No Soacing Hg 2.0In Drosophila, Dichetae (D) is a chromosome 3 mutation with a d
ID: 206509 • Letter: N
Question
No Soacing Hg 2.0In Drosophila, Dichetae (D) is a chromosome 3 mutation with a dominant effect on wing shape. The heterozygote DD+ is viable, but homozygous DD is lethal. The genes striped thorax (sr) and sepia (se) are chromosome 3 recessive mutations affecting the thoracic stripes and eye colour respectively Flies from a Dichaete stock were crossed to homozygous stripe-body and sepia flies, and the F, females with a Dichaete phenotype were test crossed to the male parental stripe-body, sepia stock to produce the progeny listed in the table below est cross striped, Dichaete sepia Dichaete sepia striped Dichaete striped stripe Wild-type Total 320 | 320 100 100 65 15 15 1000 2.1 Are the genes for body colour, wing shape and eye colour assorting independently or linked? Explain your answer 2.2 If genes are linked, calculate the distances between them. 2.3 Calculate the interference and coincidence values 24 Give the genotypes of parental strains, F, and the test cross progeny 8 3Explanation / Answer
Question 2.1.
Answer. No , the genes for eyes color , wing shape and body color are not assorting independently instead they are linked because otherwise they would have produced progeny in 9:3:3:4.
Question 2.2
Answer.
Where SCO = Single cross over
DCO = Double cross over.
The gene order is " SE D+ SR ".
Distance betwwen SE and D+ = (No of SCO btw SE and D+) + (No. of DCO )/ Total X 100%
= 65+ 100+ 15+15 / 1000
= 19.5 cM
Similaerly,
Distance between SR and D+ = 65+100+15+15/ 1000 X 100%
= 19.5 cM
Therefore linkage map is
SE--------------------------19.5cM------------D+------------19.5cM----------------SR.
Question 2.3
Answer.
Interference = 1 - coefficient of coincidence
Coefficinet of Coincience(COC) = Observed double cross over / Expected double cross over X1000
= 15+15 / 0.195 X .195 X 1000
= 30/ 38
= 0.78
Interference = 1- COC
= 1- 0.78
= 0.22.
Question 2.4.
Answer. Please refer the table for genoytpes.
Please feel free to ask if anythong is not understood.
Phenotype Genotype Number Type of crossover Dichaete D+ SE SR 320 Parental Striped,Sepia D+ sr se 320 Parental Dichaete, Striped D+ sr SE 65 SCO btw SR and D+ Sepia D+ SR se 65 SCO btw SE and D+ Dichaete, Sepia D+ SR se 100 SCO btw SR and D+ Striped D+ sr SE 100 SCO btw SE and D+ Dichaete, Striped, Sepia D+ sr se 15 DCO Wild-type D+ SR SE 15 DCO Total 1000Related Questions
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