Chromosomal Aberrations

Chromosomal Aberrations

• 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.

Translocations

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

Telomeres

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

Heterozygous Aberrations

• 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

• 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

• 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

• 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.