Q: Which equation correctly represents the calculation of recombination frequency between two genes?

$\text{Recombination Frequency} = \frac{\text{Number of Recombinant Offspring}}{\text{Total Number of Offspring}} \times 100\%$

Q: In a two-point testcross, you observe 80 parental and 20 recombinant offspring. What is the map distance between the two genes?

$\frac{20}{100} \times 100\% = 20\%$ (20 map units)

Question 1

Which of the following best describes the purpose of chromosome mapping in eukaryotes?

Accepted Answer

To determine the relative positions of genes on a chromosome

Question 2

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

Accepted Answer

They tend to be inherited together due to genetic linkage

Question 3

During meiosis I, homologous chromosomes exchange DNA segments. What is the result of this process?

Accepted Answer

Production of recombinant chromosomes with new allele combinations

Question 4

A geneticist observes that two traits in fruit flies (body color and wing shape) are usually inherited together. What does this suggest about the genes controlling these traits?

Accepted Answer

The genes are linked and located on the same chromosome

Question 5

Which equation correctly represents the calculation of recombination frequency between two genes?

Accepted Answer

$	ext{Recombination Frequency} = \frac{	ext{Number of Recombinant Offspring}}{	ext{Total Number of Offspring}} 	imes 100\%$

Question 6

If two genes are 10 map units apart on a chromosome, what percentage of gametes are expected to be recombinant for these genes?

Accepted Answer

10%

Question 7

In a testcross between a heterozygote for two linked genes (AaBb) and a homozygous recessive (aabb), which gamete types are expected to be most frequent if the genes are closely linked?

Accepted Answer

Parental types (AB and ab)

Question 8

Which of the following statements about map units (m.u.) is correct?

Accepted Answer

1 map unit equals 1% recombination frequency

Question 9

A mother is a carrier for an X-linked recessive condition ($X X^*$) and the father is normal ($XY$). What is the probability that their son will be affected?

Accepted Answer

50%

Question 10

Why are parental types usually more frequent than recombinant types in the offspring of a testcross involving linked genes?

Accepted Answer

Crossing over between closely linked genes is less likely, so parental combinations are more common

Question 11

Which of the following is a necessary condition for two genes to be considered linked?

Accepted Answer

They must be less than 50 map units apart on the same chromosome

Question 12

In a two-point testcross, you observe 80 parental and 20 recombinant offspring. What is the map distance between the two genes?

Accepted Answer

$\frac{20}{100} 	imes 100\% = 20\%$ (20 map units)

Question 13

Which of the following best explains why crossing over is less likely to occur between two genes that are close together on a chromosome?

Accepted Answer

There is less physical space for crossover events to occur

Question 14

A fruit fly with genotype $BbVgVg$ (black body, vestigial wings) is crossed with $bbVg^+Vg^+$ (brown body, normal wings). If the genes are completely linked, what phenotypes will appear in the offspring?

Accepted Answer

Only black body, vestigial wings and brown body, normal wings

Question 15

Which of the following scenarios would most likely result in a recombination frequency of approximately 50% between two genes?

Accepted Answer

The genes are on different chromosomes

Question 16

In a real-world medical scenario, why is it important to know if two disease-related genes are linked?

Accepted Answer

It helps predict the likelihood of both diseases being inherited together

Question 17

Which of the following is NOT a result of crossing over during meiosis?

Accepted Answer

Reduction in chromosome number

Question 18

If a geneticist wants to determine whether two loci are linked, which type of cross would be most informative?

Accepted Answer

A testcross between a heterozygote for both loci and a homozygous recessive

Question 19

Which of the following statements about genetic linkage is correct?

Accepted Answer

Linked genes can be separated by crossing over, resulting in recombinant gametes

Chromosome Mapping and Genetic Linkage in Eukaryotes

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