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Flashcards about X-linked traits, recombination, and gene mapping.
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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).
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.
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.
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.
What is gene mapping?
The process of determining the location of genes on a chromosome and the relative distances between them.
How is gene mapping done?
Using recombination frequencies to indicate how often crossing over occurs between two genes during meiosis.
What is recombination?
When two chromatids of a tetrad crossover at random points and swap genetic material.
What is recombination frequency?
The proportion of recombinant gametes out of the total gametes.
What are recombinant gametes?
Individuals that have new combinations of traits found in neither parent.
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.
What recombination frequencies do distant (unlinked) genes have?
Around 50%
What recombination frequencies do close (linked) genes have?
Between 0-50%
What is the relationship between distance and recombination frequency?
There is a near linear relationship between distance and recombination frequency.