A karyotype refers to all the chromosomes in a genome, meaning 23 pairs of chromosomes or 46 in total. When the chromosomes are displayed in order of size like you see on the screen, we call that a karyogram. Each pair of chromosomes has been inherited from our parents, meaning one chromosome from the mother and the other from the father.

Pairs 1-22 are referred to as autosomal chromosomes, meaning that they contain genes that are not responsible for determining the sex of the person. While each pair of the autosomal chromosomes came from different people, one from mom and the other from dad, they still have the same contents, meaning the same kind of genes in the same locations.

The 23rd pair are referred to as the sex chromosomes, since this pair determines the sex of the individual. Boys inherit the Y chromosome from their father and the X chromosome from their mother while girls inherit 2 X chromosomes, one from their mother and one from their father.

When reading a karyogram to check for genetic diseases you want to check the number and shape of the chromosomes. An incorrect number of chromosomes is known as *aneuploidy.* Observing 1 chromosome instead of 2, it is referred to as monosomy. Observing 3 chromosomes instead of 2, it is referred to as trisomy. When checking the shape of the chromosome you want to make sure that it is not too long nor too short, either of which could cause a disease.

Let’s walk through 5 of the more common genetic diseases which can be detected through karyotyping:

1. Down syndrome which is caused by a third chromosome on pair 21.
2. Edward’s syndrome which is caused by a third chromosome on pair 18.
3. Patau syndrome which is caused by a third chromosome on pair 13.
1. Both Edward’s and Patau syndrome are usually fatal.
4. Klinefelter syndrome is caused by an additional X chromosome in boys and may cause slowed puberty and infertility.
5. Turner syndrome is caused by a missing or damaged X chromosome in girls, causing heart and neck problems as well as a decrease in height.

Sources:

Nicole's channel:    • Reading Karyotypes  

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