Aneuploidy

Date: 2015-10-07; view: 580.

Euploidy. Gamete and somatic cells containing multiples of the haploid number of chromosomes are called polyploids. There are triploid (3n), tetraploid (4n) and so on. Poliploids is much more common in plants than in animals. Poliploidy in people is absent.

Two forms of polyploidy there are: autopolyploidy and allopolyploidy. Autopolyploidy arises as a result of increase in number of chromosomes within the same biological species, but allopolyploidy arises in a case of doubling the chromosome number in a sterile hybrid of different species.

Chromosomal aberrations, or changes in the shape of chromosomes,are results of disorder meiosis as usually. They are of two types: intrachromosomal and interchromosomal.

Intrachromosomal aberrations are deletions, inversions and duplication.

Interchromosomal aberration is translocations.

Deletion occurs due to separation and loss of chromosome segment. The affected chromosome loses certain genes, and becomes shorter then normal.

Inversion.A segment of chromosome separates and rejoins in an inverted position. Inversion changes the sequence nitrogenous bases in the chromosome.

Translocation. A segment of chromosome breaks off and joins a nonhomologous chromosome. Both the affected chromosomes get modified. The donor suffers deletion. The recipient has an extra set of genes.

Duplication. A fragment of a chromosome separates and joins a homologous chromosome. Thus a region of the chromosome becomes duplicated.