Genes & alleles

Inheritance is passing genetic material from one generation to the next.

Which terms describe sex cells in humans?

Tick (✓) two boxes.

Peas develop inside pods.

Pea pods can be green or yellow.

A pea plant with green pods is crossed with a pea plant with yellow pods. All the pods on the new plant are green.

Complete the sentences about the pea pods.

Use words from the list.

dominant haploid heterozygous

homozygous recessive

The results of this cross show that the allele for green is........ and the

allele for yellow is........

The genotype of the new plant is Gg. This means it is........ for pod

colour.

The new plants with green pods are then crossed.

What is the probability that a plant from this cross will have yellow pods?

Complete the genetic diagram to explain your answer.

Genetic material is required for inheritance in eukaryotic and prokaryotic cells.

Compare the genetic material found in eukaryotic and prokaryotic cells.

Peas develop inside pods.

Pea pods are either green or yellow. The allele for green is dominant over the allele for yellow.

The table shows some information about three different pea pods.

Complete the table.

A gardener crosses a plant that has green pods with a plant that has yellow pods. The gardener thinks both these plants have a homozygous genotype.

The result is 15 new plants with green pods and 3 plants with yellow pods.

Show that the gardener’s green plant did not have a homozygous genotype by completing the two genetic diagrams.

Use letters G and g for the alleles.

If the green plant has a homozygous genotype:

If the green plant does not have a homozygous genotype:

The ratio the gardener achieved was 5 green to 1 yellow.

Suggest why this does not match either of the offspring ratios.

A gardener grows a species of plant that has either red or white flowers. The colour of the flowers is controlled by a single pair of alleles, R and r.

The gardener crosses a plant that is homozygous for red flowers with a plant that is homozygous for white flowers. The diagram shows the results.

Explain why the offspring in the diagram are all red.

The offspring are all heterozygous for flower colour.

What is meant by the term heterozygous ?

The gardener grows another species of plant that can produce flowers of five different colours.

The gardener counts the number of plants for each flower colour.

The graph shows their results.

The gardener counted 97 plants.

Calculate the percentage of these plants that have blue flowers.

Give your answer to the nearest whole number.

What evidence is there in the graph that flower colour is an example of discontinuous variation in this species?

The male gametes of a plant are called pollen.

The sentences in the text box are about pollen. There are two words in the sentences that are not correct.

Pollen cells are haploid. This means that the pollen cells of a plant have twice

the number of chromosomes as the leaf cells of the plant.

Pollen cells are formed by a type of cell division called mitosis.

A gardener grows a species of plant that has either red or white flowers. The colour of the flowers is controlled by a single pair of alleles, R and r.

The gardener crosses a plant that is homozygous for red flowers with a plant that is homozygous for white flowers. The diagram shows the results.

Explain why the offspring in the diagram are all red.

The offspring are all heterozygous for flower colour.

What is meant by the term heterozygous ?

The gardener crosses one of these offspring plants with a plant that is homozygous for white flowers.

Predict the probability that the next generation of plants will have white flowers.

Complete the genetic diagram to explain your answer.

The gardener grows another species of plant that can produce flowers of five different colours.

The gardener counts the number of plants for each flower colour.

The graph shows their results.

The gardener counted 97 plants.

Calculate the percentage of these plants that have blue flowers.

Give your answer to the nearest whole number.

What evidence is there in the graph that flower colour is an example of discontinuous variation in this species?

The male gametes of a plant are called pollen.

The sentences in the text box are about pollen. There are two words in the sentences that are not correct.

Pollen cells are haploid. This means that the pollen cells of a plant have twice

the number of chromosomes as the leaf cells of the plant.

Pollen cells are formed by a type of cell division called mitosis.

Which term is used to describe a pair of alleles that control a characteristic?

A Gamete

B Genome

C Genotype

D Phenotype

The diagram shows a genetic cross for seed shape in peas.

Which prediction about the offspring is most likely?

A All the offspring will be heterozygous for seed shape.

B All the offspring will be homozygous for seed shape.

C The ratio of heterozygous to homozygous offspring will be 1: 1.

D The ratio of heterozygous to homozygous offspring will be 3: 1.

Some forms of breast cancer are linked to specific mutated genes called BRCA.

BRCA is a dominant allele.

Inheriting the BRCA allele means in both males and females, the risk of developing breast cancer is affected. It does not mean a person has been diagnosed with cancer.

A male who is heterozygous for BRCA has children with a female who is homozygous recessive.

How are they affected by the BRCA allele?

Put ticks (✓) in the correct boxes.

What is the percentage probability of them having a child with an increased risk of developing breast cancer?

Use a labelled genetic diagram to explain your answer.

Use the letter B for the dominant BRCA allele.

The genetic cross shows how genes are passed from parents to offspring.

Which part of the genetic cross shows the gametes?

Which statement about alleles and genes is correct?

A Alleles are found in the cytoplasm, while genes are only found in the nucleus on the DNA.

B Allele is just another name for gene, they are both the same codes for a characteristic.

C Genes are sections of DNA that code for a characteristic, alleles are different forms of a gene.

D It is possible to have two different genes for a characteristic but only one allele.

Type 1 diabetes is a disorder caused by lack of insulin production in the pancreas. Type 1 diabetes has a genetic link.

In humans the haploid number of chromosomes is 23. Insulin is a hormone controlled by a single gene found on chromosome number 11.

How many chromosomes are there in a single human pancreas cell?

Some individuals have a copy of the gene that would cause diabetes but do not have the disorder.

Suggest a reason why.

Some people can inherit a rare condition called ADPKD that results in kidney disease.

The PKD1 gene provides instructions for making a protein called polycystin-1. Polycystin-1 controls kidney cell differentiation.

In ADPKD, polycystin-1 does not work properly.

What name is given to a change in the PKD1 gene that causes ADPKD?

Explain why the ADPKD version of polycystin-1 prevents the kidney working properly.

A pregnant woman is heterozygous for ADPKD. The baby’s father does not have ADPKD and is homozygous recessive.

ADPKD is caused by a dominant allele (D).

What is the probability of their baby having ADPKD?

Use a labelled genetic diagram to explain your answer.