AQA GCSE Biology: Inheritance, variation and evolution — Practice Questions & Answers
How genetic information is passed from parents to offspring through reproduction, how variation arises, and how species change over time by natural selection, including DNA, inheritance, genetic technologies, evolution and classification.
1754 practice questions available for this topic — here are 10 with full answers and explanations.
WhyMeiosis produces gametes (sex cells). It halves the chromosome number, producing four genetically different haploid cells. Mitosis is used for growth, repair and asexual reproduction.
2Multiple choice · Easy
What is the term for an allele that is only expressed in the phenotype when two copies are present?
Dominant
Recessive
Heterozygous
Codominant
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WhyA recessive allele is only expressed when the organism is homozygous recessive (two copies). A dominant allele is expressed when at least one copy is present.
3Multiple choice · Easy
In humans, which pair of sex chromosomes determines a male?
XX
XY
YY
XO
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WhyMales have the sex chromosomes XY and females have XX. Eggs always carry X; sperm carry either X or Y, so the father's gamete determines the sex of the offspring.
4Multiple choice · Easy
Which of these is an example of asexual reproduction?
Bacteria dividing by binary fission
Fertilisation of an egg by a sperm
Pollen fertilising an ovule
Two parents producing seeds
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WhyAsexual reproduction involves only one parent and no fusion of gametes, producing genetically identical offspring (clones). Bacteria dividing by binary fission is asexual. The others involve gamete fusion.
5Multiple choice · Easy
What is the genetic material that carries the instructions for making an organism called?
DNA
ATP
Glucose
Protein
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WhyDNA (deoxyribonucleic acid) carries the genetic instructions. It is contained in chromosomes found in the nucleus of cells and is a polymer made of two strands forming a double helix.
6Multiple choice · Easy
Variation caused only by the conditions an organism lives in is described as:
Genetic variation
Environmental variation
Mutational variation
Continuous variation
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WhyEnvironmental variation is caused by external conditions (e.g. diet, climate, accidents) and is not inherited. Genetic variation is caused by differences in alleles inherited from parents.
7Multiple choice · Medium
A pea plant heterozygous for tall (T) is crossed with a homozygous short (t) plant. What ratio of tall to short offspring is expected?
3 tall : 1 short
1 tall : 1 short
All tall
1 tall : 3 short
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WhyTt x tt gives genotypes Tt, Tt, tt, tt. T is dominant, so Tt is tall and tt is short. This produces a 1:1 ratio of tall to short offspring (a test cross).
8Multiple choice · Medium
Which statement about cystic fibrosis is correct?
It is caused by a dominant allele
It is caused by a recessive allele
It only affects males
It is caused by an environmental factor
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WhyCystic fibrosis is caused by a recessive allele, so a person must inherit two copies (one from each parent) to have the disorder. Carriers have one allele but no symptoms. Polydactyly, by contrast, is dominant.
9Multiple choice · Medium
During meiosis, how many daughter cells are produced from one parent cell, and what is their chromosome content?
Two cells, each diploid
Four cells, each haploid
Four cells, each diploid
Two cells, each haploid
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WhyMeiosis produces four daughter cells, each genetically different and haploid (containing half the original chromosome number). This is essential so that fertilisation restores the full diploid number.
10Multiple choice · Medium
Which process introduces a useful gene from one organism into the genome of another?
Selective breeding
Genetic engineering
Natural selection
Tissue culture
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WhyGenetic engineering involves modifying the genome of an organism by inserting a gene from another organism, often using a vector such as a plasmid or virus. Selective breeding only uses genes already present in a species.
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Sexual reproduction: The production of offspring by the fusion of two gametes from different parents. It mixes genetic information from both parents, so the offspring are genetically different from each other and from their parents.
Asexual reproduction: The production of offspring from a single parent without the joining of gametes. Only mitosis is involved, so all the offspring are genetically identical clones of the parent.
Gamete: A specialised sex cell, such as a sperm or egg in animals or pollen and egg cells in plants, that contains only one copy of each chromosome.
Fertilisation: The joining of the nucleus of a male gamete with the nucleus of a female gamete, restoring the full number of chromosomes in the new cell.
Meiosis: A type of cell division that produces gametes. One parent cell divides twice to form four genetically different cells, each with half the normal number of chromosomes.
Mitosis: A type of cell division that produces two genetically identical cells, each with the full number of chromosomes. It is used in growth, repair and asexual reproduction.
Zygote: The single cell formed when a male gamete fuses with a female gamete at fertilisation, carrying the full chromosome number.
Clone: An organism that is genetically identical to its parent or to another organism, usually produced by asexual reproduction or cloning techniques.