Please help! Thanks! Genetics mapping assignment Due Monday, February 19, 2018 A
ID: 197413 • Letter: P
Question
Please help! Thanks!
Genetics mapping assignment Due Monday, February 19, 2018 A Drosophila experiment examining linkage of X-linked genes studied a recessive eye mutation (echinus), a recessive wing-vein mutation (crossveinless), and a recessive bristle mutation (scute). The wild type phenotypes are dominant. Wild-type females which are heterozygous for all three loci were crossed with males showing the recessive phenotype for all three traits. 20,765 progeny were produced from these crosses and the phenotypes of each are listed below. (For the fles with only one trait listed 8576 977 716 681 8808 6. Scute, crossveinless, echinus 4 1002 1. Echinus 2. Scute 3. Crossveinless 4. Echinus, scute 5. Scute, crossveinless 7. Echinus, crossveinless 8. Wild-type Determine the gene order for the three genes and identify which alleles were on which female parental chromosomes a. Calculate the recombination frequencies and map distance between each of the gene pairs. b. c. Determine the interference value for this cross. What does this interference value mean?Explanation / Answer
11
so the gene order will be BAC means A should be in the middle.
a) Gene order for the three genes A, B and C is BAC.
(Where A denotes eyes phenotype, B denotes Wing phenotype and C denotes Bristle phenotype).
BaC on one female parental chromosome and bAc on other chromosome.
b) To construct the map of these genes we can use the formulae
Distance between 2 genes = (Number of single crossover + Number of Double crossover) / (Total number of progeny) x 100%
For B to A distance = 977+ 1002+4+1 / 20765
= 0.095 x 100 = 9.5cM
For A to C distance = 681+716+1+4/20765
=0.067x100 = 6.7cM (centimorgan)
The linkge distance between B and A is 9.5cM and the linkage distance between A and C is 6.7cM.
c) Interference = 1-(Observed Double crossover/ expected double crossover)
= 1-(4+1) / (0.9) (0.6)(20765)
= 1-5 / 11213
= 0.9
Genotype and phenotype observed progeny aBC (echinus) 8576 (Parental) ABc (Scute) 977 (Single crossover between A and B) AbC (Crossveinless) 716 (Single crossover between A and C) aBc (echinus, scute) 681(Single crossover between A and C) Abc (Scute , crossveinless) 8808 (Parental) abc (scute , crossveinless,echinus) 4 (Double crossover) abC (echinus, crossveinless) 1002 (Single crossover between A and B) ABC (Wild type) 1 (Double crossover)