Recombination Frequency and Gene Linkage Mapping Linked vs

Recombination Frequency and Gene Linkage Mapping

Linked vs. Unlinked Genes

Crossing Over

Crossover Frequency

Mapping Using Frequency

Mapping Gene Loci

Recombination frequency (Recombinant offspring) (Total offspring)

• A wild-type fruit fly (heterozygous for gray body color and normal wings) was mated with a black fly with vestigial wings. The offspring has the following phenotypic distribution: • Wild type (gray-normal) 778 • Black-vestigial 785 • Black-normal 158 • Gray-vestigial 162 • What is the recombination frequency between these genes for body color and wing type?

• A wild-type fruit fly (heterozygous for gray body color and normal wings) was mated with a black fly with vestigial wings. The offspring has the following phenotypic distribution: • Wild type 778 • Black-vestigial 785 • Black normal 158 • Gray vestigial 162 • What is the recombination frequency between these genes for body color and wing type? (158+162) / (778+785+158+162) 320/1873 0. 171 = 17. 1%

• In rabbits the dominant allele B produces a black coat color and the recessive genotype bb produces a brown coat. • Body fat color in rabbits is white if a dominant allele Y is present and yellow if the genotype is yy. • Assume the mating between rabbits with the following genotypes : Black with white fat – BBYY Brown with yellow fat - bbyy • produces the dihybrid - Bb. Yy Black with white fat • Calculate the recombination frequency if the dihybrids are mated back to brown rabbits having yellow fat, bbyy, and the following ratio of phenotypes is observed: – – Black. White 125 Black. Yellow 75 Brown. White 85 Brown. Yellow 115

• In rabbits the dominant allele B produces a black coat color and the recessive genotype bb produces a brown coat. • Body fat color in rabbits is white if a dominant allele Y is present and yellow if the genotype is yy. • Assume the mating between rabbits with the following genotypes : Black with white fat - BBYY Brown with yellow fat - bbyy • produces the dihybrid - Bb. Yy • Calculate the recombination frequency if the dihybrids are mated back to brown rabbits having yellow fat, bbyy, and the following ratio of phenotypes is observed: – Black. White 125 (75+85) / (125+115+75+85) – Black. Yellow 75 – Brown. White 85 – Brown. Yellow 115 160/400 0. 40 = 40%

Question #1 • In rabbits, black (B) is dominant to brown (b), while full color (F) is dominant to chinchilla (f). The genes controlling these traits are linked. • The following cross was made: rabbits heterozygous for both traits that express black, full color, (Bb. Ff) with rabbits that are brown, chinchilla (bbff). The following results were obtained: o 31 brown, chinchilla (bbff) o 35 black, full (B-F-) o 16 brown, full o 19 black, chinchilla • Determine the map distance between the 2 genes.

Question #1 • In rabbits, black (B) is dominant to brown (b), while full color (F) is dominant to chinchilla (f). The genes controlling these traits are linked. • The following cross was made: rabbits heterozygous for both traits that express black, full color, with rabbits that are brown, chinchilla. The following results were obtained: (16+19) / (31+35+16+19) o 31 brown, chinchilla 35/101 o 35 black, full o 16 brown, full 0. 35 = 35% o 19 black, chinchilla 35 map units • Determine the map distance between the 2 genes

• Determine the sequence of genes along a chromosome based on the following recombination frequencies: • b – vg 17 • cn-vg 8 • b-cn 9

• Determine the sequence of genes along a chromosome based on the following recombination frequencies: • A-B 8 • A-C 28 • A-D 25 • B-C 20 • B-D 33