Sec 4 Biology Inheritance topical questions

Define allele and genotype.

Distinguish genotype from phenotype, using one example.

Define mutation and name one factor that increases the rate of mutation.

State which parent determines the sex of a child and explain why in one sentence.

State the blood-group phenotypes of the genotypes IAIA and IAIB.

Complete a Punnett square for the cross Hh × Hh, state the genotype ratio, and give the phenotype ratio.

A 3 : 1 cross produced 40 offspring: 32 tall and 8 short. Calculate the percentage of tall offspring, compare it with the expected numbers, and explain the difference.

A father has blood group A with genotype IAIO and the mother blood group B with genotype IBIO. Complete a genetic diagram and state the possible blood groups of their children with the ratio.

Distinguish continuous from discontinuous variation, giving one example of each.

In rabbits, the allele B for black fur is dominant to b for white fur. A heterozygous black rabbit is crossed with a white rabbit. Complete a genetic diagram and state the genotype and phenotype ratios of the offspring.

Explain how a child with blood group O can be born to a group-A mother and a group-B father, but not to a homozygous IAIA father.

Explain how the spread of antibiotic resistance in bacteria illustrates natural selection.

Two parents are both heterozygous carriers of the recessive allele h for a condition (Hh × Hh). Complete a genetic diagram, state the probability that a child is affected, and calculate the probability that their two children are both affected.

Explain how natural selection produces change in a population over generations, writing your answer as a chain of events from variation to evolution.

Compare the mutations involved in sickle cell anaemia and Down syndrome, and explain why exposure to X-rays or chemical mutagens is dangerous for gamete-forming cells.

Draw a genetic diagram for the cross XX × XY, state the expected ratio of sexes, and calculate the probability of a family of four children all being girls. Explain why this probability does not change no matter how many boys or girls are born first.

A couple are both carriers (Hh) of a recessive condition. (a) State the probability that their first child is affected. (b) They already have three unaffected children — state the probability that their fourth child is affected, and explain your reasoning.

A heterozygote × heterozygote cross (Hh × Hh) is set up to produce 800 offspring. (a) State the expected number of tall plants. (b) The observed result is 585 tall and 215 short. Calculate the observed percentage of tall plants and compare it with the expected percentage, explaining the difference.