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Linkage

Genes which are inherited together because they are on the same chromosome are called linked genes. When linked genes are not on the sex chromosomes this is called autosomal linkage. The closer the genes are the more likely they are to be inherited as one unit, and the less likely crossing over as chiasmata occurs between the two genes. Therefore there is no independent assortment or random segregation of the alleles.As a result of linkage, the genotypic and phenotypic ratios will be lower for recombinant offspring since the likelihood that independent assortment of the alleles is reduced. The recombination frequency is the amount of crossing over and is the number of recombinant offspring divided by the total number of offspring.

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Specification: OCR Biology A (H420), A-level, 6.1.2 Patterns of inheritance. Topic: Genetics and Variation.

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.

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