BRAINCAKEHomologous Chromosomes
Organisms that undergo sexual reproduction have one set of chromosomes contributed by each parent.
In humans, before fertilisation the egg cell has half the number of chromosomes and is said to be haploid. The sperm cell is also haploid and has the same number and type of chromosomes as the egg cell with the same genes in the same loci. Meiosis is a type of cell division that gives rise to haploid gametes.
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Key terms in this lesson
- gene
- A length of DNA that codes for a polypeptide or a functional RNA molecule, at a specific locus on a chromosome.
- allele
- One of the different versions of a gene, arising by mutation, that occupy the same locus on homologous chromosomes.
- meiosis
- A type of nuclear division that produces four genetically different haploid daughter cells (gametes) from a diploid parent cell.
More in DNA, Genes and Protein Synthesis
- Genes
- The Genetic Code
- Features of the Genetic Code
- Chromosomes
- Alleles
- The Human Karyotype
- Protein Synthesis
- RNA
All 15 lessons in DNA, Genes and Protein Synthesis · All AQA AS-level Biology topics