Question 1

Three recessive genes in the tomato plant produce an absence of anthocyanin pigment (a), hairless plants (h), and jointless fruit stems (j). In a testcross involving a trihybrid F1, 3,000 progeny were scored. If the observed recombination frequency between anthocyaninless and jointless is 20%, what is the genetic distance between these two genes?

Accepted Answer

$$20\ 	ext{cM}$$

Question 2

In a three-point testcross in corn, the following progeny numbers were observed: abc (70), a b c (44), b c (95), a c (41), a b (288), b (288). What is the correct gene order?

Accepted Answer

b-c-a

Question 3

A tomato plant heterozygous for three linked genes is testcrossed. If the coefficient of coincidence is $$0.2$$, what is the interference?

Accepted Answer

$$0.8$$

Question 4

In a complementation test, two true-breeding Drosophila mutants with black body color are crossed. The F1 has wild-type color. What does this result indicate?

Accepted Answer

The mutations are in different genes

Question 5

Eight Drosophila mutants are tested for complementation and form three complementation groups. How many genes are likely involved?

Accepted Answer

3

Question 6

In a Sanger sequencing experiment, the following gel results are obtained (from top to bottom): G, T, A, C, G. What is the sequence of the newly synthesized strand?

Accepted Answer

5'-GTACG-3'

Question 7

A replication bubble diagram shows strands X and Y. If X is leading and Y is lagging, which direction is DNA synthesis occurring on each strand?

Accepted Answer

X: 5' to 3', Y: 5' to 3'

Question 8

If the observed double crossover frequency in a three-point testcross is $$0.02$$ and the expected frequency is $$0.05$$, what is the coefficient of coincidence?

Accepted Answer

$$0.4$$

Question 9

Given a coefficient of coincidence of $$0.4$$, what is the interference?

Accepted Answer

$$0.6$$

Question 10

In a three-point testcross, the recombination frequency between genes a and b is $$0.15$$, and between b and c is $$0.10. $$What is the expected frequency of double crossovers?

Accepted Answer

$$0.015$$

Question 11

A tomato plant is heterozygous for three linked genes. If the observed number of double crossovers is less than expected, what does this indicate about interference?

Accepted Answer

Interference is present

Question 12

In a three-point testcross, the gene order is determined to be b-c-a. If the recombination frequency between b and c is $$0.10$$ and between c and a is $$0.20$$, what is the total map distance between b and a?

Accepted Answer

$$0.30$$

Question 13

A plant is heterozygous for three linked genes. If the observed number of double crossovers is $$10$$ and the expected is $$25$$, what is the coefficient of coincidence?

Accepted Answer

$$0.4$$

Question 14

In a complementation test, two mutants fail to complement each other. What does this suggest?

Accepted Answer

Mutations are in the same gene

Question 15

In a Sanger sequencing gel, the bands from top to bottom are: T, C, A, G, C. What is the sequence of the newly synthesized strand?

Accepted Answer

5'-TCAGC-3'

Question 16

If the interference in a three-point testcross is $$0.5$$, what percentage of expected double crossovers is actually observed?

Accepted Answer

$$50\%$$

Question 17

A tomato plant is heterozygous for three linked genes. If the recombination frequency between a and b is $$0.10$$ and between b and c is $$0.20$$, but the observed double crossover frequency is $$0.01$$, what is the coefficient of coincidence?

Accepted Answer

$$0.33$$

Question 18

In a three-point testcross, if the gene order is a-b-c and the recombination frequencies are $$0.15$$ between a and b, and $$0.10$$ between b and c, what is the expected frequency of double crossovers?

Accepted Answer

$$0.015$$

Question 19

A replication bubble diagram shows four strands: W, X, Y, Z. If W and Y are leading, and X and Z are lagging, which of the following is correct?

Accepted Answer

W and Y are synthesized continuously; X and Z are synthesized discontinuously

Question 20

In a complementation table, eight mutants form four complementation groups. How many genes are likely involved?

Accepted Answer

4

Genetic Linkage, Mapping, Complementation, and DNA Replication: Study Notes

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