Biol1107 Unit 4: Genetics 18)In C elegans worms, Sterile () is recessive to fert
ID: 302120 • Letter: B
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Biol1107 Unit 4: Genetics 18)In C elegans worms, Sterile () is recessive to fertile (F), uncoordinated (m) is recessive to normal movement (M), and old () is recessive to normal lifespan (L).You perform test crosses involving worms that are heterozygous for different combinations for two genes at a time. Sterile, normal move. - 450 Uncoord., fertile- 450 Sterile, uncoord.-50 Uncoord, normal life. -250 Sterile, normal life-250 Old, fertile-250 Sterile, old-250 Old, normal move250 Uncoord, old-250 Normal life, fertile 250 Normal move, fertile-50 Normal move, normal life. 250 a) Do any of the genes appear to be on the same chromosome? Why? b) For any linked genes, indicate which phenotypes are the recombinant phenotypes c) What is the distance between these genes? 19)The percentage pf crossing over between four linked genes (K, L, M, & N) is as follows: Between K & L: 15% Between N & L: 11% Between M & N: 8% Between K & N: 596 Between M & L: 3% Create a linkage map for these genes on the chromosome below 20)At the right, draw a pedigree for the following familyExplanation / Answer
18. A)In the first and third test cross, we see a ratio of 1:1:1:1 . In the second test cross however, the ratio is 9:9:1:1 which violates the standard ratio of the law of independent assortment. This means that there appears to be some linkage or that some genes appear to be on the same chromosome.
b) The sterile, normal movement and the fertile,uncoordinated are the parental phenotypes (not the recombinant phenotypes )as these genes stay together during crossover in meiosis due to linkage. For the rest of the two phenotypes(which is less common) the genes would have seperated during crossover and thus creating recombinant phenotypes which are- sterile, uncoordinated and normal movement,fertile
c) Distance between these genes is calculated using recombination frequency=
recombinants/total progeny X100 = 100/1000 X100= 10
Thus the distance between genes is 10 centimograns
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