Diploid & haploid number

Name the sub-cellular structure which stores the genetic material in an animal cell.

Complete the sentences to describe the genetic material.

Use words from the list.

diploid genes genome genotype

haploid heterozygous homozygous variation

The entire genetic material of an organism is called the........

Human body cells have 23 pairs of chromosomes because they have two copies of each

chromosome. These cells are called........

Human gametes have only 23 chromosomes. These cells are called........

Most observable characteristics are the result of multiple........

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.

The kangaroo diploid chromosome number is 16.

Which row shows the number of chromosomes found in each type of cell?

Complete Table 13.1 by choosing words from this list to identify the genetic term used to describe cell A and cell B.

diploid genotype haploid phenotype

Give an explanation for each choice of word in Table 13.1.

Huntington’s disease can cause death.

Fig. 13.3 shows the occurrence of HD by age when symptoms first appear.

What is the modal age range for the data shown in Fig. 13.3 ?

Early studies in the UK showed one in 15 000 have the HD allele. There are 66 000 000 people in the UK.

Calculate the number of people in the UK with the HD allele.

Read the information about HD in the box.

• The HD allele is a dominant allele that can lead to death.

• Alleles that cause death rarely persist in populations.

• About 10% of people with HD acquire the HD allele from a newly formed mutation and not through inheriting it from their parents.

Use this information and the data in Fig. 13.3 to suggest why the HD allele still persists in the human population.

Which word describes the number of chromosomes in a human sperm cell?

A Diploid

B Dominant

C Haploid

D Recessive

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.