken down by the enzymes found in E. coli. In the event that glucose is not present in the growth medium, many E. coli turn to other food sources. Under normal conditions (when glucose is plentiful), E. coli restrict the use of resources by suppressing the genes that produce enzymes to digest other sugars. Of the known sugars digestible to E. coli, lactose (a disaccharide) can be digested in the absence of glucose. In order for E. coli to digest lactose, however, a set of genes coding for the production of the Beta-galactosidase, permease, and transacetylase must first be transcribed. When glucose is present in the growth medium, a repressor protein is normally bound to a region of the promoter called the operator. While the operator is blocked, transcription factors and RNA polymerase are unable to bind, in essence, blocking the transcription of the enzymes needed to digest lactose. If glucose is not present in the growth medium when lactose is present, an isomer of lactose (called allolactose) binds to a region of the repressor protein and inactivates it. The inactivated repressor detaches from the operator and frees up the site for transcription factors and RNA polymerase to bind, thus transcribing the mRNA to produce the necessary enzymes to digest lactose. If and when all of the lactose in the growth medium is used up (including the allolactose bound to the repressor protein), the repressor protein reactivates and re-attaches to the operator, thus shutting off the production of lactose-digesting enzymes. Which of the following is the MOST complete explanation for why E. coli use a lac operon rather than continuously transcribing the genes to produce the enzymes needed for lactose digestion?

E. coli mutants with an ability to digest lactose would have a selective advantage in instances when glucose was scarce. However, constantly transcribing the genes to digest lactose would have been too metabolically costly. Therefore, the pathway selected for was a part-time lactose digestion pathway.

There are two strains of bacteria: one is rough in appearance, and the other appears smooth because it is capable of producing a capsule. Griffith injected mice in several experiments, and the results are shown in the diagram above. When the bacteria were examined from the last part of the experiment, it was found that the rough strain bacteria could produce the capsule that the smooth strain bacteria had. Which of the following statements is TRUE regarding the process that made the rough strain virulent?

Genetic variation increased as a result of the rough strain obtaining DNA from the environment.

Cystic fibrosis (CF) is an autosomal recessive disorder that is caused by a mutation in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The CFTR protein is anchored to the membrane of cells in the sweat glands, lungs, and other exocrine glands, and it allows chloride ions to move out of cells which, in turn, causes water to leave the cells via osmosis. The most common mutation in the CFTR gene is called delta F508, which is a deletion of three nucleotides resulting in the loss of the amino acid phenylalanine on the CFTR protein. This abnormal CFTR protein breaks down shortly after it is made in the endoplasmic reticulum, so it never reaches the cell membrane. The result is the accumulation of chloride ions and water inside cells and the production of mucus that is abnormally thick and sticky. The abnormal mucus obstructs the airways and other glands, leading to impaired function of​ the lungs, pancreas, liver, kidneys, and intestine. The diagram below shows a partial gene sequence for the normal cystic fibrosis transmembrane conductance regulator (CFTR) protein: Normal Nucleotide Sequence (sense strand, which is the same as the mRNA sequence): 5'-ATC-ATC-TTT-GGT-GTT-3' The three-base deletion that causes cystic fibrosis is shown in the partial gene sequence of nucleotide bases below: Mutant Nucleotide Sequence (sense strand, which is the same as the mRNA sequence): 5'-ATC-ATT-GGT-GTT-3' The chart below shows the amino acids produced by each possible combination of three RNA bases. Using the chart, which of the following identifies the amino acid sequences in the normal and mutant nucleotide sequences provided above?

Normal: Ile-Ile-Phe-Gly-Val Mutant: Ile-Ile-Gly-Val

Barbara McClintock was awarded the Nobel Prize for her discovery of transposons in corn. The insertion sequence contains one gene for the transposase enzyme and two inverted repeats. The transposon has been found to move from one location to another. Which of the following is the BEST explanation for the process of transposition?

Specific segments of DNA are excised and placed back into DNA molecules at another location.

Which of the following would be the three-base sequence on the DNA used to complement the RNA codon that matches the anticodon shown in the figure above?

TAC.

Certain pharmaceutical products target replication enzymes of prokaryotes in order to target and kill microbes. These pharmaceuticals work by denaturing a specific target enzyme, making it nonfunctional. One such drug is incorrectly made and targets RNA polymerase in humans instead of in prokaryotes. Which of the following scenarios BEST explains the effect that the drug would have on DNA replication if it was ingested by a human?

The DNA will not be able to replicate due to the fact that DNA polymerase will be unable to bind to the DNA strands.

