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Genetics Final Fall 2021

Terms in this set (56)

1. What is the function of single stranded binding proteins?
prevent the formation of secondary structures within single-stranded DNA
1. DNA Polymerase I and DNA Polymerase III both have ____ activity but only DNA polymerase I has _____ activity
3'-5' exonuclease, 5'-3' exonuclease
1. The Holliday model describes which of the following processes?
homologous recombination
1. What is the function of DNA gyrase?
reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding
1. The nuclear genome of a single human cell (i.e., the entire diploid complement) contains about 6.6 billion (6.6 × 109) base pairs of DNA. If synthesis at each replication fork moves along the template at an average rate of 50 nucleotides per second and all the DNA is replicated in 5 minutes, how many origins of replication exist in a human diploid cell? Assume that replication is initiated simultaneously at all origins.
220,000
1. Approximately 6.6 Gb of DNA is present in a single-celled human zygote and must be replicated faithfully at each cell division. What is the approximate size of the haploid human genome?
C. 3.2 Gb
1. You learn that a Mars lander has retrieved a bacterial sample from the polar ice caps. You obtain a sample of these bacteria and perform the same kind of experiment that Meselson and Stahl did to determine how the Mars bacteria replicate their DNA. Based on the following equilibrium density gradient centrifugation results, what type of replication would you propose for these new bacteria?
E. dispersive
1. Which of the results (A through F) would give a clear experimental comparison to distinguish between the semiconservative model and dispersive model?
B. D and E
1. Which of the following does NOT utilize bidirectional replication?
A. rolling circle model
A. rolling circle model
1. You are studying a new virus with a DNA genome of 12 Kb. It can synthesize DNA at a rate of 400 nucleotides per second. If the virus uses rolling-circle replication, how long will it take to replicate its genome? Answer only for the first strand; ignore replication along the displaced strand.
C. 30 seconds
1. Okazaki fragments are found in all of the following EXCEPT in
C. the leading strand
1. Which activity is NOT associated with DNA polymerases?
D. ability to synthesize a DNA from scratch without a primer
1. The diagram shown below is one half of a replication bubble. As the DNA template strands unwind toward the right, new strands of DNA get synthesized. Which of the following represents a lagging strand?
A. B
1. _____ are tandemly repeated DNA sequences located at the ends of eukaryotic chromosomes?
C. telomeres
1. For which of the following is the "end-replication problem" relevant?
C. linear chromosomes
1. Which of the following typically only have one origin of replication?
C. prokaryotes
1. If ribonucleotides were depleted from a cell during S phase, how would DNA synthesis be affected? (Ignore energetic considerations.)
B. Replication would cease because ribonucleotides are required to initiate DNA synthesis.
1. During DNA replication, the synthesis of the new strand requires the addition of a new dNTP to the 3'-OH group of the growing nucleotide strand by DNA polymerase. Which of the following provides the energy needed for this step?
E. cleavage of two phosphate groups from the dNTP
1. The radioactive labeling experiment similar to Meselson and Stahl's experiment was performed to determine what happens to histone proteins in eukaryotic DNA replication. Pre-existing and newly synthesized histone proteins were labeled with radioactive isotopes of different atomic mass. Select the statement(s) that are consistent with the diagram shown. (Select all that apply.)
A. The newly synthesized histone and preexisting histones tend to mix together and reassociate with DNA after each round of the replication.
D. The newly synthesized histone and preexisting histones mix and form smeared bands, representing heterogeneous mixture
1. Which statement CORRECTLY describes why the DNA synthesis is discontinuous on one template strand while continuous on the other? (Select all that apply.)?
D. It is due to the antiparallel nature of the DNA molecule.
E. It is due to the nature of the DNA polymerase which can only add new nucleotides at the 3' end
1. Which of the following statements does NOT describe a challenge of working at the molecular level?
C. it is not possible to isolate DNA in a stable form
1. A gene does not contain the necessary restriction enzyme sites for cloning into a plasmid vector. What is a possible option?
C. Use PCR to amplify the gene while also incorporating new restriction enzyme sites at the end of the PCR products
1. Which of the following is NOT used in an in situ hybridization experiment for visualizing DNA?
A. antibody
All of the following are required to create a cDNA library EXCEPT:
B. RNA polymerase
1. Which of the following BEST describes knockout mice?
C. They have a gene of interest that has been fully disabled
1. What is the purpose of Taq polymerase in a PCR reaction?
B. DNA synthesis
1. Which of the following represents an appropriate cloning vector for cloning a gene into a bacterial cell?
B. plasmid
1. Consider a tobacco plant cell that was able to express a toxin that was lethal to insects and was resistant to the antibiotic kanamycin. Which of the following genes would this cell contain?
D. Bt and a kanamycin resistance gene product only
1. Which of the following can be used for genetic engineering in plants?
C. Ti plasmids, Rhizobium radiobacter, and selectable markers
1. You identify an RFLP in mice by digesting genomic DNA with HindIII enzyme and radiolabeling a piece of probe DNA. Southern blot analysis shows that the probe detects a 2-kb fragment in one strain of mice and a 4-kb fragment in another strain of mice. The two mice strains are crossed to produce an F1 generation. Two F1 siblings are mated to produce a dozen F2 progeny. You isolate genomic DNA from several F1 and F2 individuals, digest with HindIII, and perform a Southern blot with the same probe. How many bands would be seen in the Southern blot of an F1 individual?
