AQA GCSE Biology contents

Unit 6 · Inheritance, Variation & Evolution

Genetic Inheritance

3 min read · part of the full Exam Guide

The terms

Term Meaning
Gamete a sex cell (sperm, egg, pollen) with half the chromosomes
Chromosome a long molecule of DNA carrying many genes
Gene a section of DNA coding for one protein (one characteristic)
Allele a different form of a gene; you have two alleles of each gene, one from each parent
Dominant an allele that is always expressed, even if only one copy is present (capital letter, B)
Recessive an allele expressed only if two copies are present, with no dominant allele (lower case, b)
Homozygous the two alleles are the same (BB or bb)
Heterozygous the two alleles are different (Bb)
Genotype the alleles present (BB, Bb, bb)
Phenotype the characteristic expressed (brown fur, black fur)
  • Some characteristics are controlled by a single gene: fur colour in mice, red-green colour blindness in humans. But most characteristics are controlled by multiple genes interacting

Full Exam Guide

The rest of this topic is in the full Exam Guide

The complete AQA GCSE Biology guide — every topic, exam checklist and common mistake — is coming soon. Until then, the first topic in every unit is free to read.

In the full topic

  • The terms
  • Genetic crosses
  • Inherited disorders
  • Sex determination
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