Chromosomal Disorders

Deletion :

Wolf–Hirschhorn syndrome: It is a characteristic phenotype resulting from a partial deletion of chromosomal material of the short arm of chromosome 4. growth and mental retardation, muscle hypotonia, seizures, and congenital heart defects are the symptoms.

Karyotype : deletion of short arm of 4^th chromosome (4p)

Jacobsen syndrome: it is a rare congenital disorder resulting from deletion of a terminal region of chromosome 11 that includes band 11q24.1. It can cause intellectual disabilities, a distinctive facial appearance, and a variety of physical problems including heart defects and a bleeding disorder.

Karyotype : deletion of terminal region of 11^th chromosome ( 11q)

Turner’s Syndrome :

45,X, encompasses several conditions in human females, of which monosomy X (absence of an entire sex chromosome, the Barr body) is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent or has other abnormalities (unaffected humans have 46 chromosomes, of which two are sex chromosomes). In some cases, the chromosome is missing in some cells but not others, a condition referred to as mosaicism or "Turner mosaicism". In the majority of cases where monosomy occurs, the X chromosome comes from the mother.[10] This may be due to a nondisjunction in the father. Turner syndrome may be diagnosed by amniocentesis or chorionic villus sampling during pregnancy.

Karyotype : 45, XO

Down syndrome

Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is typically associated with physical growth delays, characteristic facial features and mild to moderate intellectual disability. The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age of an 8 or 9 year old child, but this varies widely. Down syndrome can be identified during pregnancy by prenatal screening followed by diagnostic testing, or after birth by direct observation and genetic testing.

Karyotype : 47, XY + 21 for male

47,XX +21 for female

Date: 2014-12-21; view: 1077