Linkage Flashcards
What is a parental type gamete?
A gamete with the same alleles as one of the parents in the parental generation, not the F1!
What is a recombinant type gamete?
A gamete with alleles that are a combination of the parents in the parental generation
How do we write the genotype for two genes if they are unlinked?
A/a;B/b
How do we write the genotype for two genes if they’re linked?
AB/ab
If two genes are unlinked, how many parental to recombinant type gametes will we get?
50% parental, 50% recombinant
If two genes are linked, how many parental to recombinant type gametes will we get?
> 50% parental, <50% recombinant
If two genes are completely linked, how many parental to recombinant type gametes will we get?
100%, no recombinants
What will be the phenotypic ratio observed in the F1 testcross progeny if two genes are unlinked?
1:1:1:1 - they are independently assorting
What will be the phenotypic ratio observed in the F1 testcross progeny if two genes are linked?
Not 1:1:1:1. The ratio depends on how close the genes are together
What will be the phenotypic ratio observed in the F1 testcross progeny if two genes are completely linked?
1:1. No recombinant progeny will be seen
Why can’t we get any recombinant progeny if two genes are completely linked?
The genes are so close together that there can’t be any crossing over between them.
What will be the phenotypic ratio observed in the F1 testcross progeny if two genes are more than 50 map units apart?
1:1:1:1. Genes that far apart assort independently because crossing over happens so often
How are recombinant type gametes generated when genes are unlinked?
Independent assortment, how the bivalents arrange themselves and how they are segregated during anaphase 1 of meiosis
How are recombinant type gametes generated when genes are linked?
From crossing over between them during prophase 1 of meiosis
What is the recombination frequency? How do we calculate it?
How often two genes recombine.
RF = # of recombinants/ total # of testcross progeny
