Chromosome IV in Drosophila is a very small chromosome and carries a tiny amount
ID: 203209 • Letter: C
Question
Chromosome IV in Drosophila is a very small chromosome and carries a tiny amount of genetic material. Fruit flies that are trisomic for chromosome IV have no apparent phenotypic abnormalities, andtheyretaintheirfertility. AmongthegenesonchromosomeIVisoneforwhicharecessivealleleey produces the “eyeless” phenotype. A male that is trisomic for chromosome IV and has the genotype + eyeyiscrossedtoadiploidheterozygousfemale. Assumingthatrandomsegregationofchromosomes takes place during spermatogenesis, and that all sperm are viable, what proportion of offspring will be trisomic and eyeless?
A. 1/12
B. 1/6
C. 1/4
D. 1/3
E. 1/2
Explanation / Answer
Option C is correct. Since out of four phenotype combination two will be trisomic and out of which one will carry dominat and one will carry recessive. Only trisomic reccesive are eyeless.