ap bio unit 6 mcq on ap classroom
The processes illustrated in the models depicted above all result in which of the following? Crossing over; conjugation; fertillization
An increase in genetic variation
Some strains of the bacterium Streptococcus pyogenes secrete poisonous substances called exotoxins. The genes encoding the exotoxins are thought to have originated in bacteriophages, which are viruses that infect bacteria. Which of the following is the most likely mechanism by which the S. pyogenes acquired the ability to produce the exotoxins?
Bacteriophage DNADNAbecame integrated in the bacterial chromosome.
Enzyme used to position nucleotides during DNA replication
DNA Polymerase
In the 1940's, Avery MacCleod, and McCarty transformed nonencapsulated bacteria into encapsulated forms by growing the nonencapsulated cells in a culture containing an extract made from dead encapsulated cells. A reasonable conclusion to draw from the results of the experiment is that
DNA is the genetic material
Enzyme used during replication to attach Okazaki fragments to each other
DNA ligase
Which of the following is most likely to create genetic variation in a population?
DNA polymerase errors during replication
Which of the following correctly explains where DNA replication will begin on the strand oriented 5'→3'5′→3′, reading from left to right?
DNA replication will be initiated immediately to the left of the RNA, since DNA polymerase requires an RNA primer.
The human TPM1���1 gene encodes members of the tropomyosin family of cytoskeletal proteins. Which of the following best explains how different proteins can be made in different cell types from the one TPM1���1 gene?
Different exons are retained or spliced out of the primary transcript
As represented in Figure 1 and Figure 2, the phenotypic difference between marine and freshwater sticklebacks involves Pitx1, a gene that influences the formation of the jaw, pituitary gland, and pelvic spine. Enhancer sequences upstream of the Pitx1 genetic locus regulate expression of the Pitx1 gene at the appropriate times and in the appropriate tissues during development. Previous studies have found that a mutation in the hindlimb enhancer interferes with the formation of a pronounced pelvic spine. Which of the following best describes how sticklebacks in the same population with identical copies of the Pitx1 gene can still show phenotypic variation in the pelvic spine character?
Expression of the Pitx1 gene is affected by mutations at other genetic loci.
The table below describes the action of two genes involved in the regulation of nervous system development in the nematode C. elegans.Which of the following claims is best supported by the data?
Gene A promotes neuron development; gene B promotes programmed cell death in neuronal precursors.
Histone methyltransferases are a class of enzymes that methylate certain amino acid sequences in histone proteins. A research team found that transcription of gene R� decreases when histone methyltransferase activity is inhibited. Which scientific claim is most consistent with these findings?
Histone methylation opens up chromatin at gene R� so transcription factors can bind to DNADNA more easily.
Methicillin-resistant Staphylococcus aureus (MRSA) can be a serious threat to human health. There is evidence that S. aureus infections are common in hospitals and that MRSA have become resistant to other antibiotics besides methicillin. This suggests that the rapid evolution of resistance in the bacteria poses a serious public-health challenge. Which of the following best explains the ability of MRSA to evade existing drug therapies?
MRSA exchange genetic material with other antibiotic-resistant bacteria, which can spread resistance in the S. aureus population.
image shows model of process with nucleic acids; replication fork etc. Which of the following best explains what process is represented in Figure 1 ?
New DNA strands are being synthesized in the 5'5′ to 3'3′ direction from their DNA templates.
pre-mRNA--> mRNA (step 2) Which of the following best describes an event during step 2 in the simplified model above?
Noncoding sequences are removed from a newly synthesized RNA molecule.
The p53p53 protein regulates a cellular response to DNADNA damage. Based on the diagram above, which of the following best describes the role of p53p53 in the response to DNADNA damage?
Phosphorylated p53p53 stimulates transcription of p21p21, and the resulting p21p21 protein suppresses cell division until the DNADNA damage is repaired.
Which of the following statements best explains how protein X regulates gene expression?
Protein X is responsible for activating transcription of some genes but not others.
A new mutation that arose in one copy of gene X in a somatic cell resulted in the formation of a tumor. Which of the following pieces of evidence best describes how the new mutation directly caused the tumor?
Protein X normally stimulates cell division, and the mutation created an overactive version of protein X.
Which of the following biotechnology approaches could be used to identify ferritin mRNA in a sample of total cellular RNA?
RNA samples could be separated by size using agarose gel electrophoresis and incubated with labeled single-stranded DNA molecules that are complementary to the ferritin mRNA.
Erwin Chargaff investigated the nucleotide composition of DNADNA. He analyzed DNADNA from various organisms and measured the relative amounts of adenine (AA), guanine (GG), cytosine (CC), and thymine (TT) present in the DNADNA of each organism. Table 1 contains a selected data set of his results. Which of the following statements best explains the data set?
Since the %A%A and the %T%T are approximately the same in each sample, adenine and thymine molecules must pair up in a double-stranded DNADNA molecule.
Antibiotics interfere with prokaryotic cell functions. Streptomycin is an antibiotic that affects the small ribosomal subunit in prokaryotes. Specifically, streptomycin interferes with the proper binding of tRNAtRNA to mRNAmRNA in prokaryotic ribosomes. Which of the following best predicts the most direct effect of exposing prokaryotic cells to streptomycin?
Synthesis of polypeptides will be inhibited.
