AQA GCSE Biology

Genetics & inheritance

AQA GCSE Biology revision on Genetics & inheritance. Aligned to the AQA GCSE Biology 8461 specification. This bank has 25 practice questions on this topic.

Sample questions (3 of 25)

  1. Question 1

    How many chromosomes does a normal human body cell contain?

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    Answer: 46

    Humans are diploid - each body cell carries 46 chromosomes in 23 pairs. One of each pair comes from each parent. Sex cells (sperm, egg) are haploid: just 23 chromosomes.

  2. Question 2

    Which of these represents a dominant allele in genetics notation?

    • A) b
    • B) Aa
    • C) B
    • D) tt
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    Answer: B

    Convention: dominant alleles use capital letters (B, T), recessive use lowercase (b, t). A heterozygous organism has one of each (Bb) and the dominant trait is expressed. Homozygous = both alleles the same (BB or bb).

  3. Question 3

    DNA is contained in structures called...

    • A) Chromosomes
    • B) Ribosomes
    • C) Cytoplasm
    • D) Vacuoles
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    Answer: Chromosomes

    DNA is a long double-helix molecule. When a cell prepares to divide, the DNA condenses into thick visible CHROMOSOMES. A GENE is a section of DNA that codes for one protein. The whole DNA in one cell = the GENOME. Humans have ~20,000 genes spread across 23 chromosome pairs.

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