1. Recombination Frequency and Gene Linkage Mapping

2. Linked vs. Unlinked Genes

3. Crossing Over

4. Crossover Frequency

5. Mapping Using Frequency

6. Mapping Gene Loci

7. Recombination frequency
(Recombinant offspring)
(Total offspring)

8. 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?

9. 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?
( ) / ( )
320/1873
0.171 = 17.1%

10. produces the dihybrid - BbYy Black with white fat
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 - 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

11. produces the dihybrid - BbYy
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 - 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) / ( )
160/400
0.40 = 40%

12. 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:
31 brown, chinchilla (bbff)
35 black, full (B-F-)
16 brown, full
19 black, chinchilla
Determine the map distance between the 2 genes.

13. 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:
31 brown, chinchilla
35 black, full
16 brown, full
19 black, chinchilla
map distance between the 2 genes
(16+19) / ( )
35/101
0.35 = 35%
35 map units

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

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

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

17. 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

18. 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