Genetics Exam 2

The term for when a piece of one chromosome attaches to another chromosome is __________. A) deletion B) inversion C) translocation D) duplication

C. translocation

Which of the following descriptions is NOT true of heterochromatin? A) It remains in a highly condensed state throughout the cell cycle. B) It makes up most chromosomal material and is where most transcription occurs. C) It exists at the centromeres and telomeres. D) It is characterized by the reduced crossing over and replication late in the S phase.

B. It makes up most chromosomal material and is where most transcription occurs.

In an individual with genotype Lpq / lPQ, what gamete genotypes would result from a single crossover between genes P and Q? A) LPQ and lpq B) LpQ and lPQ C) Lpq and lPQ D) lpQ and LPq E) cannot be determined

B. LpQ and lPQ

Which of the following describes how bacterial chromosomes are packaged/condensed? A) The DNA is wrapped around histone proteins and then organized into progressively thicker fibers. B) Negative supercoiling causes the DNA to twist on itself and the DNA is organized into loops to form a nucleoid. C) Topoisomerase introduces positive supercoils and the DNA is contained in a membrane bound nucleus. D) None of the above. Bacterial chromosomes are so small that no packaging is required.

B. Negative supercoiling causes the DNA to twist on itself and the DNA is organized into loops to form a nucleoid.

What would be the most likely effect of a deletion in the gene that encodes the RNA part of telomerase? A) The telomerase enzyme would be able to make only a few telomeric repeats before falling off. B) Telomerase would be unable to correctly associate with telomeres. C) The catalytic center of telomerase, the polymerase, would be altered. D) Telomerase would be unable to proofread its DNA product but would still synthesize telomeres.

B. Telomerase would be unable to correctly associate with telomeres.

An acentric fragment can be the result of crossing over between a normal chromosome and a chromosome that has undergone what kind of mutation? A) translocation B) pericentric inversion C) paracentric inversion D) duplication

C. paracentric inversion

Linked genes always exhibit... a. phenotypes that are similar b. a lack of recombinant offspring when a heterozygous parent is involved in a testcross. c. recombination frequencies of less than 50% d. a greater number of recombinant offspring than parental offspring when involved in a testcross.

C. recombination frequencies of greater than 50%

In Drosophila, the genes y, f, and v are all linked. y f v females are crossed to wild-type males and the F1 females are test-crossed. The F2 are distributed as follows: (see table in answer) Which of the three genes is located between the other two? A. y B. f C. v

C. v

A newly discovered species of dung beetle has 2n = 16 chromosomes. It mates with a closely related beetle species that has 2n = 12 chromosomes. How many chromosomes would there be in an amphidiploid beetle produced from this cross? A) 12 B) 14 C) 16 D) 28

D. 28

DNA polymerases require all of the following for DNA replication EXCEPT: A) a DNA template B) a free 3' OH C) a primer D) 3' to 5' polymerase activity E) dNTPs

D. 3' to 5' polymerase activity.

In the question above, how would you describe the arrangement of alleles in the F1 heterozygote? A) The alleles are in trans, a.k.a. repulsion. B) The alleles are in trans, a.k.a coupling. C) The alleles are in cis, a.k.a. repulsion. D) The alleles are in cis, a.k.a. coupling.

D. The alleles are in cis, a.k.a. coupling.

Positive interference... A) results in more double crossovers being observed than were expected. B) causes fewer single crossovers to be observed than were expected based on map distance. C) can be demonstrated by a coefficient of coincidence greater than 1. D) occurs when additional crossovers are inhibited near where a chiasma has already formed

D. occurs when additional crossovers are inhibited near where a chiasma has already formed.

In Griffith's experiments with Streptococcus pneumoniae, injection of which strain(s) caused the mouse to die? A) living type RII avirulent bacteria B) heat-killed type SIII virulent bacteria mixed with living type RII avirulent bacteria C) living type SIII virulent bacteria D) heat-killed type SIII virulent bacteria E) either B or C

E. either B or C

Using the data from the previous question, calculate the distance between f and v. A. 22 m.u. B. 15 m.u. C. 37 m.u. D. 20 m.u.

