Q: Which equation correctly calculates the map distance between two genes based on recombination frequency?

$$\frac{\text{Number of recombinant offspring}}{\text{Total number of offspring}} \times 100$$

Q: A geneticist observes the following F2 offspring from a test cross: 321 gray long, 333 ebony short, 117 ebony long, 125 gray short. What is the recombination frequency between the two genes?

$$\frac{117 + 125}{321 + 333 + 117 + 125} \times 100 = 27\%$$

Question 1

Which stage of prophase I in meiosis is characterized by the formation of the synaptonemal complex and the occurrence of crossing over between homologous chromosomes?

Accepted Answer

Pachytene

Question 2

Bateson and Punnett observed a deviation from the expected 9:3:3:1 ratio in a dihybrid cross involving sweet peas. What genetic phenomenon best explains their results?

Accepted Answer

Gene linkage

Question 3

If two genes are located close together on the same chromosome, which of the following is most likely to occur?

Accepted Answer

They will be inherited together more often than not

Question 4

Which equation correctly calculates the map distance between two genes based on recombination frequency?

Accepted Answer

$$\frac{	ext{Number of recombinant offspring}}{	ext{Total number of offspring}} 	imes 100$$

Question 5

In a mapping cross between two genes that are 16 map units apart, how many recombinant offspring would you expect out of 500 total offspring?

Accepted Answer

80

Question 6

Morgan’s experiments with Drosophila showed that some combinations of traits were more common than others in the F2 generation. What was the main conclusion from these results?

Accepted Answer

Genes located on the same chromosome tend to be inherited together

Question 7

If the recombination frequency between two genes is 27%, what is the map distance between them?

Accepted Answer

27 map units

Question 8

Which of the following statements about genetic linkage is FALSE?

Accepted Answer

Linked genes are always inherited together without exception

Question 9

Why does the observed recombination frequency underestimate the actual physical distance between two genes as the distance increases?

Accepted Answer

Multiple crossovers can occur but are not detected as recombination events

Question 10

A geneticist observes the following F2 offspring from a test cross: 321 gray long, 333 ebony short, 117 ebony long, 125 gray short. What is the recombination frequency between the two genes?

Accepted Answer

$$\frac{117 + 125}{321 + 333 + 117 + 125} 	imes 100 = 27\%$$

Question 11

Which of the following best describes the effect of crossing over during meiosis?

Accepted Answer

It increases genetic diversity by creating new combinations of alleles

Question 12

If the recombination frequency between genes A and B is 20%, between B and C is 15%, and between A and C is 5%, what is the correct order and map distances of these genes?

Accepted Answer

A - 5 mu - C - 15 mu - B

Question 13

Which of the following is NOT a use of genetic maps?

Accepted Answer

Determining the exact nucleotide sequence of a gene

Question 14

Mitotic recombination is rare but can result in which of the following outcomes if it occurs early in embryonic development?

Accepted Answer

A patch of tissue with a genotype different from the rest of the organism

Question 15

If two genes are on separate chromosomes, what is the maximum recombination frequency that can be observed between them?

Accepted Answer

50%

Question 16

A person inherits one mutant allele (RB−) of the retinoblastoma gene. What event during cell division can lead to the development of retinoblastoma in this individual?

Accepted Answer

Loss of the remaining normal RB+ allele in a retinal cell

Question 17

Which of the following best explains why recombinant offspring are fewer in number than non-recombinant offspring in a test cross involving linked genes?

Accepted Answer

Crossing over between linked genes is less frequent than no crossing over

Question 18

Which of the following is true regarding synteny?

Accepted Answer

It refers to the physical linkage of genes on the same chromosome

Question 19

If the map distance between two genes is 12.3 map units, what is the probability of recombination between them?

Accepted Answer

0.123

Question 20

Which of the following scenarios would most likely result in independent assortment of two genes?

Accepted Answer

The genes are far apart on the same chromosome

CHAPTER 7- Linkage, Recombination, and Genetic Mapping

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