C. two
1. A scientist is studying a normal tissue sample and a cancerous tissue sample. What method might she use to determine whether the transcription of gene X is upregulated in the cancerous tissue sample?
F. carrying out reverse transcription quantitative PCR (RT-qPCR) using both samples
1. A scientist edits a mammalian genome by inserting a GFP reporter sequence downstream of a gene of interest. Which of the following methods is she likely to have used to make this change?
C. CRISPR-Cas9 genome editing followed by homologous recombination (HR) with a donor template
1. Which of the following is a set of molecular techniques for locating, isolating, altering, and studying DNA segments?
A. recombinant DNA technology
1. What is the function of dideoxynucleotides in Sanger DNA sequencing?
C. They stop synthesis at a specific site, so the base at that site can be determined
1. A student carries out PCR using the following steps:Step 1: 94°C for 1 minuteStep 2: 60°C for 30 secondsStep 3: 72°C for 30 secondsWhich of the following lists the CORRECT terms for these three steps?
A. denaturation of the double-stranded template, primer annealing, extension of the new DNA molecules
1. During gel electrophoresis, large DNA fragments will _____ small DNA fragments
B. migrate more slowly than
1. A gene in the fruit fly D. melanogaster is found to affect neuronal function when mutated. A homologue of this gene is identified in mice. Which of the following methods would it make most sense for a scientist to use to study the function of the gene in mice? (Select all that apply.)
A. CRISPR-Cas9 genome editing targeting the gene of interest followed by homologous recombination (HR) with a donor template
B. reverse genetics
C. CRISPR-Cas9 genome editing targeting the gene of interest followed by nonhomologous end joining (NHEJ)
1. A student carries out PCR using the following steps:Step 1: 94°C for 1 minuteStep 2: 60°C for 30 secondsStep 3: 72°C for 30 secondsAfter subjecting his PCR reaction to gel electrophoresis, the student sees no PCR product on the gel. What error(s) might he have made? (Select all that apply.)
D. He carried out step 3 for too short a time.
E. He carried out step 2 at too high a temperature
1. A scientist wishes to screen a DNA library for a gene of interest which has not yet been isolated. Which of the following are strategies she could use? (Select all that apply.)
A. If the gene of interest produces a protein and its amino acid sequence is known, she could create a pool of synthetic probes corresponding to all possible nucleotide sequences that would express that protein or peptide.
C. She could create a probe using a similar gene from another organism
D. If a gene of interest produces a protein, she could use antibodies that recognize the protein of interest if the DNA library was an expression library.
1. Which agent of evolution tends to reduce genetic variation between populations and increase genetic variation within each population?
E. migration
1. ____ ultimately produces all new genetic variation in a population.
D. mutation
1. If there is random mating in a population and no evolutionary forces are acting on the population, what will be the expected outcome?
B. Both the genotypic distribution and the allelic frequencies will remain the same.
1. _____ occurs when one allele or trait is favored over another?
C. directional selection
1. By the early 1980s, the population of Florida panthers had dwindled to fewer than 30. Within this population, there was a high frequency of detrimental traits, including low sperm count and undescended testicles in males and kinked tails in both sexes. The future for this iconic population was bleak at best. Which of the following is the BEST solution that would both increase the likelihood that the population would survive and preserve the genetic identity of this unique population?
C. Genetic rescue could be performed, in which panthers from another population would be introduced in order to bring in new genetic variation and to reduce the genetic load.
1. Through _____, alleles may disappear from a population simply by chance.
B. genetic drift
1. Which agent of evolution is most likely responsible for the decrease in the frequency of a detrimental recessive allele as shown in the accompanying chart?
A. Natural selection
DNA typing is used to compare evidence DNA (E) left at a crime scene to two suspects (S1 and S2). Suspect 1 is excluded by the evidence, but suspect 2 remains included. What is the frequency of suspect 2's genotype if the allelic frequencies in the population are f(A1) = 0.1, f(A2) = 0.2, and f(A3) = 0.7, and the population is at Hardy-Weinberg equilibrium?
A. 0.04
_____ is the movement of genes between populations.
A. Migration
In overdominance, the HIGHEST fitness is found in which genotype?
A. Heterozygote
When a population is in Hardy-Weinberg equilibrium, what is the approximate frequency of the aa homozygote and the Aa heterozygote when the frequency of AA is approximately 0.5?
A. aa = 0.1, Aa = 0.4
_____ is the product of sampling errors and chance events that may result in changes in allelic frequencies.
C. genetic drift
Human blood type is determined by three alleles, IA, IB, and IO. The alleles IA and IB are co-dominant to each other, and both are dominant to IO. Within a large, randomly mating population (540,000 individuals), the frequencies for the blood type alleles are 0.3 for the IA allele, 0.6 for the IO allele, and 0.1 for the IB allele. What percentage of the type B people are heterozygotes (IBIO)?
60%
_____ increases the frequency of homozygotes in a population compared to the results of random mating.
C. inbreeding
Mutation has what effect on a population?
B. it creates or increases genetic variation
A population that goes through a dramatic reduction in size will experience:
C. genetic bottleneck
What molecular factors can lead to genetic variation in populations beyond that observable by phenotype? (Select all that apply.)
B. Synonymous codons.
C. Sequence changes in introns that don't affect a gene product.
D. Sequence changes in intergenic DNA
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