BIOL 344 Lecture 19: Lecture 19
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You conduct a trihbybrid cross starting with a parental generation consisting of a female expressing the mutant condition for all three traits and a male that is wild type for all three traits. This cross produces 1000 F2 offspring. The following are phenotypes among the F2 offspring.
Whisker trait | spotted belly trait | green eye trait | # F2 offspring |
+ | + | + | 320 |
Whiskers | Spotted Belly | Green eyes | 335 |
+ | Spotted belly | + | 161 |
Whiskers | + | Green eyes | 158 |
Whiskers | Spotted belly | + | 12 |
+ | + | Greeny eyes | 9 |
Whiskers | + | + | 3 |
+ | Spotted belly | Greeny eyes | 2 |
1)Which of the three genes for these traits lies in between the other two?
2) What is the recombination frequency estimated from these data for the whiskers and spotted belly traits?
3) What is the recombination frequency estimated from these data for the whiskers and green eyes traits?
4)What is the chromosome interference value estimated from these data for this region of the chromosome?
Question 3 (6 pts). In hogs, colored hair (H) is completely dominant to colorless (h) and bent tails (B) are completely dominant to straight tails (b). There are no interlocus interactions. Penetrance and expressivity are 100%. The two loci are not sex-linked. The phenotypes and frequencies of progeny following testcrosses of hogs 1 and 2 to a double recessive genotype (hh bb) are listed in the table:
Phenotype | Testcross Progeny of hog 1 | Testcross Progeny of hog 2 |
colored, bent | 134 | 28 |
colored, straight | 11 | 335 |
colorless, bent | 12 | 358 |
colorless, straight | 143 | 30 |
TOTALS | 300 | 751 |
For testcross progeny of hog 1, what are the recombinant classes or recombinant phenotypes in the progeny?
For testcross progeny of hog 2, what are parental classes or parental phenotypes in the progeny?
For hog 2, are the recessive alleles in the cis or trans configuration?
(2 pts) How far apart (in cM) are the two gene loci on the genetic map? You can use data from progeny of hog 1 or hog 2. Show your work.
For hog 1, If the two loci were sorting or segregating independently, what fraction of the testcross progeny would you expect to have colored hair and straight tails