Share
Explore BrainMass

# Biology problem

2.) A line of Drosophila melanogaster with ebony body and sepia eyes (line A) is crossed to a line with tan body and red eyes (line B). The F1 are all tan-bodied, red-eyed, and normal-winged.

What proportion of gametes produced by line A have the dominant allele for both loci?_____________

What proportion of the gametes produced by the F1 have the dominant allele for both loci?_____________

An F1 female is crossed to a male from line A.

If 1000 offspring were scored for both characters, what number of offspring would be expected to have each of the four phenotypes (assuming no linkage)? List them below.

(See attached file for full problem description)

#### Solution Preview

Linkage Question and Chi-Square

===============================

A line of Drosophila melanogaster with ebony body and sepia eyes (line A) is crossed to a line with tan body and red eyes (line B). The F1 are all tan-bodied, red-eyed, and normal-winged.

Clearly, the tan body and red eyes are wild type (wt). "Wilt type" means normal. Therefore line B is a wt line and line A is the double mutant line. Considering that all the F1 resemble line B, we can conclude that the F1 are phenotypically wt.

We show the ebony body allele as "e" and the wt tan allele as "E." Likewise, we show the mutant sepia eyes as "s" and the wt red eyes as "S." Therefore, line A would be eess and line B would be EESS. All gametes produced by line A would be es and all gametes produced by line B would be ES. The genotype of the F1 would be EeSs.

What proportion of gametes produced by line A have the dominant allele for both loci? 0%

The gametes produced by the EeSs F1 would ...

\$2.19