Cystic fibrosis (CF) is an autosomal recessive disorder that is caused by a mutation in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The CFTR protein is anchored to the membrane of cells in the sweat glands, lungs, and other exocrine glands, and it allows chloride ions to move out of cells which, in turn, causes water to leave the cells via osmosis. The most common mutation in the CFTR gene is called delta F508, which is a deletion of three nucleotides resulting in the loss of the amino acid phenylalanine on the CFTR protein. This abnormal CFTR protein breaks down shortly after it is made in the endoplasmic reticulum, so it never reaches the cell membrane. The result is the accumulation of chloride ions inside cells and the production of mucus on the cell surface that is abnormally thick and sticky. The abnormal mucus obstructs the airways and other glands, leading to impaired function of the lungs, pancreas, liver, kidneys, and intestine. When the CFTR protein is working correctly, as shown in Panel 1 below, chloride ions and water flow freely in and out of cells. However, when the CFTR protein is malfunctioning as in Panel 2, chloride ions and water cannot flow out of the cell. This causes Cystic Fibrosis, characterized by the accumulation of thick mucus outside of cells, particularly in the tissue that lines the respiratory tract. Which of the following statements BEST explains the cause of the abnormally thick and sticky mucus on the surface of respiratory and other tissues in patients with cystic fibrosis?

The accumulation of chloride ions inside the cell creates a hypertonic solution relative to the external cellular environment, which triggers the influx of water into the cell to maintain homeostasis. This causes the mucus on some tissues to become thick and sticky because the mucus is dehydrated.

Haploid yeast comes in two varieties, a-type cells and α α-type cells. The a cells produce a mating pheromone known as a-factor and have a surface protein known as STE2. The α α cells produce a mating pheromone known as α α-factor and have a surface protein known as STE3. The yeast cells release their mating factors into the surrounding area, as shown in the image. These signal molecules can be received by the STE receptor proteins on the membrane of the opposite haploid cell type, causing the receiving cell to grow a mating projection, known as a shmoo, in the direction the cell signal was received from. STE2 can only respond to α α-factor, and STE3 can only respond to a-factor, ensuring that the yeast mates with cells of the opposite type. Transcription of the genes for STE2 and STE3 are controlled by the MAT gene, which serves as a transcription factor. The allele MATa activates transcription of the genes for STE2 and a-factor while simultaneously repressing transcription of STE3. The allele MAT α α activates transcription of STE3 and α α-factor while simultaneously repressing transcription of STE2. If a researcher tested for the presence of particular genes, which of the following would be TRUE of a-type cells?

The cell would carry the genes for STE3, STE2, and α-factor but not the genes for MATα

Environmental factors that can influence the expression of genes include temperature, light, nutrients, metals, toxins, and signals from other cells. The lactose operon, or lac operon, is a cluster of genes found in prokaryotes to hydrolyze lactose into glucose and galactose. When lactose is present, the repressor will bind lactose and transcription will occur. However, the affinity of the lac operon's promoter to RNA polymerase is not strong so even in the presence of lactose, transcription is low. When lactose is absent, the repressor will bind the promoter and transcription is blocked. In the presence of both glucose and lactose, the lac operon is turned off. Glucose is easily metabolized and is the preferred energy source over lactose. Based on the diagrams, which of the following BEST explains why lactose is not metabolized in the presence of glucose?

The concentration of intracellular cAMP-CAP complexes is decreased.

Cystic fibrosis (CF) is an autosomal recessive disorder that is caused by a mutation in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The CFTR protein is anchored to the membrane of cells in the sweat glands, lungs, and other exocrine glands, and it allows chloride ions to move out of cells which, in turn, causes water to leave the cells via osmosis. The most common mutation in the CFTR gene is called delta F508, which is a deletion of three nucleotides resulting in an abnormal CFTR protein that breaks down shortly after it is made, so it never reaches the cell membrane. The result is an accumulation of chloride ions and water inside cells and the production of mucus that is abnormally thick and sticky because water is not available to dilute the mucous to normal consistency. The abnormal mucus obstructs the airways and other glands, leading to impaired function of the lungs, pancreas, liver, kidneys, and intestines. The diagram below shows a partial gene sequence for the normal cystic fibrosis transmembrane conductance regulator (CFTR) protein: Normal Nucleotide Sequence (sense strand, which is the same as the mRNA sequence): 5'-ATC-ATC-TTT-GGT-GTT-3' The three-base deletion that causes cystic fibrosis is shown in the partial gene sequence of nucleotide bases below: Mutant Nucleotide Sequence (sense strand, which is the same as the mRNA sequence): 5'-ATC-ATT-GGT-GTT-3' The chart below shows the amino acids produced by each possible combination of three RNA bases. Which of the following statements BEST explains how this deletion will affect the CFTR protein?

The deletion does not change any of the amino acids in the sequence, but the amino acid Phenylalanine (Phe) will be missing in the mutant protein.

tRNA is a type of molecule used by cells to transport amino acids from the cytosol to ribosomes for use in protein synthesis. Cells re-use individual tRNA molecules rather than synthesizing new tRNA molecules each time one is used. A class of enzymes called aminoacyl-tRNA synthetases bind specific free cytosolic amino acids to specific tRNA molecules. This endergonic reaction is powered by ATP. To begin, a specific synthetase's active site is shaped in such a way that an ATP molecule and a specific free amino acid can fit. The active site, in its initial conformation, does not have a region for a tRNA molecule to fit. Which of the following must occur before a tRNA molecule can become involved in a reaction?

