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 Disorders
1. 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