Sex Linkage
In humans, there are 23 pairs of homologous chromosomes. 22 pairs are called autosomes and there is a pair of sex chromosomes. Females have two X chromosomes and males have two Y chromosomes. The Y chromosome has few genes. All mammals would develop as females in the absence of the genes on the Y chromosome which stimulate primary sexual development in the embryo.

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Key terms in this lesson
- Allele
- One of the different forms of a gene, arising from mutation, that occupies the same locus on homologous chromosomes.
- Linkage
- The tendency of genes located close together on the same chromosome to be inherited together rather than assorting independently.
More in Genetics and Variation
- Body Mass
- Genetic Variation
- Continuous and Discontinuous Variation
- Genetic Cross
- Dihybrid Crosses
- Linkage
- Χ-squared Test
- Epistasis
All 36 lessons in Genetics and Variation · All OCR A-level Biology topics