In Drosophila, the X-linked eye colors are tinged, ivory, eosin, apricot, wine a
ID: 37530 • Letter: I
Question
In Drosophila, the X-linked eye colors are tinged, ivory, eosin, apricot, wine and
blood are caused by a series of 6 alleles all of which are recessive to the seventh wildtype allele red,
but which produce intermediate phenotypes in all other heterozygotes. In other words, females
heterozygous for the allele determining red have red eyes, but females heterozygous for the alleles
determining tinged and ivory have an eye color that is intermediate to these two colors.
11. How many different hemizygous genotypes exist?
(a) six
(b) seven
(c) twelve
(d) fourteen
(e) twenty one
12. How many different homozygous genotypes exist?
(a) six
(b) seven
(c) twelve
(d) twenty one
(e) twenty two
13. How many different heterozygous genotypes exist?
(a) six
(b) seven
(c) twelve
(d) fourteen
(e) twenty one
Please explain your reasonings thank you in advance
Explanation / Answer
11. a is correct. This is because except the recessive wild type red allele all other can form hemizygous genotype with intermediate eye color.
12. b is correct. All the 7 alleles can result in forming the homozygous genotype.
13. e is correct. All 7 alleles can form heterozygous genotype with another type of allele as below.
tinged - ivory; tinged - eosin; tinged - apricot; tinged - wine; tinged - blood; tinged - red
ivory - eosin;ivory - apricot; ivory - wine; ivory - blood; ivory - red
eosin - apricot; eosin - wine; eosin - blood; eosin - red
apricot - wine; apricot - blood; apricot - red
wine - blood, wine - red
blood - red