Karyotypes

A photograph of a persons chromosomes (cut up and arranged in order)

How many chromosomes are present?Is this a somatic (body) cell or a

gamete?

Chromosomal Genetic Disorders1. Numerical:When an individual is missing either a chromosome from a pair (monosomy) or has more than two chromosomes of a pair (trisomy, tetrasomy, etc).

Examples:

Down Syndrome – (Trisomy 21) an individual has three copies of chromosome 21

Turner Syndrome – (monosomy) an individual is born with only one sex chromosome, an X.

Examples continued

• Klinefelter's syndrome – also known as XXY syndrome, a condition in which males have an extra X sex chromosome.

• Edwards Syndrome – (Trisomy 18) an individual has three copies of chromosome 18

Down Syndrome

• 1 in 900 births

Turner Syndrome

• 1 in 2500 female births

Klinefelter's syndrome• 1 in 1,000 births

Edwards Syndrome

• 1 in 3,000

2. Structural: When the chromosome's structure is altered.

a. Deletions: A part of a chromosome is missing or deleted.

b. Duplications: A portion of the chromosome is duplicated, resulting in extra genetic material.

Other structural disorders:

Translocations: When a portion of one chromosome is transferred to another chromosome.

Inversions: A portion of the chromosome has broken off, turned upside down and reattached, therefore the genetic material is inverted.

Rings: A portion of a chromosome has broken off and formed a circle or ring. This can happen with or without loss of genetic material.

Isochromosome: Formed by the mirror image copy of a chromosome segment including the centromere.

Wolf-Hirschhorn syndrome• 1 in 50,000 births