Question

Female Drosophila heterozygous for ebony (e +/e), scarlet (st+/st) and spineless ( ss+/ ss) were test crossed and the following progeny were obtained:
Progeny phenotypes Number
Wild type 67
Ebony 8
Ebony, scarlet 68
Ebony, spineless 347
Ebony, scarlet, spineless 78
Scarlet 368
Scarlet, spineless 10
Spineless 54

a) Are these genes linked? Justify your answer.
b) Write the genes given on a chromosome symbol with the genes in correct order.
c) Write the genotypes of the flies involved in parental cross and test cross.
d) What is the map distance between the loci for ebony and scarlet?
e) What is the map distance between the loci for ebony and spineless?
f) Calculate the coefficient of coincidence

Answer 1

Answer:

.

d) What is the map distance between the loci for ebony and scarlet?

e) What is the map distance between the loci for ebony and spineless?

f) Calculate the coefficient of coincidence

Answer 2

a) yes these genes are linked because the classes of parent give rise to other six types of classes as shown in recombination type linkage.

b) Genes given on chromosomes are: st-ss-e : scarlet, spineless and ebony.

c) The genotypes of the files inlvoved in cross: (female) st ++ * (male)st ss e

d) the map distance between eboni and scarlet :(67+78+68+54)/1000

e) the map distance between eboni and spineless: (67+54+10+8)/1000

f) coeficient of coincidence = 0.018/0.0228 = 0.7894