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Genetic terms and common inherited disorders

Inheritance, variation and evolution • Reproduction

Key concepts

What you'll likely be quizzed about

  • Gametes are sex cells, such as sperm and ova, that contain one set of chromosomes (haploid) produced during meiosis.
  • During fertilisation, gametes fuse to form a diploid zygote, restoring the normal chromosome number.
  • Gametes carry only one allele per gene, making dominant or recessive interactions observable only after fertilisation.

Flashcards

Test your knowledge with interactive flashcards

What does dominant mean in genetics?

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A dominant allele manifests its trait when at least one copy is present and is usually denoted by a capital letter.

Key notes

Important points to keep in mind

Gametes are haploid; fertilisation restores the diploid chromosome number.

Alleles are versions of the same gene; two alleles usually determine single-gene traits.

Dominant alleles express with one copy; recessive alleles express only with two.

Heterozygotes can transmit recessive alleles without expressing them.

Genotype = allele letters; phenotype = observable trait in descriptive terms.

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