Question 1

Which chromosomal alteration is illustrated when a segment of a chromosome is removed, resulting in the loss of genetic material, as shown in panel (a) of the first image?

Accepted Answer

Deletion

Question 2

In the context of deletion mapping, what is pseudodominance?

Accepted Answer

A phenomenon where a recessive allele is expressed because the dominant allele is deleted from the homologous chromosome

Question 3

Refer to the second and third images. Why does the organism in the third image display the recessive phenotype?

Accepted Answer

The dominant allele is deleted, so only the recessive allele is expressed

Question 4

A Drosophila with genotype $$w^+/Df(1)wr^J1$$ shows white eyes, while $$w^+/Df(1)$$mal^3$$ shows red eyes. What does this indicate about the location of the white gene?

Accepted Answer

The white gene is located between the breakpoints 3A1 and 3C2

Question 5

Which of the following best describes the purpose of using deficiency lines in deletion mapping experiments?

Accepted Answer

To identify the chromosomal location of a gene by revealing recessive phenotypes

Question 6

In a deletion mapping experiment, a gene is mapped to region B because:

Accepted Answer

Deletions overlapping region B all result in the mutant phenotype

Question 7

Which chromosomal alteration involves the exchange of segments between two nonhomologous chromosomes, as shown in panel (e) of the first image?

Accepted Answer

Reciprocal translocation

Question 8

Why do classical mapping techniques like testcrosses and deletion mapping work best for single-gene traits?

Accepted Answer

Each gene produces a clear, discrete phenotype that can be scored

Question 9

A trihybrid testcross provides additional information compared to a dihybrid testcross by:

Accepted Answer

Revealing the order of three linked genes and the distances between them

Question 10

If a chromosomal segment BCD is flipped in orientation but remains in the same location, as shown in panel (c) of the first image, what type of chromosomal alteration has occurred?

Accepted Answer

Inversion

Question 11

In a deletion mapping experiment, you cross an organism with a recessive mutant phenotype to several deficiency lines. If only the offspring from crosses with deletions covering region C show the mutant phenotype, what can you conclude?

Accepted Answer

The gene is located in region C

Question 12

Which of the following is NOT a possible outcome of a chromosomal deletion?

Accepted Answer

Duplication of a chromosomal segment

Question 13

A nonreciprocal translocation, as shown in panel (d) of the first image, results in:

Accepted Answer

Movement of a segment from one chromosome to a nonhomologous chromosome without exchange

Question 14

If a Drosophila with genotype $$w^+/Df(1)$$mal^3$$ has red eyes, what does this indicate about the white gene?

Accepted Answer

The white gene is not deleted in this deficiency line

Question 15

Which mapping technique is best suited for identifying the chromosomal location of a gene responsible for a discrete, single-gene phenotype?

Accepted Answer

Deletion mapping

Question 16

In a deletion mapping experiment, if a deficiency line uncovers a recessive phenotype, what does this suggest about the gene of interest?

Accepted Answer

The gene is within the deleted region

Eukaryotic Gene Mapping: Classical and Deletion Mapping Approaches

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