5 Curly wings is a dominant mutation in the second chromosom

5. Curly wings is a dominant mutation in the second chromosome of Drosophilamelanogaster. A Cy/+ female was irradiated with X-rays (which makeschromosome breaks), and crossed with normal males. The Cy/+ sons weremated individually with normal males. From one cross, the progeny were:

curly males  0

curly females  157

wildtype males 142

wildtype females 0

What is unusual about these results?

What abnormality in chromosome structure is the likely cause of these results?

Please explain in detail.

Solution

Curly allele in female is translocated to X chromosome because of irradiation

Translocation of the curly allele at the curly locus to the X chromosome is the chromosomal abnormality

When a female with Cy/+ is crossed with male of +/+, it produces Cy/+ and +/+ phenotype

When Cy/+ sons were mated individually with +/+ females, it produced only curly females and wildtype males.

Males have only one X chromosome.

So one male X with cy and other female normal X combines it gives only curly females because both are X.

And Y from male combines with normal female X it gives only wildtype male

.