Tay-Sachs disease is a rare inherited disorder caused by an autosomal recessive allele of the HEXA gene. Affected individuals exhibit severe neurological symptoms and do not survive to reproductive age. Individuals who inherit one copy of the allele (Tay-Sachs carriers) typically show no symptoms of the disorder. The frequencies of Tay-Sachs carriers in the general population of North America and in three different subpopulations are presented in the table.Based on the information presented, which of the following best explains the difference in phenotype between Tay-Sachs carriers and homozygous recessive individuals?
Tay-Sachs carriers synthesize an essential enzyme that homozygous recessive individuals cannot synthesize.
Retroviruses have an RNA genome. HTLV-1 is a lysogenic retrovirus that establishes a latent infection in human cells. By which of the following mechanisms does infection by a retrovirus such as HTLV-1 most likely cause long-lasting genetic changes to host cells?
The RNA viral genome is reverse transcribed into DNA that integrates into the host genome.
The figure above depicts the DNA-protein complex that is assembled at the transcriptional start site of gene X when the expression of gene X is activated in liver cells. Previous studies have shown that gene X is never expressed in nerve cells. Based on the diagram, which of the following most likely contributes to the specific expression pattern of gene X ?
The activator is a sequence-specific DNA-binding protein that is present in some tissues but not in other tissues.
The bacterium Vibrio cholerae is harmless unless a lysogenic bacteriophage provides the gene coding for the cholera toxin, which converts the bacterium to the virulent form that causes cholera. Which of the following best explains how the gene encoding cholera toxin becomes part of the bacterial genome?
The bacteriophage inserts the toxin gene into the host cell DNA, and the gene is expressed with the rest of the host cell's genes.
Arctic foxes typically have a white coat in the winter. In summer, when there is no snow on the ground, the foxes typically have a darker coat. Which of the following is most likely responsible for the seasonal change in coat color?
The decrease in the amount of daylight in winter causes a change in gene expression, which results in the foxes growing a lighter-appearing coat.
Which of the following is the most likely effect of the mutation at nucleotide position 7 in the GULO gene of humans?
The deletion of the single nucleotide causes a frame shift, changing the primary structure downstream of the mutation and resulting in a nonfunctional protein.
A researcher claims that Tay-Sachs carriers are protected against the infectious disease tuberculosis (TB). Which of the following observations about the annual incidence of tuberculosis in subpopulation II could best be used to support the researcher's claim?
The incidence of TB in subpopulation II is lower than the incidence of TB in the general population.
During the formation of vertebrae, the most anterior embryonic segment that expresses Hoxc6 marks the end of the cervical (neck) vertebrae and the beginning of the thoracic (rib) vertebrae. All mammals have seven cervical vertebrae. Which of the following statements is most likely to be true?
The most anterior expression of Hoxc6 is the eighth vertebra in mammals.
The TAS2R38 receptor protein has been detected on the surface of cells from individuals who are homozygous for the nontaster allele of the TAS2R38 gene. Which of the following is the most likely effect of the mutations associated with the nontaster allele on TAS2R38 gene expression?
The mutations change the primary structure of the encoded receptor protein.
The following the DNA sequence is a small part of the coding (nontemplate) strand from the open reading frame of β-hemoglobin gene. Given the codon chart listed below, what would be the effect of a mutation that deletes the G at the beginning of the DNA sequence?
The reading frame of the sequence would shift, causing a change in the amino acid sequence after that point.
Process in which RNA is produced by using a DNA template
Transcription
Gibberellic acid stimulates the cells of germinating grass seeds to produce mRNA molecules that code for hydrolytic enzymes. In this case the role of gibberellic acid can best be described as that of
a regulator of gene activity
Cells that contain only circular chromosomes are most probably which of the following?
bacterial cells
A sterile agar plate, I, is streaked with a pure culture of bacteria by means of aseptic techniques. Paper discs treated with the antibiotics Aureomycin (A) and penicillin (P) are placed at opposite sides of the plate, as shown in the diagram above. The plate is examined after a 24-hour incubation period, and a clear ring is discovered around disc A, but not around disc P. Within the clear ring around disc A, a single bacterial colony with physical characteristics like those of the pure culture is observed. A second sterile agar plate, II, is then streaked with this single colony and also incubated with antibiotics. The single colony found within the clear ring in plate I is most likely made up of the descendants of a bacterial cell that
contained information conferring resistance to Aureo-mycin
During the infection cycle for a typical retrovirus, such as HIV, which uses RNA as genetic material, the genetic variation in the resulting population of new virus particles is very high because of
errors introduced in the DNA molecule through reverse transcription This option is correct. The process of reverse transcription does not involve proofreading.
Sickle-cell anemia results from a point mutation in the HBB gene. The mutation results in the replacement of an amino acid that has a hydrophilic R-group with an amino acid that has a hydrophobic R-group on the exterior of the hemoglobin protein. Such a mutation would most likely result in altered
properties of the molecule as a result of abnormal interactions between adjacent hemoglobin molecules
The diagram below illustrates the results of electrophoresis of DNA sequences obtained from a family of two adults and three children, and amplified using PCR. The bands represent short repeating sequences of variable length. Results for another female (X) are included for comparison. The banding patterns of the DNA fragments reveal that
the mother cannot be the biological parent of all three children
process in which naked DNA is taken up by a bacterial or yeast cell
transformation