Using map data to predict the progeny of the cross a+b+/ab with ab/ab
Let f =the expected frequency of cross overs
| Description | genotype | P | f=.1 | N=1000 |
|
Parental type one |
a+ b+ | (1-f)/2 | .45 | 450 |
| Parental type two | a b | (1-f)/2 | .45 | 450 |
|
Recombinant |
a+ b | f/2 | .05 | 50 |
| Recombinant | a b+ | f/2 | .05 | 50 |
Example: If genes a and b are twenty map units apart (ie. f= .2) what is the expected progeny from a cross between an organism that is heterozygous for a and b is test crossed to an organism that is ab/ab. Assume that one parent was a+ b/a+ b. What is the probability that the double recessive will be found in the progeny?
| Description | genotype | P | f=.2 | N=1000 |
|
Parental type one |
a+ b | (1-f)/2 | .40 | 400 |
| Parental type two | a b+ | (1-f)/2 | .40 | 400 |
|
Recombinant |
a b | f/2 | .10 | 100 |
| Recombinant | a+ b+ | f/2 | .10 | 100 |
The answer is P = 0.10
How does this problem change for three linked loci?
by Kenneth G. Wilson,
Professor of Botany
Miami University
wilsonkg@muohio.edu