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Recombination Frequencyand
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 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 – BBYYBrown with yellow fat - bbyy
• produces the dihybrid - BbYy 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:– BlackWhite125– BlackYellow75– BrownWhite85– BrownYellow115
• 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 - BBYYBrown with yellow fat - bbyy
• produces the dihybrid - BbYy • 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:– BlackWhite125– BlackYellow75– BrownWhite85– BrownYellow115
(75+85) / (125+115+75+85)
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, (BbFf) with rabbits that are brown, chinchilla (bbff). The following results were obtained:
o31 brown, chinchilla (bbff)o35 black, full (B-F-)o16 brown, fullo19 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:
o31 brown, chinchillao35 black, fullo16 brown, full o19 black, chinchilla
• map distance between the 2 genes
(16+19) / (31+35+16+19)
35/101
0.35 = 35%
35 map units
• 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:
• b – vg 17
• cn-vg 8
• b-cn 9
• 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
• 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