Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes

Klug - Essentials of Genetics 10th Edition

Klug10th EditionEssentials of GeneticsISBN: 9780135588789당신이 사용하는 게 아니라요?교과서 변경

Klug 10th Edition

Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes

문제 7

7장, 문제 7

What is the proposed basis for positive interference?

검증된 단계별 안내

Understand that positive interference refers to the phenomenon where the occurrence of one crossover event during meiosis reduces the probability of another crossover occurring nearby on the same chromosome.

Recognize that the proposed basis for positive interference involves the physical and structural constraints of the chromosome during meiosis, particularly how the formation of one crossover influences the chromosomal environment.

Consider the role of the synaptonemal complex and the tension along the chromosome axis, which may limit the formation of additional crossovers in close proximity to an existing one.

Explore the hypothesis that crossover events trigger a signal or structural change that inhibits nearby crossover formation, ensuring crossovers are more evenly spaced along the chromosome.

Summarize that positive interference is thought to arise from mechanical and biochemical feedback mechanisms that regulate crossover distribution to maintain genetic stability and proper chromosome segregation.

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주요 개념

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Genetic Crossover

Genetic crossover is the process during meiosis where homologous chromosomes exchange segments, creating genetic diversity. This exchange occurs at points called chiasmata and is essential for proper chromosome segregation and variation in offspring.

Positive Interference

Positive interference refers to the phenomenon where the occurrence of one crossover event reduces the probability of another nearby crossover on the same chromosome. This ensures crossovers are more evenly spaced, preventing clustering and promoting accurate chromosome segregation.

Mechanistic Basis of Positive Interference

The proposed basis for positive interference involves structural changes in the chromosome or the synaptonemal complex after a crossover forms, which inhibits nearby crossover formation. This may involve mechanical stress relief or signaling pathways that regulate crossover distribution.

관련 실천

교과서 질문

What two essential criteria must be met in order to execute a successful mapping cross?

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교과서 질문

Why are double-crossover events expected less frequently than single-crossover events?

The genes dumpy (dp), clot (cl), and apterous (ap) are linked on chromosome II of Drosophila. In a series of two-point mapping crosses, the following genetic distances were determined. What is the sequence of the three genes?

dp–ap: 42

dp–cl: 3

ap–cl: 39

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교과서 질문

Explain why a 50 percent recovery of single-crossover products is the upper limit, even when crossing over always occurs between two linked genes?

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교과서 질문

Colored aleurone in the kernels of corn is due to the dominant allele R. The recessive allele r, when homozygous, produces colorless aleurone. The plant color (not the kernel color) is controlled by another gene with two alleles, Y and y. The dominant Y allele results in green color, whereas the homozygous presence of the recessive y allele causes the plant to appear yellow. In a testcross between a plant of unknown genotype and phenotype and a plant that is homozygous recessive for both traits, the following progeny were obtained:

colored, green: 88

colored, yellow: 12

colorless, green: 8

colorless, yellow: 92

Explain how these results were obtained by determining the exact genotype and phenotype of the unknown plant, including the precise arrangement of the alleles on the homologs.

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교과서 질문

Why does more crossing over occur between two distantly linked genes than between two genes that are very close together on the same chromosome?

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