Inheritance and genetic crossesIB MYP Biology: Mind map

Exam questions on Inheritance and genetic crosses

1. A student in Nairobi studies inheritance in pea plants. The gene for height has two alleles: the allele for tall stems (T) is dominant and the allele for short stems (t) is recessive.
   Define the terms allele and dominant.2 marks
2. A breeder in Lisbon keeps guinea pigs. Black fur is controlled by a dominant allele (B) and white fur by a recessive allele (b). She has two heterozygous black guinea pigs and one white guinea pig.
   The breeder crosses a heterozygous black guinea pig with the white one. State the expected ratio of black to white offspring and the genotype of the black offspring.2 marks
3. Cystic fibrosis is an inherited disorder caused by a recessive allele (f). A healthy couple, Amara and Kwame, have a first child who has cystic fibrosis. Both parents carry one copy of the allele.
   Explain how two healthy parents can have a child with cystic fibrosis.3 marks