Linkage, Recombination And Eukaryotic Mapping Flashcards
What happens during recombination?
Alleles sort into new combinations.
What is the principle of segrgation?
Alleles separate during meiosis.
What is the principle of independent assortment?
Alleles at one locus sort independently from alleles at another locus.
Linked genes segregate together and crossing over produces ___ between them.
Linked genes segregate together and crossing over produces RECOMBINATION between them.
What does complete linkage lead to?
Nonrecombinant gametes and nonrecombinant progeny.
What does crossing over with linked genes lead to?
Recombinant gametes and recombinant progeny.
Becaue genes are carried on chromosomes, this creates a physical connection between genes that are close together on a chromosome. What is the term for this phenomenon?
Linkage.
It can be used to create a genetic map of gene position on chromosomes.
What is linkage disequilibirum?
The non-random association of alleles at different loci, which can be the result of close location of genes on a chromosome.
What is linkage disequilibrium influenced by?
Selection
The rate the recombination
The rate of mutation
Genetic drift
System of mating
Population structure
Genetic linkage.
For single crossovers, the frequency of recombinant gametes is half the frequency of crossing over because:
Each crossover takes place between only two of the four chromatids of a homologous pair.
How is recombination frequency calculated?
Recombination frequency = (# recombinant progeny/total # of progeny) x 100%
What occurs during coupling?
Wild type alleles are found on one chromosome; mutant alleles are found on the other chromosome.
True or false: linked genes segregate together.
True
What occurs during coupling?
One chromosome contains both wild-type alleles, one chromosome contains both mutant alleles.
What occurs during repulsion?
Wild type alleles and mutant alleles are found on the same chromosome.
What does recombination frequency allow us to do?
Recombination frequency allows us to predict expected offspring for a cross with linked genes.
The following testcross produces the progeny shown: AaBb x aabb -> 10 AaBb, 40 aaBb, 40 aaBb, 10 aabb. What is the percent recombination betwen the A and B loci? Were the genes in AaBb parent in coupleing or repulsion?
Percent recombination 20%; genes in AaBb parent is in repulsion.
What are genetics maps determined by?
Recombinant frequency.
A two-strand double crossover between two linked genes produces only what?
Nonrecombinant gametes.
How does a single crossover affect chromosomes?
It switches the alleles on homologous chromosomes.
A second crossover will reverse the effects of the first, restoring the original parental combination of alleles and producing only nonrecombinant genotypes in the gametes, althought parts on the chromosomes have recombined.
Recombinant chromosomes resulting from the double crossover have only the ___ gene altered.
Middle
A three-point testcross is carried out between three linked genes. The resulting nonrecombinant progeny are s+r+c+ and src, and the double cross over progen are s r c+ and s+r+c. Which is the middle locus?
C
What is the coefficient of coincidence?
The number of observed double cross/number of expected double crossovers.
What is interference?
1n - coefficient of coincidence.
