1. Black wool sheep is due to a recessive allele b and white wool sheep due to dominant allele B. A white ram (male) is crossed to white ewe (female), both animals carrying the allele for black. They produce a white lamb that is then backcrossed to the female parent. What is the probability of the backcross offspring being black?
2. The shape of radishes may be long (SL SL), round (SLSR) or oval (SRSR). If long radishes are crossed to oval radishes and F1 then allowed to cross at random among themselves, what phenotypeic ratio is expected in the F2?
3. Plumage colour in mallard ducks is dependent upon a set of 3 alleles: MR for restricted mallard pattern, M for mallard and m for dusky mallard. The dominance hierarchy is MR>M>m. Determine the genotype and phenotype ratios expected in F1 from the following crosses: a) MRX MRX MR, b) MR MR X MR M, c) MR MX MR M, d) MRmXMm and e) MmXmm.
4. In Drosophila, ebony body colour is produced by a recessive gene a and wild type (gray) colour by its dominant allele a+. Vestigial wings by recessive gene vg and normal wing (wild type) by vg+. If wild type dihybrid flies are crossed and produce 272 progenies, how many of these are expected in each phenotype class?
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