Inheritance

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........

Eye colour, height and weight in humans all show variation.

Which of these are examples of continuous variation?

A Eye colour and height

B Eye colour, height and weight

C Height and weight

D Height only

Two students want to see if the length of a pea pod affects the number of pea seeds inside the

They measure the length of pea pods in millimetres using a ruler. They open the pods and count the pea seeds inside.

What is the independent variable in their investigation?

Tick (✓) one box.

Write down two variables they need to control to make the data valid.

The students choose five pea pods with a length of between 45 – 55 mm and count the number of seeds inside each pod.

Look at their results.

Calculate the mean number of seeds.

Write your answer in the table.

Use your answer to part (b)(i) to calculate the length of pod per seed.

The students repeat the experiment for pea pods between 65 – 75 mm.

The mean number of seeds was 6.7 and length of pod per seed was 11.2 mm.

Write down two conclusions from this experiment.

How could the students make sure the samples they collect are representative?

The phenotype of peas is controlled by many factors.

Write down two environmental factors that could affect pea pod length.

Early genetic studies identified the colour of pea pods as green or yellow. Results suggested that the colour is an example of single gene inheritance.

Why is it not easy to work out the genotype of skin colour in humans?

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.