Inheritance · Paper 1 — Free Biology HL Practice Questions

In Drosophila, red eye colour (allele $X^R$) is dominant over white eye colour (allele $X^r$). A female of genotype $X^R X^r$ is crossed with a male of genotype $X^r Y$. What is the probability that a randomly selected male offspring has white eyes?

A pea plant heterozygous for both seed shape and seed colour ($RrYy$) is self-pollinated. Round ($R$) is dominant over wrinkled ($r$), and yellow ($Y$) is dominant over green ($y$). What fraction of the offspring is expected to have round, green seeds?

An F1 plant from a cross between true-breeding yellow round (YYRR) and true-breeding green wrinkled (yyrr) pea plants is crossed with a homozygous recessive (yyrr) plant. Assuming independent assortment, what is the expected phenotypic ratio offspring from this test cross?