In a breed of sheep, coat colour is determined by two independently assorting genes, W/w W/w\,W/w and B/bB/bB/b, which exhibit dominant epistasis. The dominant allele W W\,W suppresses all pigment production, resulting in a white coat. In homozygous recessive ww ww\,ww individuals, the dominant allele B B\,B produces a black coat, whereas the homozygous recessive genotype bb bb\,bb produces a brown coat.
A white sheep with the genotype WwBb WwBb\,WwBb is crossed with another white sheep with the genotype WwbbWwbbWwbb.
What is the expected percentage of offspring from this cross that will have a black coat?
12.5%12.5\%12.5%
25.0%25.0\%25.0%
37.5%37.5\%37.5%
50.0%50.0\%50.0%
97 exam-style questions on OCR GCSE Biology 5.1 Inheritance, covering 5.1.1 The genome, 5.1.2 Environment and phenotype, 5.1.3 Variants and mutations, 5.1.4 How genetic variants influence phenotype, 5.1.5 Asexual and sexual reproduction, 5.1.6 Haploid and diploid, 5.1.7 Meiotic cell division, 5.1.8 Single gene inheritance, 5.1.9 Predicting single gene crosses, 5.1.10 Sex determination, 5.1.11 Multiple gene inheritance, and 5.1.12 Development of our understanding of genetics. Each one has a worked solution and a mark scheme showing where the marks go.