Question

What causes an extra copy of a chromosomal region to occur?

Answer 1

ANSWER- Chromosomal duplication results in extra copy of a chromosomal region to occur.

Explanation- Various types of changes or mutations occur in chromosomes which are as follows-

• Duplication- In this, a stretch of chromosome is repeated or it can be said that an extra copy of chromosomal region is present in the chromosome. It generally occurs due to recombination between misaligned homologous chromosomes at the time of meiosis in germ cells which leads to the duplication of chromosomal region resulting in extra copy if that region in the chromosome. Duplication leads to increase in the size of chromosome.

• Inversion- In this, a stretch of chromosome is broken and then again join to the chromosome but in the reverse order (not similar to normal order). In this, chromosome size remains same.
• It is of two types- Pericentric inversion in which the centromere is involved in the process and Paracentric inversion in which the centromere is not involved and breaking of stretch occurs near centromere.

• Deletion- In this, a stretch of chromosome is deleted from the chromosome resultiong in shorter length of chromosome. Deletion occur during DNA replication when a stretch of DNA which is part of chromosome is not replicated.

• Translocation- In this ,a stretch of DNA breaks from one chromosome and attaches to another chromosome results in making one chromosome short and other chromosome longer in length. It is of two types-
• Simple translocation- In this ,a stretch of DNA breaks from one chromosome and attaches to another chromosome in the same manner as it was on previous chromosome.
• Reciprocal translocation- In this ,a stretch of DNA breaks from one chromosome and attaches to another chromosome in the reverse manner as it was on previous chromosome.

Our question is about extra copy of chromosomal region which occurs in duplication.