The Roles of Genes in Determining the Phenotype - exam practice

Scientists self-pollinated some pea plants that were heterozygous for the gene controlling height. They expected a 3 : 1 ratio of tall plants to short plants in the offspring.

1,046 plants grew in the next generation. 798 were tall and 248 were short.

What is a statistical test that could be used to determine if these numbers are significantly different from a 3 : 1 ratio?

A researcher carried out an investigation into patterns of inheritance using mice as a model organism and observed the coat colour of the mice.

• Coat colour is controlled by two alleles which are not sex linked.

• The allele for yellow coat colour (A) is dominant to the allele for normal (agouti) coat colour (a).

Heterozygous yellow mice were crossed with each other repeatedly and the offspring obtained are shown in the table below.

Which statement describes the correct way to analyse these results?

A couple have a child. Both parents are heterozygous for the cystic fibrosis allele.

What is the probability that the child will have cystic fibrosis?

In a genetic context, what is a carrier?

What does a chi-squared value higher than the critical value suggest about the null hypothesis?

What does an epistatic gene do?

Which term describes a characteristic that is determined by a gene located on a sex chromosome?

What kind of genetic cross examines the inheritance of two different genes?

What is the probability of a child having blood group AB if one parent is heterozygous for blood group A (I^AI^O) and the other is heterozygous for blood group B (I^BI^O)?

In human blood groups, which alleles are codominant?

What term describes alleles that are both expressed in the phenotype?

In a dihybrid cross, what is the phenotypic ratio for a cross between individuals both heterozygous for two genes (e.g., RrYy x RrYy)?

What is the expected phenotypic ratio in the F2 generation of a monohybrid cross between a homozygous dominant and a homozygous recessive individual?