Question

How can chromosomes be damaged?

Answer 1

Hint: The nucleus present inside the plant and animal cells consist of thread-like structures known as the chromosomes. Each chromosome comprises a protein as well as a DNA molecule. The genetic information contained in the DNA is passed on from the parents to the offspring.

Complete answer:
Chromosome breaking agents are sometimes also referred to as the chromosomal clastogens. The breaking down of chromosomes can occur via various physical, chemical or biological agents. Physical agents or clastogens include ultraviolet light, X-rays, sound waves, magnetic fields and cold shock while biological clastogens include protozoa, viruses or certain genes. However, certain alkylating agents and other chemical mutagens like base analogues, intercalating agents, nitrous oxide, etc.

Chromosome can be damaged in the following ways:
-Translocation: This type of damage occurs during the division phase. In this, one chromosome arm gets attached with the non-sister chromosome.
-Trisomy: Any error during the meiosis results in trisomy. It often occurs due to the translocation when the division progresses without proper separation of chromosomes.
-Deletion: It occurs at the time of synthesis of DNA molecules. It may occur naturally or under the influence of mutagens thus interfering with the genome synthesis.
-Inversion: This type of damage occurs during the prophase I of meiosis. It involves the inversion of a particular fragment in the sequence.
-Duplication: It also happens at the time of synthesis of DNA molecules. It involves the synthesis of the same DNA fragment in a repetitive manner through replication machinery.

Note: Insertions are also one of the common causes of chromosomal damage; however the extent of damage they cause is not clear. Also, the mitotic divisions are also involved in damaging the chromosomes which may lead to even complete loss of the chromosome set present in an organism.