GCSE Biology: Genes, Chromosomes, and Inheritance

Biology Quiz - Unit 2 - Genetics (Questions)

This GCSE Biology quiz explores genetics, from chromosomes and alleles to inherited characteristics. Test how you understand inheritance patterns, Punnett squares, and key terms in genetic diagrams.

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Fascinating Fact:

At fertilisation, the nuclei of the gametes fuse, restoring the full number of chromosomes and creating a unique combination of alleles.

In GCSE Biology, genetics explains how characteristics are inherited from parents to offspring. You will study chromosomes, genes, and alleles, and use genetic diagrams to predict possible outcomes of crosses.

Key Terms

Gene: A short section of DNA that codes for a protein and helps to determine a characteristic.
Allele: A different form of the same gene, such as an allele for brown eyes or an allele for blue eyes.
Chromosome: A long, coiled DNA molecule carrying many genes, found in the nucleus of cells.

Frequently Asked Questions (Click to see answers)

What is genetics in GCSE Biology?

In GCSE Biology, genetics is the study of how characteristics are passed from parents to offspring through genes on chromosomes, explaining inheritance patterns and variation.

How do you draw a simple genetic diagram for GCSE?

To draw a genetic diagram, write the parental genotypes, show the gametes, combine them in a Punnett square, then use the outcomes to work out genotype and phenotype ratios.

What is the difference between genotype and phenotype?

The genotype is the combination of alleles an organism has for a gene, while the phenotype is the observable characteristic that results, such as eye colour or blood group.

Try These Related Quizzes

What are alleles?

[ ]	Different forms of an organism
[ ]	Different forms of an animal
[ ]	Different forms of a gene
[ ]	Different forms of an enzyme

In humans, genes are found in...

[ ]	pairs
[ ]	threes
[ ]	singly
[ ]	fours

If the genes were Tt, this means that the alleles are...

[ ]	the same
[ ]	identical
[ ]	different
[ ]	increased

In a recessive condition, such as cystic fibrosis, how many copies of the abnormal allele are needed for the person to be a sufferer?

[ ]	One
[ ]	Three
[ ]	Two
[ ]	Four

For a condition such as Huntington's disease, how many parents need to be affected for the children to inherit this condition?

[ ]	One
[ ]	Two
[ ]	None
[ ]	Only the grandparents

What offspring ratio would you expect from two parents who are carriers - Tt crossed with Tt?

[ ]	2:1
[ ]	3:1
[ ]	4:1
[ ]	1:1

What is the name of the technique used to test a foetus for genetic disorders?

[ ]	Embryo screening
[ ]	IVF
[ ]	Cloning
[ ]	Stem cells

What is a carrier?

[ ]	A person who has the disease and always passes it on to their offspring
[ ]	A person who is unaffected by the disease but can pass on the gene
[ ]	A person unaffected and incapable of passing on the condition through their genes
[ ]	A person infected who can spread the disease through a droplet infection

Humans have two sex chromosomes. What are the ones in women known as?

[ ]	XY
[ ]	X0
[ ]	XX
[ ]	XXY

10.

Sperm cells carry which of the following chromosomes?

[ ]	Just an X chromosome
[ ]	Just a Y chromosome
[ ]	Neither X nor Y chromosomes
[ ]	Either X or Y chromosomes

You can find more about this topic by visiting BBC Bitesize - Genetics

Biology Quiz - Unit 2 - Genetics (Answers)

What are alleles?

[ ]	Different forms of an organism
[ ]	Different forms of an animal
[x]	Different forms of a gene
[ ]	Different forms of an enzyme

Alleles are given letters. A different letter of the alphabet is used for each gene. The dominant allele is given an upper case letter e.g. T and the recessive allele is given a lower case letter e.g. t

In humans, genes are found in...

[x]	pairs
[ ]	threes
[ ]	singly
[ ]	fours

Genes are always found in pairs. One of the pair was inherited from Mum and the other one of the pair of genes comes from Dad

If the genes were Tt, this means that the alleles are...

[ ]	the same
[ ]	identical
[x]	different
[ ]	increased

You can tell that by the fact that there is a capital letter and also a small letter - genetics are case sensitive!

In a recessive condition, such as cystic fibrosis, how many copies of the abnormal allele are needed for the person to be a sufferer?

[ ]	One
[ ]	Three
[x]	Two
[ ]	Four

Both parents need to be carriers for the child to inherit cystic fibrosis. Parents would be Cc and the child with cystic fibrosis would be cc

For a condition such as Huntington's disease, how many parents need to be affected for the children to inherit this condition?

[x]	One
[ ]	Two
[ ]	None
[ ]	Only the grandparents

Huntington's disease is a dominant condition so only one copy of the faulty gene is needed to cause it. Normally, it is only diagnosed in middle-aged people, which means that they have already passed it on to their children. There is a form that affects children but it is very rare

What offspring ratio would you expect from two parents who are carriers - Tt crossed with Tt?

[ ]	2:1
[x]	3:1
[ ]	4:1
[ ]	1:1

Only the offspring that receive the recessive genes from both parents will be unaffected by Huntington's disease

What is the name of the technique used to test a foetus for genetic disorders?

[x]	Embryo screening
[ ]	IVF
[ ]	Cloning
[ ]	Stem cells

Genetic tests are not available for all inherited diseases and sometimes they can give a false positive result

What is a carrier?

[ ]	A person who has the disease and always passes it on to their offspring
[x]	A person who is unaffected by the disease but can pass on the gene
[ ]	A person unaffected and incapable of passing on the condition through their genes
[ ]	A person infected who can spread the disease through a droplet infection

This most commonly occurs with recessive conditions