Question 1

Recombination analysis allows for the mapping of genes because the frequency of crossing over is proportional to what distance?

Accepted Answer

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Question 2

In a two-point test-cross analysis, what are the "two points" being tested?

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Question 3

In most tests of genetic linkage, the number of double crossovers is less than the number expected due to what effect, which limits the number of crossovers that can occur in a short length of chromosome?

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The answer of In most tests of genetic linkage, the...

Question 4

After analysis of 100 pedigrees, the Z_max from the analysis of linkage between a disease gene D and the DNA marker P was found to be 3.5 at θ = 0.25. Which of the following is the best interpretation of these results? A)No conclusion can be made regarding linkage of D and P. B)The evidence supports linkage of D and P at 25 cM. C)The evidence supports linkage of D and P at 2.5 cM. D)The evidence supports linkage of D and P at 0.25 cM. E)The evidence indicates that D and P are not linked.

Accepted Answer

The Z_max score of 3.5 indicates that there is evidence supporting linkage between the disease gene D and the DNA marker P. The value of θ at which this evidence was observed is 0.25, which corresponds to a distance of 25 cM between D and P on the chromosome. Therefore, the best interpretation of these results is that there is evidence supporting linkage of D and P at 25 cM.

Question 5

Incomplete genetic linkage is far more common than complete linkage. What is the term for gametes produced when recombination shuffles the alleles of linked genes?

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The answer of Incomplete genetic linkage is far more common...

Question 6

What organism exhibits complete genetic linkage, meaning there is no recombination between homologous chromosomes?

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Question 7

The Z_max from the analysis of a disease gene N and the DNA marker H was 2.5 at θ = 0.1. Which of the following is the best interpretation of this result? A)N and H are not linked. B)N and H are separated by 10 cM. C)N and H are separated by more than 10 cM. D)N and H are separated by less than 10 cM. E)No conclusion can be made regarding the linkage of N and H.

Accepted Answer

The answer of The Z_max from the analysis of a...

Question 8

Intragenic recombination can be detected __________.
A)based on recombination between homologs carrying different mutant alleles
B)by the recovery of 100% double-mutant chromosomes
C)by the recovery of both wild-type and double-mutant chromosomes
D)based on recombination between homologs with different mutant alleles and recovery of 100% double-mutant chromosomes
E)based on recombination between homologs with different mutant alleles and recovery of both wild-type and double-mutant chromosomes

Accepted Answer

Intragenic recombination occurs within a single gene on the same chromosome. It can be detected by the recovery of both wild-type and double-mutant chromosomes, as the result of recombination between homologs with different mutant alleles. Recovery of 100% double-mutant chromosomes alone would indicate that the mutants are in different genes or on different chromosomes. Recovery of both wild-type and double-mutant chromosomes indicates that intragenic recombination has occurred within the same gene on the same chromosome.

Question 9

Which type of crossover event produces two parental and two recombinant chromosomes in gametes?
A)single-strand crossover
B)two-strand double crossover
C)three-strand double crossover
D)four-strand double crossover
E)None of the above; all crossover events produce only recombinant chromosomes.

Accepted Answer

A three-strand double crossover involves two chromatids from homologous chromosomes crossing over twice, resulting in two parental and two recombinant chromosomes.

Question 10

There are three genes located in the gene order A-B-C on a chromosome. Would you expect the recombination frequency to be higher between A and B or A and C?

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The answer of There are three genes located in the...

Question 11

For a given haplotype, the frequencies of alleles for gene Y are Y = 0.65 and Y' = 0.35, and the frequencies at gene Z are Z = 0.25 and Z' = 0.75. What is the predicted frequency of the Y'Z' haplotype?
A)0.16
B)0.26
C)0.74
D)0.84
E)1.1

Accepted Answer

The answer of For a given haplotype, the frequencies of...

Question 12

What is observed when syntenic genes are close enough to one another that they are unable to assort independently?