The enzyme must use the ATP to phosphorylate the amino acid, which will induce a shape change in the active site of the enzyme that then allows the entry of the tRNA molecule.

Cystic fibrosis (CF) is an autosomal recessive disorder that is caused by a mutation in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The CFTR protein is anchored to the membrane of cells in the sweat glands, lungs, and other exocrine glands, and it allows chloride ions to move out of cells which, in turn, causes water to leave the cells via osmosis. The most common mutation in the CFTR gene is called delta F508, which is a deletion of three nucleotides resulting in the loss of the amino acid phenylalanine on the CFTR protein. This abnormal CFTR protein breaks down shortly after it is made in the endoplasmic reticulum, so it never reaches the cell membrane. The result is the accumulation of chloride ions and water inside cells and the production of mucus that is abnormally thick and sticky. The abnormal mucus obstructs the airways and other glands, leading to impaired function of the lungs, pancreas, liver, kidneys, and intestine. Children with cystic fibrosis are unable to get enough nutrients from food because of the lack of enzymes to help absorb fats and proteins and thus have difficulty growing and developing. Males with the disease are born sterile. When the CFTR protein is working correctly, as shown in Panel 1 below, chloride ions and water flow freely in and out of cells. However, when the CFTR protein is malfunctioning as in Panel 2, chloride ions and water cannot flow out of the cell. This causes Cystic Fibrosis, characterized by the accumulation of thick mucus outside of cells, particularly the tissue that lines the respiratory tract. Cystic fibrosis is the most common genetic disease affecting people of Caucasian European descent, with a carrier rate of 1 in 25 people. Since natural selection works by weeding less fit genetic variants out of a population, it is reasonable to assume that alleles with negative effects would be selected against and removed from a population, but this is not the case with many genetic diseases including cystic fibrosis and sickle cell anemia. Which of the following statements provides the MOST reasonable hypothesis that explains why cystic fibrosis has not been eliminated from the population by natural selection?

The mutant CFTR allele may confer a heterozygous advantage since recent studies have found that the mutant CFTR gene provides protection against the oftentimes fatal diseases of cholera, tuberculosis, and typhoid.

Pompe's disease is a hereditary disorder caused by a DNA mutation in which the individual is unable to correctly synthesize functional lysosomal enzyme alpha-glucosidase (GAA), the enzyme that normally allows the cells to break down glycogen for energy. How could a DNA mutation of this type produce the characteristics seen in those affected with this disorder?

The mutated form of the enzyme cannot effectively break down glycogen. Therefore, glycogen is stored in the body instead of being broken down for energy.

Epigenetics is the study of how external environments affect gene expression, leading to changes in genotypes and phenotypes without a change in the underlying DNA sequence. Two common epigenetic mechanisms are DNA methylation and histone acetylation, both of which affect the packaging of DNA around histone proteins, as illustrated in Figure 1 below. Honey bee populations are a classic example of epigenetic phenomena because females develop into two significantly different castes: worker bees and queen bees. All female bees are diploid, but there are major morphological, physiological and behavioral differences between queen bees and worker bees. Queen bees are the only bees in the colony that can reproduce, and worker bees are sterile and responsible for feeding and maintaining the colony. Phenotypic differences between queen and worker bees are indicated in the table below: Phenotype Worker Bee Queen Bee Mass at Emergence from Pupa 81 mg - 151 mg 178 mg - 292 mg Duration Larvae Fed Royal Jelly 3 days 6 days Lifespan 15 - 38 days (summer) 1 - 5 years Spermatheca (Sperm Receptacle and Storage) Undeveloped Large Ovaries Undeveloped Large Barbed Stinger Present Not Barbed Optimal Temperature of Larvae Development 33 C 33 C Which of the following statements provides the BEST scientific reasoning for the significant phenotypic differences between worker bees and queen bees?

The relatively large quantities of royal jelly fed to the queen trigger a cascade of molecular events that result in a lack of DNA methylation in genes that provide critical reproductive and other developmental functions.

There are three major types of Influenza viruses: Influenza A, Influenza B, and Influenza C. All three types of viruses cause flu-like symptoms in humans including fever, muscle aches, headache, and fatigue, but only Influenza A can infect humans and other mammals as well as birds. The letters H and N are included in naming many influenza viruses because the outer envelope of these viruses is covered with two types of glycoproteins, an H protein (hemogglutinin) and an N protein (neuraminidase). These glycoproteins enable viruses to bind to and fuse with the host cell plasma membrane. The H1N1 Influenza A virus was responsible for the 1918 and 2009 deadly worldwide pandemics, and genetic analysis revealed that H1N1 has a mixture of genetic material from pigs, birds, and humans. Which of the following BEST explains how some Influenza A viruses have genetic material from a variety of host species?

Viral genetic material could combine in a pig who is infected with both the pig flu and the bird flu viruses, and this recombinant strain can combine in a person who is infected with the human flu virus.