Q: Which formula is used to calculate the genetic distance between two genes? $\text{Map units (cM)} = \frac{\text{Number of recombinants}}{\text{Total progeny}} \times 100$

$\text{Map units (cM)} = \frac{\text{Number of recombinants}}{\text{Total progeny}} \times 100$

Question 1

In a dihybrid cross between Drosophila with red eyes and normal wings (PR+, VG+) and those with purple eyes and short wings (pr, vg), what is the expected phenotypic ratio in the F2 generation if the genes assort independently?

Accepted Answer

1:1:1:1

Question 2

If the recombination frequency between the pr and vg genes in Drosophila is 11%, what is the genetic distance between these genes in centimorgans (cM)?

$	ext{Genetic distance (cM)} = 	ext{Recombination frequency} 	imes 100$

Accepted Answer

$11\ 	ext{cM}$

Question 3

Which of the following best describes genetic linkage?

Accepted Answer

Genes located close together on the same chromosome tend to be inherited together

Question 4

A cross yields 165 purple vestigial, 191 red normal, 23 purple normal, and 21 red vestigial offspring out of 400 total. What is the recombination frequency?

$	ext{Recombination frequency} = \frac{	ext{Number of recombinants}}{	ext{Total progeny}} 	imes 100$

Accepted Answer

$11\%$

Question 5

If two genes are 50 map units apart, how do they behave genetically?

Accepted Answer

They behave as if they are unlinked

Question 6

Which type of human genetic study is considered the gold standard for isolating a single variable?

Accepted Answer

Randomized Controlled Trials

Question 7

What is a major challenge in applying Mendel/Morgan’s methodology to human genetic studies?

Accepted Answer

Humans have long generation times and ethical constraints

Question 8

Which of the following is NOT a type of polymorphism used in genetic mapping?

Accepted Answer

Gene duplication

Question 9

In a population, marker alleles appear together in individuals with a disease more often than expected by chance. This phenomenon is called:

Accepted Answer

Linkage disequilibrium

Question 10

A pedigree analysis is most useful for which of the following purposes?

Accepted Answer

Determining the inheritance pattern of a mutation

Question 11

If a cross-sectional study is used to identify genetic risk factors for a disease, what is a major limitation?

Accepted Answer

It does not account for differing histories among individuals

Question 12

Which formula is used to calculate the genetic distance between two genes?

$	ext{Map units (cM)} = \frac{	ext{Number of recombinants}}{	ext{Total progeny}} 	imes 100$

Accepted Answer

$	ext{Map units (cM)} = \frac{	ext{Number of recombinants}}{	ext{Total progeny}} 	imes 100$

Question 13

Which of the following statements about crossing over is TRUE?

Accepted Answer

Crossing over is not always random and can occur at hotspots and cool spots

Question 14

Which type of polymorphism is defined as a genetic variation in repeat length?

Accepted Answer

Microsatellite markers (SSLP/STR)

Question 15

If you have 400 progeny and the genes are 50 cM apart, how many recombinant offspring would you expect?

$	ext{Number of recombinants} = 	ext{Total progeny} 	imes \frac{	ext{cM}}{100}$

Accepted Answer

$200$

Question 16

Which of the following is a reason why longitudinal studies are challenging in human genetics?

Accepted Answer

They are expensive and require following individuals over long periods

Question 17

Which of the following best describes a Single Nucleotide Polymorphism (SNP)?

Accepted Answer

A genetic variation at a single nucleotide position

Question 18

Why are polymorphisms useful in mapping the location of a mutation causing disease?

Accepted Answer

They serve as unique landmarks in the genome that can be tracked through generations

Question 19

Which of the following is a con of using natural experiments/case-studies (pedigrees) in human genetics?

Accepted Answer

Small sample sizes and unreliable verbal histories

Question 20

If two genes are very close together on a chromosome (1 cM apart), what is the probability that their alleles will NOT be inherited together?

Accepted Answer

$1\%$

Genetic Linkage- Sep 22

Study Guide - Practice Questions

Study Guide - Flashcards