Human Genetic Disorder - Abnormalies of Autosomes

Abnormalies of Autosomes

Edward’s syndrome

It occurs more often in females than males
Frequency: 1 per 8000 live births
Symptoms: Small jaws, deformed ears, small mouth, nose and fingers, small sternum and pelvis.

Patau’s Syndrome

13-Trisomy or D-Trisomy
The common anomalies of D-trisomy include hare-lip, cleft-palate, sloping forehead with relatively small head and brain and defective eye development.

Down Syndrome

First autosomal aneuploidy, described by John Longdon Down (1866) under the name of mongoloid idiocy or mongolism.
21-Trisomy
47 chromosomes instead of 46 with three copies of chromosome 21 instead of of usual two.
Karyotype: XXY (reason: Non-disjunction of chromosome of pair during meiosis)
The frequency of non-disjunction of chromosome pair 21 increases with mother age.
The frequency of abnormality is 1in 600 live births.
Clinical symptoms : Male with slowly degenerating testes, enlarged breasts.

Cri du syndrome (Cat cry syndrome)

The affected newborn cries like mewing of a cat, hence it is named a Cri du chat (cat cry)
Is due to a deletion in the short arm of the chromosome number 5
Symptoms: Person has a small head widely spaced eyes, moon like face , cry like kitten, and congenital heart disease.

21-monosomy

Caused by the complete loss of one chromosome of the 21^st chromosome pair.
45 chromosomes only
Symptoms: Nose is prominent and distance between the eyes is less than normal, ears are large and muscles are contracted.

Myelogenous leukemia

Caused by the deletion of some portion of long arm of chromosome 22 and its addition to chromosome 9 (Reciprocal translocation)

Philadelphia chromosome

It brings about change in the conformation of C-Abl protein and activates a latent oncogenic potential causing production of excess of granular leuckocytes and hence called chronic granulytic leukemia . This 22 nd chromosome whose a little segment from long arm is deleted , is called Philadelphia chromosome, as it was first reported in the city of Philadelphia in 1959.

Alzheimer's disease

Neuro-degenerative disease of brain is caused by the accumulation of Amyloid protein plaques in the brain resulting in the degeneration of neurons.
The protein involved, Amyloid β peptide is produced and processed in a number of ways in the brain.
This disease is due to ageing and involvement of two defective alleles, one on the chromosome -21 and other on chromosome 19.