GCSE Biology Inheritance questions by topic

Define the inheritance terms.

1. (a)Allele.[1]
2. (b)Dominant allele.[1]
3. (c)Genotype.[1]
4. (d)Phenotype.[1]

Complete the XX × XY sex-determination cross.

1. (a)Complete all four offspring combinations.[2]
2. (b)State the probability of a male child.[1]
3. (c)Explain which parent determines the child’s sex.[1]

Polydactyly is caused by a dominant allele (P). A heterozygous affected person (Pp) has a child with an unaffected person (pp).

1. (a)Complete a Punnett square for this cross.[2]
2. (b)State the probability of an affected child.[2]

A family tree shows two unaffected parents with an affected son.

1. (a)Is the trait dominant or recessive?[1]
2. (b)Explain your answer.[2]

Define these inheritance terms.

1. (a)Allele.[1]
2. (b)Genotype.[1]
3. (c)Phenotype.[1]
4. (d)Give one example of variation caused only by the environment.[1]

Complete the sex-determination cross for a human couple (mother XX, father XY).

1. (a)Give the sex chromosomes in the mother’s egg cells.[1]
2. (b)Give the sex chromosomes in the father’s sperm cells.[1]
3. (c)Give the ratio of girls to boys expected.[1]
4. (d)State which gamete decides a baby’s sex.[1]

Two heterozygous tall pea plants (Tt × Tt) are crossed.

1. (a)Complete the Punnett square.[2]
2. (b)State the genotype ratio.[1]
3. (c)State the phenotype ratio and explain why Tt plants are tall.[3]

Evaluate embryo screening for inherited disorders.

1. (a)Present benefits, concerns and a judgement.[6]

A couple, both carriers of cystic fibrosis (Cc), plan to have a family of four children.

1. (a)State the probability that any one child has cystic fibrosis.[2]
2. (b)Explain why it is possible that none of their four children has the disorder.[3]

Explain how the work of Mendel laid the foundations of modern genetics.

1. (a)Describe what Mendel did and found.[3]
2. (b)Explain why recognition was delayed.[2]

A woman heterozygous for a recessive condition (Bb) has a child with an unaffected man who is also a carrier (Bb).

1. (a)List the genotypes of the couple’s possible children, with the ratio.[2]
2. (b)State the probability that their next child is unaffected.[1]
3. (c)State the probability that their next child is a carrier.[1]
4. (d)Explain why unaffected parents can produce an affected child.[1]

Two couples attend a genetics clinic. Both members of couple 1 are carriers of cystic fibrosis (Cc). Both members of couple 2 have cystic fibrosis (cc).

1. (a)Draw a cross for couple 1 and give the probability of an affected child.[2]
2. (b)Give the probability that a child of couple 1 is an unaffected carrier.[1]
3. (c)State the possible genotypes of couple 2’s children and the phenotype ratio.[2]
4. (d)Explain why couple 1 may be offered embryo screening.[1]

A family tree shows an affected father and an unaffected mother with four children: two affected and two unaffected.

1. (a)Deduce the inheritance and genotypes.[4]
2. (b)State the probability of the next child being affected.[2]

(Higher) A couple lose a child to cystic fibrosis and are referred for genetic counselling. Both are confirmed carriers (Cc).

1. (a)Explain the genetic situation and the probabilities for future children.[4]
2. (b)Describe how embryo screening could help and one ethical concern it raises.[2]

Two identical twins were separated at birth and raised in different countries. As adults they have different body masses.

1. (a)Explain the differences using genotype and environment.[6]

A genetics app claims to predict a baby’s exact eye colour, height and intelligence from parents’ genes. Evaluate this claim.

1. (a)Assess the genetics behind each prediction and reach a judgement.[6]

A zebra finch breeder keeps birds in outdoor aviaries. Finches raised in cold summers grow shorter wings than those in warm summers, though all come from the same breeding line.

1. (a)Explain the wing-length differences using genotype and environment.[3]
2. (b)State whether wing length here is mainly genetic or environmental, and why.[2]

Explain how two healthy parents can have a child with a recessive condition, and why two parents with that condition cannot have an unaffected child.

1. (a)Explain the healthy-parents case, using the cystic fibrosis alleles C and c.[3]
2. (b)Explain the affected-parents case (cc × cc).[2]
3. (c)State the probability that a child of two carriers is a non-carrier.[1]