Chromosome Abnormalities

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Chromosome Abnormalities

Trisomy Conditions

Humans have 23 pairs of chromosomes

A trisomy is a chromosomal disorder characterised by an additional chromosome, so the person has 47 instead of 46 which leads to other physical/mental characteristics

Down Syndrome, Edward Syndrome and Patau Syndrome are the most common forms of trisomy.

... Down Syndrome

Extra copy of genetic material on the 21st chromosome (aka Trisomy 21)

An error in cell division "nondisjunction" resulting in the father's sperm or the mother's egg cell containing an extra/abnormal number of chromosomes

- Not usually genetic

Monosomy Conditions

Monosomy is when a diploid organism has only one copy of one of its chromosomes instead of two.

Very rare in autosomes - body cells without pairs don't tend to survive - but can occur in the sex chromosome

- E.g. Turner Syndrome

... Turner Syndrome

Tend to be short and struggles in reproduction

Characterised by one X and no second Chromosome (X or Y) on the sex chromosome

Not usually genetic