Question 1

In Drosophila, the two genes v and sn are X-linked and 25 map units apart. A female fly of genotype $$v^+ sn / v sn^+ is $$crossed to a male from a wild-type line. What percent of male progeny will be $$v sn$$?

Accepted Answer

12.5

Question 2

In maize, two plants that are heterozygous for the recessive alleles a and b are crossed. What frequency of double-mutant progeny will appear if a and b are 7.2 map units apart, and both parents carry a and b in trans (configuration)?

Accepted Answer

0.0625

Question 3

The following recessive alleles are found in corn: g, glossy leaf and r, red aleurone. A hybrid of unknown origin is testcrossed, with the following 1,000 progeny resulting: red, 127; glossy, 153; wild-type, 352; and glossy + red, 368. Which of the following could have been a parent of the dihybrid, assuming the parents were homozygous?

Accepted Answer

+, red

Question 4

The following recessive alleles are found in corn: g, glossy leaf and r, red aleurone. A hybrid of unknown origin is testcrossed, with the following 1,000 progeny resulting: red, 127; glossy, 153; wild-type, 352; and glossy + red, 368. What is your best estimate of the map distance between glossy and red, in map units?

Accepted Answer

12.7

Question 5

Genes a and b are 10 map units apart, b and c are 20 map units apart, and a and c are 30 map units apart. If a triple heterozygote is testcrossed, among 1,000 progeny, how many are expected to result from double crossovers if there is no interference?

Accepted Answer

20

Question 6

Genes a and b are 10 map units apart, b and c are 20 map units apart, and a and c are 30 map units apart. If a triple heterozygote is testcrossed, among 1,000 progeny, how many are expected to result from double crossovers if interference = 0.5?

Accepted Answer

10

Question 7

Genes a and b are 10 map units apart, b and c are 20 map units apart, and a and c are 30 map units apart. If a triple heterozygote is testcrossed, among 1,000 progeny, how many are expected to result from single crossovers between a and b if there is no interference?

Accepted Answer

40

Question 8

Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a), hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that was testcrossed, the phenotypes in figure 5 below were observed. What is the linkage arrangement of these three loci?

Accepted Answer

a-h-j

Question 9

Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a), hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that was testcrossed, the phenotypes in figure 5 above were observed. If the parentals (P1) were homozygous, which of the following could have been a parent?

Accepted Answer

anthocyaninless, jointless

Question 10

Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a), hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that was testcrossed, the phenotypes in figure 5 above were observed. What is your best estimate of the anthocyaninless-hairless distance?

Accepted Answer

20.0

Question 11

Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a), hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that was testcrossed, the phenotypes in figure 5 above were observed. What is your best estimate of the anthocyaninless-jointless distance?

Accepted Answer

35.2

Question 12

Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a), hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that was testcrossed, the phenotypes in figure 5 above were observed. What is your best estimate of the hairless-jointless distance?

Accepted Answer

37.6

Question 13

Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a), hairless plants (h), and jointless fruit stems (j). Among 3,000 progeny from a trihybrid F1 that was testcrossed, the phenotypes in figure 5 above were observed. Approximately what is the coefficient of coincidence?

Accepted Answer

0.4

Question 14

If the phenotype of a bacterial strain is $$Met^-$$, it

Accepted Answer

requires methionine for growth

Question 15

A bacterial cell with the phenotype $$F^+$$

Accepted Answer

can donate the F factor during conjugation

Question 16

A bacterial cell with the phenotype Hfr

Accepted Answer

can donate the host chromosome during conjugation

Question 17

The Hershey and Chase experiment with $$^{32}P$$ and $$^{35}S$$ demonstrated that

Accepted Answer

phage DNA enters the host cell

Question 18

Antiparallel means that

Accepted Answer

DNA strands run in opposite directions

Question 19

If DNA polymerase III could add bases in the 3' to 5' direction in E. coli, there would be no need for

Accepted Answer

Okazaki fragments

Question 20

Primer removal and gap filling in the completion of an Okazaki fragment is done primarily by

Accepted Answer

DNA polymerase I

Question 21

The final covalent bond made in the completion of an Okazaki fragment, including primer removal and gap filling, is made by

Accepted Answer

DNA ligase

Question 22

Histones interact with DNA to form

Accepted Answer

nucleosomes

Question 23

How many molecules of histones H1, H2A, H2B, H3, and H4, respectively, make up a nucleosome?

Accepted Answer

two each

Question 24

The second-order (highest-order) fiber of a eukaryotic chromosome, the second solenoid-like coiling of the nucleosomed DNA, is approximately how wide, in Å?

Accepted Answer

110

Genetics Exam Practice: Linkage, Mapping, Bacterial Genetics, and DNA Replication

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