Chromosome Disorders Any syndrome malformations or malfunctions in

Chromosome Disorders

• Any syndrome (malformations or malfunctions in any of the body's systems) caused by abnormal chromosome number or structure.

I. Numerical Disorders • When the number of chromosomes in each cell is wrong (should be 46 in each cell 2 x 23) • Usually caused by a problem during cell division

• Examples: Write the name and chromosome problem. Example: Down Syndrome (Trisomy 21), Extra #21

1. Down Syndrome – Trisomy 21 • 1 in 900 births • Caused by an extra (third) chromosome 21.

2. Edwards Syndrome – Trisomy 18 • 1 in 3, 000

Also trisomy 18 or Edwards syndrome is a serious syndrome where the babies generally die in the first life year. The babies have malformations of many organs.

3. Turner Syndrome - Monosomy • 1 in 2500 female births • Caused by having only one X (no second X or Y)

Girls with Turner syndrome have 1 instead of 2 X chromosomes (monosomy X): they are small, have no menstruation and are sterile. Frequently also there exists a broad neck (webbed neck). The intellectual development is normal or slightly behind.

4. Klinefelter Syndrome - XXY Klinefelter syndrome (KS) occurs in some men who have more than one X chromosome (XXY).

II. Structural Mutations • Caused when a chromosome's structure is altered • Examples:

1. Wolf-Hirschhorn Syndrome • 1 in 50, 000 births • Partial deletion of the short arm of chromosome 4

2. Fragile X Syndrome • 1 in 4, 000 males, 1 in 8, 000 females • Partial duplication of the X chrom

Structural Mutations Deletion Duplication Inversion Translocation