When white eyed and miniature winged Drosophila melanogaster is crossed with its wild type, it produces following percent of recombinants. A) 1.3% B) 37.2% C) 62.8% D) 98.7%
Correct option:(B)37.2%
Solution:
- Drosophila, when white eyed and miniature winged (wwmm) female is crossed with wild type, that is red eyed normal winged (w+w+m+m+) males, 62.8% of the progeny was of parental types .
- And only 37.2% were recombinants.
- Shows that linkage between genes for white body and miniature wing is loose linkage.
- So, recombinant occurs along with parental combinations in offsprings, this type of linkage is called as incomplete linkage.
9
• According to Mendel, the F2 phenotypic dihybrid ratio is 9:3:3:1.
• The ratios of Morgan’s dihybrid cross between white eyed, yellow bodied female Drosophila and red eyed, brown bodied male Drosophila was significantly different. It produced 1.3% recombinants and 98.7% progeny with parental type combinations.
• Morgan and his group knew that the genes were located on the X chromosome. Hence, they observed that when two genes in a dihybrid cross are located on the same chromosome, the proportion of parental gene is much higher than the non-parental gene.
• He also coined the terms linkage (the physical association of genes on a chromosome) and recombination(when crossing over of genes occurs). When linkage is very tight, recombination is lower and when linkage is very loose, recombination is higher.