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Question 13

Which type of crossover event produces all four recombinant chromosomes?
A)single-strand crossover
B)two-strand double crossover
C)three-strand double crossover
D)four-strand double crossover
E)None of the above; all crossover events produce a combination of parental and recombinant chromosomes.

Accepted Answer

A four-strand double crossover involves two homologous chromosomes each with double stranded breaks simultaneously migrating well beyond the normal pairing region. This creates two pairs of sister chromatids that eventually have to come back together again to form two functional chromosomes. The net result is two normal chromosomes, as well as two recombinant chromosomes, which have new combinations of maternal and paternal genes.

Question 14

What unit of physical distance between genes on a chromosome provides a convenient way to relate the recombination frequencies for linked genes with their positions and order along a chromosome?

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The answer of What unit of physical distance between genes...

Question 15

Refer to this map to answer the questions:  a)What is the distance between gene E and gene F?
b)Assuming I = 0, what is the probability of no crossovers between gene D and gene E?
c)Assuming I = 0, what is the probability of no crossovers between gene E and gene F?
d)Considering both gene pairs, what is the proportion of nonrecombinant gametes?
e)What is the predicted frequency of each parental gamete (DEF/def )?
f)What is the recombination frequency between gene D and gene E?
g)What is the recombination frequency between gene E and gene F?
h)What is the frequency of two single recombinant gametes between genes D and E?
i)What is the frequency of two single recombinant gametes between genes E and F?
j)What is the frequency of each of the double-recombinant gametes, DeF and dEf?
k)Fill in the blanks below to prove that the sum of the frequencies of the eight predicted gamete genotypes is equal to 1.0:
_______ + _______ + _______ + _______ + _______ + _______ + _______ + _______ = 1
DEF def Def dEF DEf deF DeF dEf

Accepted Answer

The answer of Refer to this map to answer the...

Question 16

When constructing a genetic map of Zea mays, Creighton and McClintock used genetic markers as well as structural differences in the homologous copies of chromosome 9 that can be seen under the microscope. What are these structural differences called?

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Question 17

What type of test would you use to determine the relative order of more than two genes?

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Question 18

Two genes, A and X, exhibit incomplete linkage. The frequency of each parental gamete (AX and ax)is 45%. What is the approximate frequency of the Ax gamete?

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The answer of Two genes, A and X, exhibit incomplete...

Question 19

Morgan realized that Bateson and Punnett had detected genetic linkage but they couldn't explain their results because they performed the wrong cross. What type of cross did Morgan use for the analysis of genetic linkage of autosomal genes in Drosophila?

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The answer of Morgan realized that Bateson and Punnett had...

Question 20

What is the term for chromosomes that do not reshuffle the alleles of linked genes?

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Quiz 5: Genetic Linkage and Mapping in Eukaryotes

Recombination analysis allows for the mapping of genes because the frequency of crossing over is proportional to what distance?

In a two-point test-cross analysis, what are the "two points" being tested?

In most tests of genetic linkage, the number of double crossovers is less than the number expected due to what effect, which limits the number of crossovers that can occur in a short length of chromosome?

After analysis of 100 pedigrees, the Zmax from the analysis of linkage between a disease gene D and the DNA marker P was found to be 3.5 at θ = 0.25. Which of the following is the best interpretation of these results?

Incomplete genetic linkage is far more common than complete linkage. What is the term for gametes produced when recombination shuffles the alleles of linked genes?

What organism exhibits complete genetic linkage, meaning there is no recombination between homologous chromosomes?

The Zmax from the analysis of a disease gene N and the DNA marker H was 2.5 at θ = 0.1. Which of the following is the best interpretation of this result?

Intragenic recombination can be detected __________.

Which type of crossover event produces two parental and two recombinant chromosomes in gametes?

There are three genes located in the gene order A-B-C on a chromosome. Would you expect the recombination frequency to be higher between A and B or A and C?

For a given haplotype, the frequencies of alleles for gene Y are Y = 0.65 and Y' = 0.35, and the frequencies at gene Z are Z = 0.25 and Z' = 0.75. What is the predicted frequency of the Y'Z' haplotype?