Linkage Genes that are physically located on the

Linkage Genes that are physically located on the same chromosome are said to be “linked”. Linked genes are said to be “mapped” to the same chromosome. When two genes are mapped to the same chromosome, the genes will not assort independently during meiosis.

Linked alleles tend to be inherited together. Refer to Figure 4 -2, Griffiths et al. , 2015.

Crossing over produces new allelic combinations. Refer to Figure 4 -3, Griffiths et al. , 2015.

Chiasmata are the sites of crossing over. Also refer to Figure 4 -4, Griffiths et al. , 2015.

Crossing over is between chromatids, not chromosomes. Refer to Figure 4 -5, Griffiths et al. , 2015.

Multiple crossovers can include more than two chromatids. Refer to Figure 4 -6, Griffiths et al. , 2015.

Recombinants are produced by crossovers. Refer to Figure 4 -7, Griffiths et al. , 2015.

Independent assortment produces 50% recombinants. Refer to Figure 3 -13, Griffiths et al. , 2015.

For linked genes, recombinant frequencies are less than 50%. Refer to Figure 4 -8, Griffiths et al. , 2015.

Map distances are generally additive. Refer to Figure 4 -9, Griffiths et al. , 2015.

Longer regions have more crossovers and thus higher recombinant frequencies. Refer to Figure 4 -10, Griffiths et al. , 2015.