Question

Please answer #22-24, explain & clearly indicate which # you are answering. Thank you in advance!
(Q22-24) A normal chromosome has the following gene sequence. The o indicates a centromere of this chromosome. Normal Chromosomes: AB o CDEFGH I o JKLMN Var.1: Var.2: Var 3: Var.4: AEDC o BFGH AB o CDEFH I o JNKLMN Io JMLKN and duplication is Deletion is Varl, Var 3 Varl, Var 2 Var3, Var 2 Var2, Var 3 Var4, Var 1 D) 23. and paracentric inversion is B) Pericentric inversion is Varl, Var 2 Varl, Var 3 Var3, Var 2 Varl, Var 4 Var4. Var 1 24. If two homologous chromosomes are present as heterozygotes, which chromosomal variation may produce dicentric (two-centromere) chromosomal variation through crossing-over during meiosis? A) Var1 D) Var2 Var3 Var4 none

Answer 1

22) option D

Deletion -is a mutation (a genetic aberration) in which a part of a chromosome or a sequence of DNA is left out during DNA replication.

In Var2 'G' is left out during replication

Duplication can be defined as any duplication of a region of DNA that contains a gene.

In Var3 'N' is dulpicated

23) D

Var 1 is pericentric and Var4 is paracentric

Inversions are of two types: paracentric and pericentric.

Paracentric inversions do not include the centromere and both breaks occur in one arm of the chromosome. Pericentric inversions include the centromere and there is a break point in each arm.

24) A Var 1

The dicentric aberrations arise when exchange takes place between the centromeric pieces of two broken chromosomes. That is during repair of DNA strand breaks, misrepair of two chromosomes and abnormal chromosome replication can lead to dicentric chromosomes