A. 22 m.u.

You are doing lab work with a new species of beetle. You have isolated lines that breed true for either blue shells (B) and long antenna (L) or green shells (b) and short antenna (l). Crossing these lines yields F1 progeny with blue shells and long antenna. Crossing F1 progeny with beetles that have green shells and short antenna yields the following progeny: blue shell, long antenna 82 green shell, short antenna 78 blue shell, short antenna 37 green shell, long antenna 43 Total 240 What is the map distance between the two genes? A) 33.3 m.u. B) 49.5 m.u. C) 8 m.u. D) 25 m.u.

A. 33.3 m.u.

Which of the following E. coli DNA polymerases has 5' to 3' exonuclease activity? A) DNA pol I B) DNA pol II C) DNA pol III D) all of the above

A. DNA pol I

How is DNA replication regulated in eukaryotes such as humans to ensure that each segment of the genome is copied exactly once during each cell cycle? A) Pre-replicative complexes that form at each origin during G1 phase give permission for that origin to replicate during S phase and cannot form again until the cell is back in G1. B) The replication fork progresses unidirectionally down each linear chromosome from one end to the other. C) Replication is only allowed to initiate at a single origin for each chromosome. D) DNA polymerase alpha remains bound to the newly synthesized DNA strand until replication of all genomic segments has fully completed.

A. Pre-replicative complexes that form at each origin during G1 phase give permission for that origin to replicate during S phase and cannot form again until the cell is back in G1.

The 11 nm chromatin fiber in eukaryotes is often described as looking like "beads on a string". What creates that appearance? A) The beads are the nucleosomes, and the string is the linker DNA. B) The beads are the heterochromatic regions that are tightly compacted, and the strings are euchromatic regions that are being actively transcribed. C) The beads are molecules of DNA polymerase that attach to the DNA string. D) The beads are ribosomes, and the string is the mRNA that has been transcribed from active chromatin

A. The beads are the nucleosomes, and the string is the linker DNA.

Assume that an individual of AB/ab genotype is involved in a testcross and four classes of testcross progeny are found in equal frequencies. Which of the following statements is TRUE? A) The genes A and B could be located on different chromosomes or very far apart on the same chromosome. B) The genes A and B are on the same chromosome and closely linked. C) The genes A and B fail to independently assort. D) The genes A and B must be located on different chromosomes.

A. The genes A and B could be located on different chromosomes or very far apart on the same chromosome.

Individuals that are euploid have... A) full sets of chromosomes, evenly divisible by n. B) more than two sets of chromosomes. C) missing or extra chromosomes. D) unbalanced, nonviable gametes.

A. full sets of chromosomes, evenly divisible by n.

The two strands of DNA in a double-helix have ________ polarity, so they are said to be ________. A) opposite, antiparallel B) the same, antiparallel C) opposite, complementary D) the same, complementary

A. opposite, antiparallel

Nondisjunction can occur at either the first or second division of meiosis. XYY individuals would most likely arise from nondisjunction at the ________ meiotic division in the ________. A) second, father B) second, mother C) first, father D) first, mother E) More than one of the choices could give rise to XYY individuals

A. second, father

In the diagram below, the * is marking the _____ end of the _________ strand. (see picture in answer) A) 5', leading B) 3', leading C) 5', lagging D) 3', lagging

B. 3', leading

How many different types of histone protein are there? A) 7 B) 5 C) 8 D) 4

B. 5

Genes R and S are linked and 10 map units apart. In the cross Rs/rS x rs/rs what fraction of the progeny will be RS/rs? A. 45% B. 5% C. 10% D. 25%

B. 5%

The Meselson and Stahl experiment starts with E.coli containing 15N/15N labeled DNA grown in 14N media. Which result did Meselson and Stahl observe by sedimentation equilibrium centrifugation to provide strong evidence for the semiconservative model of DNA replication? A) Both the first and second generation have both 15N/15N DNA and 14N/14N DNA. No hybrid 15N/14N DNA was observed. B) The first generation has hybrid 15N/14N DNA, and the second generation has both hybrid 15N/14N DNA and 14N/14N DNA. No 15N/15N DNA was observed. C) The first generation has hybrid 15N/14N DNA, and the second generation has hybrid 15N/14N DNA. No 15N/15N DNA or 14N/14N DNA was observed.

