Exam 2 Version 2

A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines. This DNA molecule could be comprised of

120 thymines and 120 adenines.

Use the narrative above. What is the distance between these genes on a genetic map?

25 mu

Which nucleotide sequence represents the complement to the DNA strand 5' - AGATCCG- 3'?

3' - TCTAGGC- 5'

DNA polymerase moves along the template strand of DNA in the _______ direction, and adds nucleotides to the ______ end of the newly synthesized strand

3' to 5'; 3'

Cytosine makes up 20% of the nucleotides in a sample of DNA from a cellular organism. Approximately, what percentage of the nucleotides in this sample will be thymine?

30

In a two-point test cross, 36 of the offspring were recombinant types. The remaining 64 offspring were parental types. How many map units separate the two loci?

36

Refer to Figure 1. Which letter or a combination of letters would you expect to indicate a position(s) where a topoisomerase is required?

A

Refer to Figure 2. Between which two genes would you expect the highest frequency of recombination?

A and G

Which of the following is false about an individual with karyotype B (right)?

A female with Down syndrome resulting from monosomy 21

Vestigial wings is a recessive trait.

A. CROSS I results give evidence supporting the statement.

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium for one generation. Which pattern in the figure above would you expect if the DNA was replicated in a conservative manner?

B

These two genes are not linked.

C. CROSS II results give evidence supporting the statement.

The distance between the two genes is 25 mu

D. CROSS II results give evidence against the statement.

Which of the following statements about DNA is false?

DNA is only found in eukaryotic cells

RNA primers are used in DNA replication because

DNA polymerase cannot initiate DNA synthesis without a primer.

Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila by showing that

Drosophila genes cluster into four distinct groups of linked genes.

In an analysis of the nucleotide composition of DNA, which of the following is true?

G+A=T+C

Based on Mark's karyotype what is his "phenotype"

He has Klinefelter syndrome

Why is an intact, linear double helix an ineffective template for DNA polymerase?

It has a 3'-hydroxyl group, but lacks a template

Which of the following is true about an individual with karyotype A (left)?

Male with Down syndrome

If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis?

One gamete will be n+1, one will be n-1, and two will ben.

Hershey/Chase experiments (using T2 bacteriophages labeled with radioactive sulfur and radioactive phosphorus) demonstrated all of the following except:

RNA is the genetic material of T2 phages.

what is a possible explanation for Mark's karyotype and colorblindness?

Sex chromosome nondisjunction during meiosis I of oogenesis Sex chromosome nondisjunction during meiosis II of oogenesis

Which of the following statements about human telomeres is correct?

They contain multiple copies of a short DNA sequence. They are present at the ends of eukaryotic chromosomes. They can be extended by an enzyme called telomerase.

Which of the following is the term that best describes a human cell that contains 22 pairs of autosomes and one sex chromosome?

Turner female somatic cell

refer to Figure 2. If you performed a three point testcross involving genes W, E and G and none of the 25,000 progeny corresponded to DCOs (double cross overs) what would be the approximate value of interference?

about 1

Two chains of DNA must run in ______direction(s) and must be __________if they are to bond with each other.

antiparallel; complementary

Which of the following abnormalities is most likely to be lethal to a human cell?

autosomal monosomy

Statement A. Allotertaploid plants are more likely to be fully fertile than autotetraploids. Statement B. Triploid plants are usually sterile and produce few or no seeds

both are true

Refer to Figure 1. At which letter or letter combination would you expect to see a discontinuous synthesis of DNA (the lagging strand)?

c and d

use the narrative above. The alleles in the female parent are in a ________________ configuration as indicated by the most numerous progeny classes that represent _________________.

cis or coupled/non recombinants

Refer to Figure 7. The structures represented by the letter E are:

composed of dna and rna, called okazaki fragments

The DNA strand growing toward the replication fork grows ______ in a 5'—>3' direction as the replication fork advances and is called the ________.

continuously, leading strand

What is the mechanism for the production of genetic recombinants?

crossing over and independent assortment

A nonreciprocal (unequal) crossover causes which of the following products?

deletion, duplication

After mixing a heat-killed, tetracycline resistant strain of bacteria with a living tetracycline (tet) sensitive strain, you discover that some of the living cells are now tetracycline resistant. The best evidence that the ability to survive in the presence of tetracycline is a heritable trait would be an observation that

descendants of the living tet resistant cells are also tet resistant

a tetraploid organism could have a maximum of ____________ different alleles for a particular locus

four

The principle of independent assortment is violated by:

gene linkage

Refer to Figure 2. If you performed a two-point testcross involving genes A and G and obtained only 17% recombinant progeny what would be the most likely reason for this discrepancy from the map in the figure 2.

increase of nonrecombinant chromosomes resulting from double cross overs

Which of the following is inconsistent with the Central Dogma

information in proteins can be perpetuated

One possible result of chromosomal breakage can be that a fragment reattaches to the original chromosome in a reverse orientation. This is called

inversion

Autosomal monosomy is not seen in live births because:

its effects are so lethal as to cause spontaneous abortion early in pregnancy

Refer to Figure 2. If you performed a three point testcross involving genes W, E and G what fraction of the progeny would be expected to represent DCOs (double cross overs)?

less than 0.5%

Use the information from previous question but assume two rounds of replication in the presence of N14. Which pattern in the figure above would you expect if the DNA was replicated in a dispersive manner?

none of the above

The two molecules that alternate to form the backbone of a polynucleotide chain are:

sugar and phosphate

Refer to Figure 7. The correct designation for the structure or position labeled C is:

template

The leading and the lagging strands differ in that

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction. the leading strand is synthesized continuously, whereas the lagging strand is synthesized in short fragments that are ultimately stitched together.

What determines the nucleotide sequence of the newly synthesized strand during DNA replication?

the nucleotide sequence of the template strand

Tobacco mosaic virus has RNA rather than DNA as its genetic material. In a hypothetical situation where proteins from a tobacco mosaic virus were mixed with DNA from a related DNA virus, the result could be a hybrid virus. If that virus were to infect a cell and reproduce, what would the resulting "offspring" viruses be like?

the related DNA virus

Enzymes called ____________ form nicks in the DNA molecules, thereby preventing the formation of knots in the DNA helix during replication.

topoisomerases

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. This is called a (an)

translocation

A cell that has 2n + 1 chromosomes is

trisomic, aneuploid

A dividing eukaryotic cell lacking telomerase activity would

undergo a reduction in chromosome length.

Which two genes are closest together on the genetic map?

v and s

What is the order of the genes on the chromosome?

v-s-ct