Meiosis crossover

Large segment deletion (unequal crossover in meiosis) Loss of fimrtion shorter than normal or entirely missing... 

Linked genes are likely to be inherited together because they are dose together on the same chromosome. Crossovers that occur between two linked loci during meiosis can produce a recombination of alleles. The frequency of recombination gives a measure of the distance between two genes. 

Frameshift mutations may be produced by various mechanisms. For instance, intercalation of planar molecules, such as acridine within the DNA molecule, allows base insertions at replication. Acridine-type compounds may also induce mutations of the frameshift type by interfering with the excision and repair processes, which correct errors occurring during unequal crossover between homologous chromosomes at meiosis. Such unequal crossover gives rise to errors of the frameshift type. 

Figure 6.45 Crossover at meiosis. Two homologous chromosomes are shown aligned in the top line. Each consists of two chromatids, joined together at the centromere. A and B represent genes on one chromosome, and a and b the corresponding alleles on the other chromosome. After recombination two new gene combinations are apparent. The middle and bottom lines represent other possible methods of recombination. Source From Refs. 12 and 13.

Egel-Mitani M, Olson LW, Egel R Meiosis in Aspergillus nidulans Another example for lacking synaptonemal complexes in the absence of crossover interference. Hereditas 1982 97 179-187. 

Centimorgan A measure of genetic distance that tells how far apart physically two genes are, based on the frequency of recombination or crossover between the two gene loci. A frequency of 1% recombination in meiosis is 1 centimorgan and equals about 1 million base pairs. See Southern, E.M., Rrospects for a... 

In S. cerevisiae, recombination (crossing over) between chromatids of homologous parental chromatids and cohesln cross-links between chromatids distal to the crossover are responsible for synapsis of homologous chromosomes during prophase and metaphase of meiosis I. A specialized cohesln subunit, Rec8, replaces the Sccl cohesln subunit during meiosis. 

Fig. 16.7 Meiosis in a diploid formed by a hypothetical cross aB x Ab. It is assumed that the genes A and B reside on the same chromosome (i.e. are linked). For simplicity only the relevant homologous pair of chromosomes is shown, (a) No genetic exchange occurs, (b) Genetic exchange - a single crossover between A and B. (See text and legend to Fig. 16.6 for further details.)...

Figure 2.1 Diagram for postulated mechanism of gene duplication with mispairing of the IgG H chain genes followed by an intercistronic crossover at meiosis giving rise to two IgGl genes, one with GF and another with (From Natvig et al, 1971.)...

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