Question

What are chromosomal aberration? Explain any two types of structural aberration with reference to their types mechanism and biological significance.

Answer 1

A chromosome abnormality, disorder, anomaly, aberration, or mutation is a missing, extra, or irregular portion of chromosomalDNA.[1] It can be from an atypical number of chromosomes or a structural abnormality in one or more chromosomes. Chromosome mutation was formerly used in a strict sense to mean a change in a chromosomal segment, involving more than one gene.[2] The term "karyotype" refers to the full set of chromosomes from an individual; this can be compared to a "normal" karyotype for the species via genetic testing. A chromosome anomaly may be detected or confirmed in this manner. Chromosome anomalies usually occur when there is an error in cell divisionfollowing meiosis or mitosis. There are many types of chromosome anomalies. They can be organized into two basic groups, numerical and structural anomalies.

Answer 2

Answer:

Chromosomal aberrations:

(1) The structural, morphological change, which take place in chromosome due to rearrangement, is called chromosomal aberrations.

(2) The aberrations change the sequence of the genes. This causes variations. Chromosomal aberrations are mainly of following four types

• (i) Deletion: Loss of genes from chromosome.
• (ii) Duplication: Genes are repeated or doubled in number on chromosorne.
• (iii) Inversion : A paricular segment or chromosome is broken and gets reattached to the same chromosome in an inverted position due to 180 twist. There is no loss or gain of gene complement of the chromosome.
• (iv) Translocation: Transfer or transpostion of a part of chromosome or a set of genes to a non-homologous chromosome is called translocation. It is effected naturally by he transposons present in the cell.