Chromosome Aberration slides

Lecture Book 4 PG 39

• 15(h) Describe mutation as a change in the structure of a gene such as in sickle cell anaemia, or in the chromosome number, such as the 47 chromosomes in the condition known as Down syndrome

• 2(d) Explain what is meant by the terms gene mutation and chromosomal aberration. For chromosomal aberration, knowledge of numerical aberration (including aneuploidy, as in the case of trisomy 21, i.e. Down syndrome) and structural aberration (including translocation, duplication, inversion and deletion) is required. PG 39

PG 39

• A change in the number or structure of chromosomes • Several gene loci are involved PG 39

• Errors in nuclear division in mitosis and meiosis: 1. Non-disjunction in mitosis or meiosis leads to a change in the number of chromosomes (Numerical aberration) Failure of one of more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, => Abnormal distribution of chromosomes in daughter nuclei PG 39

• Errors in nuclear division, i.e. in mitosis and meiosis: 2.Chromosomal breaks that occur during mitosis or meiosis resulting in deletion, duplication, inversion or translocation of chromosomal segments leads to a change in the structure of chromosome (Structural aberration) PG 39

PG 40

Caused by Non-disjunction Failure to separate anaphase in mitosis anaphase I in meiosis anaphase II in meiosis failure of sister chromatids to separate failure of homologous chromosomes to separate failure of chromatids* to separate during PG 40

Nondisjunction in Mitosis Not in notes