Mendel crossed pure-breeding tall pea plants with pure-breeding short pea plants. All the offspring were tall. He then crossed these offspring and obtained both tall and short plants.
Which explanation accounts for the short plants reappearing?
The first-generation plants had lost every copy of the short allele.
The first-generation plants carried an unexpressed short allele.
The short allele formed only when the second cross took place.
The tall allele changed into the short allele in every gamete.
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.