Q: If the recombination frequency between gene A and gene B is $$0.15$$ and between gene B and gene C is $$0.10$$, what is the expected frequency of double crossovers between A and C?

$$0.15 \times 0.10 = 0.015 or$$ $$1.5\%$$

Question 1

Which of the following best describes syntenic genes?

Accepted Answer

Genes located on the same chromosome

Question 2

In a dihybrid test cross involving two linked genes, which of the following outcomes would indicate genetic linkage rather than independent assortment?

Accepted Answer

Parental gamete types are produced at a frequency greater than 50%

Question 3

Which phase of meiosis is responsible for the crossing over that leads to genetic recombination between linked genes?

Accepted Answer

Prophase I

Question 4

If two genes are 10 map units apart, what percentage of gametes produced by a heterozygote will be recombinant for these genes?

Accepted Answer

$$10\%$$

Question 5

A test cross between a dihybrid plant (AaBb) and aabb produces the following offspring: 450 AaBb, 450 aabb, 50 Aabb, 50 aaBb. What is the recombination frequency between the A and B genes?

Accepted Answer

$$\frac{50+50}{1000} = 0.10 or$$ $$10\%$$

Question 6

Which of the following statements about genetic linkage is FALSE?

Accepted Answer

Linked genes always assort independently

Question 7

In a three-point test cross, which class of progeny is expected to be the least frequent?

Accepted Answer

Double-crossover types

Question 8

If the recombination frequency between gene A and gene B is $$0.15$$ and between gene B and gene C is $$0.10$$, what is the expected frequency of double crossovers between A and C?

Accepted Answer

$$0.15 	imes 0.10 = 0.015 or$$ $$1.5\%$$

Question 9

Which of the following best explains why recombination frequencies underestimate the true physical distance between two genes when they are far apart?

Accepted Answer

Double crossovers between the genes are not detected

Question 10

A geneticist observes that the number of double crossovers in a three-point test cross is much lower than expected. What is the term for this phenomenon, and how is it calculated?

Accepted Answer

Interference; $$I = 1 - c$$, where $$c is $$the coefficient of coincidence

Question 11

In a three-point test cross, the observed number of double crossovers is 6, and the expected number is 15. What is the coefficient of coincidence?

Accepted Answer

$$c = \frac{6}{15} = 0.4$$

Question 12

Which of the following is a real-world example that provided cytological evidence for crossing over being the physical basis of recombination?

Accepted Answer

Creighton and McClintock's experiments with chromosome 9 in corn

Question 13

A trihybrid test cross produces the following progeny numbers: 368, 368, 70, 74, 50, 50, 4, 2. Which two classes represent the double crossover progeny?

Accepted Answer

4 and 2

Question 14

If the recombination frequency between two genes is $$0.20$$, what is the expected proportion of parental gametes in the offspring?

Accepted Answer

$$1 - 0.20 = 0.80 or$$ $$80\%$$

Question 15

Which of the following statements about complete genetic linkage is TRUE?

Accepted Answer

No crossing over occurs between the linked genes

Question 16

In a three-point test cross, how can you determine which gene is in the middle?

Accepted Answer

Compare the parental and double-crossover progeny; the gene that differs is in the middle

Question 17

A geneticist performs a chi-square test on the results of a dihybrid cross and obtains a p-value less than 0.005. What does this indicate about the genes under study?

Accepted Answer

There is a significant deviation from independent assortment, suggesting genetic linkage

Question 18

Which of the following is the correct formula for calculating recombination frequency ($$r) $$between two genes?

Accepted Answer

$$r = \frac{	ext{number of recombinant progeny}}{	ext{total number of progeny}}$$

Genetic Linkage and Mapping in Eukaryotes: Study Notes

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드