Lect 20 - X-linked traits and recombination

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Flashcards about X-linked traits, recombination, and gene mapping.

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13 Terms

1
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What are sex-linked traits?

Traits involving genes on the sex chromosomes (X/Y) rather than autosomes, leading to different inheritance patterns between males (XY) and females (XX).

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What is the inheritance pattern when an affected father has children with an unaffected mother for an X-linked trait?

The father transmits the mutant allele to all daughters but to no sons, as only the Y chromosome is inherited by sons.

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What is the inheritance pattern when an unaffected father has children with a carrier mother for an X-linked trait?

The carrier mother passes the mutation to half her sons and half her daughters; sons with the mutation will be affected, and daughters with the mutation will be carriers.

4
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What is the inheritance pattern when an affected father has children with a carrier mother for an X-linked trait?

There is a 50% chance that each child will be affected; daughters who do not have the trait will be carriers, and males without the trait will be free from the recessive allele.

5
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What is gene mapping?

The process of determining the location of genes on a chromosome and the relative distances between them.

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How is gene mapping done?

Using recombination frequencies to indicate how often crossing over occurs between two genes during meiosis.

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What is recombination?

When two chromatids of a tetrad crossover at random points and swap genetic material.

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What is recombination frequency?

The proportion of recombinant gametes out of the total gametes.

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What are recombinant gametes?

Individuals that have new combinations of traits found in neither parent.

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How does the distance between two genes relate to the likelihood of chiasmata forming?

The smaller the distance between two genes, the less likely chiasmata will be formed.

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What recombination frequencies do distant (unlinked) genes have?

Around 50%

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What recombination frequencies do close (linked) genes have?

Between 0-50%

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What is the relationship between distance and recombination frequency?

There is a near linear relationship between distance and recombination frequency.