A woman has XX sex chromosomes and a man has XY sex chromosomes. They already have three sons.
Which statement describes the probability that their next child will be a daughter?
It is 50%50\%50% because each fertilisation is independent.
It is 25%25\%25% because three sons have already been born.
It is 75%75\%75% because daughters must balance the sons.
It is 100%100\%100% because a daughter must follow three sons.
43 exam-style questions on Edexcel GCSE Biology 3.3 Inheritance, covering 3.3.1 Gregor Mendel and the basis of genetics, 3.3.2 Alleles and inherited characteristics, 3.3.3 Monohybrid inheritance, 3.3.4 Determination of sex at fertilisation, 3.3.5 Outcomes from monohybrid crosses, 3.3.6 Inheritance of ABO blood groups, 3.3.7 Inheritance of sex-linked disorders, and 3.3.8 Multiple genes and phenotypic features. Each one has a worked solution and a mark scheme showing where the marks go.