The question
Name: ______________________ Date: ____________ Recombination frequencies and gene order (4 points)
Data table
Testcrosses for pairs of fruit fly genes
A researcher studied five genes in fruit flies, labeled V, W, X, Y and Z. For each pair of genes, she crossed females heterozygous for both genes, whose alleles came in known combinations from their parents, with males homozygous recessive for both genes. She then counted the offspring with recombinant (nonparental) combinations.
| Gene pair | Recombinant offspring | Total offspring | Recombination frequency (%) |
|---|---|---|---|
| W and X | 90 | 1,000 | 9.0 |
| X and Y | 130 | 1,000 | 13.0 |
| W and Y | 220 | 1,000 | 22.0 |
| W and Z | 70 | 500 | ? |
| W and V | 248 | 500 | 49.6 |
(a) Calculate the recombination frequency for genes W and Z. [1 point]
(b) Identify the order of genes W, X and Y on the chromosome, and support your answer with data from the table. [1 point]
(c) Explain what the recombination frequency of 49.6% for genes W and V indicates about where V is located. [1 point]
(d) Gene Z lies between X and Y. Predict the recombination frequency between genes X and Z, and justify your prediction. [1 point]