Challenge Question
Section 7.5
Question 7.40
Transferrin is a blood protein that is encoded by the transferrin locus (Trf). In house mice, the two alleles at this locus (Trfa and Trfb) are codominant and encode three types of transferrin:
| Genotype | Phenotype |
|---|---|
| Trfa/Trfa | Trf-a |
| Trfa/Trfb | Trf-ab |
| Trfb/Trfb | Trf-b |
The dilution locus, found on the same chromosome, determines whether the color of a mouse is diluted or full; an allele for dilution (d) is recessive to an allele for full color (d+):
| Genotype | Phenotype |
|---|---|
| d+d+ | d+ (full color) |
| d+d | d+ (full color) |
| dd | d (dilution) |
Donald Shreffler conducted a series of crosses to determine the map distance between the tranferrin locus and the dilution locus (D. C. Shreffler. 1963. Journal of Heredity 54:127−129). The following table presents a series of crosses carried out by Shreffler and the progeny resulting from these crosses.
- a. Calculate the recombination frequency between the Trf and the d loci by using the pooled data from all the crosses.
- b. Which crosses represent recombination in male gamete formation and which crosses represent recombination in female gamete formation?
- c. On the basis of your answer to part b, calculate the frequency of recombination among male parents and female parents separately.
- d. Are the rates of recombination in males and females the same? If not, what might produce the difference?
A mouse with the dilution trait.[Montoliu L, Oetting WS, Bennett DC. Color Genes. 3/2010. European Society for Pigment Cell Research. (http://www.espcr.org/micemut) 03/2013.]
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