University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

64

Pages:

2
Author:

Mariam A. A.

Chromosomal Mutation Definitions: • • • Chromosomal mutation: a chromosome rearrangement resulting in a change in chromosome structure in a change in chromosome structure or number Non-disjunction: The failure of homologous chromosomes to separate during either mitosis or meiosis Aneuploidy: The condition in a cell where the chromosome number is not multiple of the haploid Processes: Types of chromosomal rearrangement: • • • • Deletion: occurs when a chromosome breaks, and a section of chromosome is lost Duplication: occurs when a selection of chromosome is copied and added Inversion: occurs when a section of chromosome breaks free, reorients, and re-joins in the reverse order Translocation: occurs when a section of chromosome breaks off but re-joins a different, nonhomologous chromosome Chromosomal mutations occurs when a cell is undergoing cell division. It can also occur as a result of exposure ionising radiation and some chemical mutagens. Chromosome mutations occur by chromosome numbers. The chances are large enough to be observed through karyotype comparison. Causes: • • • Same as point mutation, BUT another additional cause is The only difference is that if chromosomal mutation occurs spontaneously, it won’t be occurring during DNA replication stage of mitosis and meiosis. Instead, it will occur during crossing over events in mitosis and meiosis High heat energy and viruses can also cause chromosomal mutation, encouraging the abnormal exchange of chromosomal sections. Effects: • • • • • Deletion chromosomal mutation involves the loss of a chromosome section. This means that any genes that are located in that loss section is now lost. Duplication chromosomal mutation is when a chromosome section is copied. Therefore, the gamete may inherit an extra copy of the genes that are located in that copied chromosome section. Inversion chromosomal mutation involves a chromosome section breaking off and recombining, in a reversed order, with the original chromosome. The effect is that the inversion of chromosome section can prevent crossing over from occurring. This would therefore lower genetic variation of the offspring that is formed from the gametes that inherited the mutated DNA sequence. Translocation chromosomal mutation results in one chromosome section separating from a chromosome and combining with a non-homologous chromosome. The effect of this is similar to either deletion or duplication as one chromosome will have less genes whereas the other chromosome will have extra genes. A gamete can inherit either one of the DNA mutated sequence which means that the offspring can either have less genes than normal or a duplicated copy of the genes. Down syndrome disease is one disease that is caused by chromosomal mutation where offspring has one extra copy of the chromosome 21. This is because, due to chromosomal mutation, the mutated chromosome 21 cannot be separated during meiosis so offspring has an extra chromosome 21 (total of 3 copies). Normal humans are diploid, so we only have two copies of each chromosomes.