Chromosomal abnormalities

Lux Lennox
T. Max
Biology
February 9, 2015
Cri-du-chat Syndrome
Cri-du-chat syndrome gets its name from the French language meaning “cry of the cat.” It is called this because one of the symptoms is a high-pitched signature scream or cry that comes from infants with this syndrome. The cry comes from abnormal larynx development. Every chromosome has a p arm and a q arm that are attached at the centromere of the chromosome. P is the shorter arm and q is the longer arm. “Cri-du-chat syndrome is caused by a deletion of the end of the short (p) arm of chromosome 5.” (Genetics Home Reference) Most of the critical information deleted that is responsible for this syndrome is located in band 5p15.2. The abnormality is written as 5p-. The affect of the deletion means that there are multiple genes that are missing which results in the symptoms of the disease.
The deletion is caused by a break in the DNA that makes up the chromosome. This break usually happens in the developmental stages of a sperm or an egg cell, which is done through meiosis or mitosis. It is caused by unequal recombination of chromosomes when they are lined up at the metaphase plate. “If the pairs of chromosomes don’t line up correctly, or if the chromosome breaks aren’t repaired properly, the chromosomes can gain or lose pieces.” (Learn.Genetics) Once one of the gametes with a DNA break is fertilized, that child will develop Cri-du-chat syndrome. Chromosome 5 has about 900 genes, which are the instructions to build proteins. With cri-du-chat syndrome, and many other syndromes, the deletion of part of the chromosome would be like removing a segment of the instructions (genes). Through the development of babies without certain parts of instruction, abnormalities will occur.
The symptoms vary depending on how much of the chromosome is actually missing. The most common recorded symptoms are being small at birth, possible respiratory problems, and problems with larynx development. People with the…