Chromosomal Mutations Flashcards
Mutations
changes to the genome of the cell
- Involve changes to the DNA sequence of genes
Chromosomal mutation arises due to:
- Change in chromosome number (e.g. 47 chromosomes in Down syndrome)
- Structural modification of chromosome (translocation, duplication, inversion, deletion)
Errors that cause change in chromosome number
- Non-disjunction occurs during meiosis I or II hence producing gametes with an incorrect number of chromosomes
- Failure of 2 homologous chromosomes of a pair to separate to the opposite poles at anaphase I OR failure of sister chromatids to separate at anaphase II
- If a normal gamete fertilizes a (abnormal) gamete with an extra chromosome, the result is a zygote with a total of 2n+1 chromosomes (=Aneuploidy: a condition in which an organism has 1 or a few chromosomes above or below the normal chromosome number) → put into context
result of numerical aberration
If the organism survives, it will have
- An abnormal karyotype (number and appearance of chromosomes in the nucleus of a eukaryotic cell)
- Probably a syndrome of disorders caused by the abnormal number of genes
Errors that cause change in structure of chromosomes
- Deletion
- Duplication
- Inversion
- Translocation
Deletion
Results from the breakage of a chromosome in which the genetic material is lost during cell division. Breakage of chromosome can happen anywhere on the chromosome
Duplication
A major mechanism where new genetic material is generated, resulting in extra genetic material
Inversion
Rearrangement of genes, where the broken segment is reversed and inserted back on to the same chromosome
Translocation
Abnormality caused due to the rearrangement of parts between non-homologous chromosomes. The piece of chromosome detaches from one of the chromosome and moves to a new position to another chromosome
