Q: How is map distance between two genes calculated using recombination frequency?

Map distance (in centimorgans) $$= \text{recombination frequency} \times 100$$

Question 1

A Drosophila fly has the genotype $$w^+w$$ for the white eye gene, where $$w^+ is $$wild type and $$w is a $$recessive mutation. What is the phenotype of this fly?

Accepted Answer

Red eyes

Question 2

Which of the following best describes gene linkage?

Accepted Answer

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

Question 3

If two genes are completely linked, what is the expected recombination frequency between them?

Accepted Answer

$$0\%$$

Question 4

A test cross is performed between a heterozygous Drosophila for two linked genes ($$AaBb) $$and a double recessive ($$aabb). If $$the genes are unlinked, what proportion of the offspring would you expect to be recombinant?

Accepted Answer

$$50\%$$

Question 5

Which of the following statements about recombination frequency is correct?

Accepted Answer

It can never exceed $$50\%$$ because at $$50\%$$ the genes assort independently

Question 6

How is map distance between two genes calculated using recombination frequency?

Accepted Answer

Map distance (in centimorgans) $$= 	ext{recombination frequency} 	imes 100$$

Question 7

A researcher observes that the recombination frequency between two genes is $$12\%. $$What is the map distance between these genes?

Accepted Answer

$$12$$ centimorgans

Question 8

Which of the following is an example of an anonymous genetic marker and its relevance?

Accepted Answer

Variable nucleotide tandem repeats (VNTRs), which can be used in forensic DNA fingerprinting

Question 9

Single nucleotide polymorphisms (SNPs) are important in genetic studies because:

Accepted Answer

They can serve as markers to track inheritance of nearby genes

Question 10

Huntington's disease is caused by which type of genetic mutation?

Accepted Answer

An expansion of CAG trinucleotide repeats in the HTT gene

Question 11

Which of the following is a potential new treatment approach for Huntington's disease?

Accepted Answer

Gene silencing using RNA interference to reduce mutant HTT expression

Question 12

Why is autism referred to as a spectral disorder?

Accepted Answer

Because it encompasses a wide range of symptoms and severities

Question 13

Which of the following is a characteristic of mutations found in individuals with autism spectrum disorder (ASD)?

Accepted Answer

They can be de novo mutations found in both fathers and mothers

Question 14

A Drosophila cross involves two genes, A and B, that are linked. If the parental genotypes are $$AB/ab$$ and $$ab/ab$$, and the recombination frequency is $$10\%$$, what percentage of the offspring will have recombinant genotypes?

Accepted Answer

$$10\%$$

Question 15

Which of the following best explains why the maximum recombination frequency between two genes is $$50\%$$?

Accepted Answer

Because at $$50\%$$ recombination, genes assort independently as if they are on different chromosomes

Question 16

A researcher is studying two traits in Drosophila and observes that the recombinant offspring increase as the distance between the two loci increases. What is the most likely explanation?

Accepted Answer

More recombination events occur as the physical distance between genes increases

Question 17

Which of the following is true about a test cross involving linked genes?

Accepted Answer

It can reveal the genotype of an individual by analyzing the phenotypes of the offspring

Question 18

A variable nucleotide tandem repeat (VNTR) is best described as:

Accepted Answer

A region of DNA where a short sequence is repeated a variable number of times

Question 19

Which of the following scenarios best illustrates the use of SNPs in studying a phenotype?

Accepted Answer

Identifying a SNP that is statistically associated with increased risk of type 2 diabetes in a population

Genetics: Linkage, Mapping, and Human Genetic Disorders

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