Chromosomal Aberrations

Study Notes

Chromosomal aberrations can delete, add, or rearrange parts of one or more chromosomes, including deletions and duplications of genes or chromosome segments, and rearrangements of genetic material.
These structural changes occur due to one or more breaks along the axis of a chromosome, followed by loss or rearrangement of genetic material.
Chromosomes can break spontaneously, but the rate of breakage increases in cells exposed to chemicals or radiation.
The ends produced at points of breakage are "sticky" and can rejoin other broken ends.

Exchanges and transfers of genetic material between chromosomes are called translocations, altering the locations of genes within the genome.

Telomeres, the actual ends of chromosomes, do not readily fuse with newly created ends of "broken" chromosomes or with other telomeres.

If an aberration occurs in one homolog but not the other, the individual is heterozygous for the aberration, resulting in characteristic pairing configurations during meiotic synapsis.

Cri du Chat Syndrome (CdCS) is a genetic disease resulting from a deletion of the short arm of chromosome 5 (5p-).
Clinical features include a high-pitched cat-like cry, distinct facial dysmorphism, microcephaly, and severe psychomotor and mental retardation.
The size of the deletion ranges from the entire short arm to the region 5p15.

Gene redundancy occurs when multiple copies of genes code for specific RNA sequences, demonstrated through molecular hybridization.
In Escherichia coli (E. coli), about 0.7% of the haploid genome consists of rDNA, equivalent to seven copies of the gene.

Molecular hybridization is a process in which two complementary single-stranded DNA and/or RNA molecules bond together to form a double-stranded molecule.
This process is dependent on appropriate base-pairing across the two single-stranded molecules and is important in various research and clinical laboratory techniques.