B. The first generation has hybrid 15N/14N DNA, and the second generation has both hybrid 15N/14N DNA and 14N/14N DNA.

Hybrids in which the chromosome sets come from two distinct, though related, species are known as ___________. A) bivalents B) allopolyploids C) autopolyploids D) ambiploids

B. allopolyploids

The pyrimidine bases are ________. A) cytosine and guanine B) cytosine, thymine, and uracil C) adenine and thymine D) adenine and guanine

B. cytosine, thymine, and uracil

Unequal crossing over often results in what type(s) of chromosomal condition? A) polyploidy B) duplications and deletions C) inversion D) translocation

B. duplications and deletions

Okazaki fragments are associated with _____________. A) dispersive replication B) lagging strand synthesis C) leading strand synthesis D) homologous recombination

B. lagging strand synthesis

During DNA replication in E. coli, primase is responsible for . . . A) unwinding the DNA double helix. B) synthesizing RNA primers. C) replacing RNA primers with DNA. D) relaxing the supercoiled DNA.

B. synthesizing RNA primers

Edwards and Patau syndromes are caused by ________. A) monosomy B) trisomy C) deletions D) sex chromosome aneuploidy

B. trisomy

A map distance of 23 centiMorgans between two genes indicates which of the following? A) There are 23 other genes between the two genes of interest. B) A crossover occurs between the genes in 23% of the meiotic tetrads involving that pair of homologous chromosomes. C) 23% of the offspring exhibit recombination between the two genes. D) The physical distance between the genes is 23 nanometers.

C. 23% of the offspring exhibit recombination between the two genes.

According to Chargaff's rule, if the DNA of a species contains 20% adenine, what percent of guanine will it contain? A) 50% B) 20% C) 30% D) 75%

C. 30%

How is DNA synthesis similar in prokaryotes and eukaryotes? A) Synthesis involves the action of telomerase enzyme. B) Synthesis proceeds from multiple replication origins. C) Synthesis is continuous on one strand and discontinuous on the other. D) All of the above

C. Synthesis is continuous on one strand and discontinuous on the other.

Which DNA molecule form is a left-handed helix? A) B DNA B) A DNA C) Z DNA D) none of these

C. Z DNA

What is attached to the 2' carbon of the sugar in a DNA nucleotide? A) an OH group B) a nitrogenous base C) a hydrogen atom D) a phosphate group

C. a hydrogen atom

Experiments by Barbara McClintock and Harriet Creighton demonstrated that... a. DNA is replicated semiconservatively. b. the frequency of recombination between two genes on a chromosome is directly proportional to the distance between them. c. genetic recombination involves the physical exchange of material between homologous chromosomes. d. DNA is the genetic material in T2 bacteriophage.

C. genetic recombination involves the physical exchange of material between homologous chromosomes.

Given the following sequence of genes on a chromosome, determine what change in chromosome structure occurred. (the * indicates the centromere) before A B C D * E F G H after A C D * E F G H A) gene duplication B) inversion C) intercalary deletion D) terminal deletion

C. intercalary deletion

Typically, only ~50% of gametes produced by an individual who is heterozygous for a reciprocal interchromosomal translocation are viable. This is because... A) non-disjunction of homologous chromosomes in meiosis I causes two of the four gametes from each meiosis to be aneuploid. B) only half of the gametes produced by adjacent segregation have normal chromosomes. C) only alternate segregation, which occurs in roughly half of the meioses, produces gametes with exactly one copy of each gene. D) only two of the four chromosomes pair at metaphase of meiosis II.

C. only alternate segregation, which occurs in roughly half of the meioses, produces gametes with exactly one copy of each gene.