Genetics: Karyotypes

Chromososmes Traits are passed on to you from your parents through chromosomes. Half of your chromosomes come from your father and half from your mother.

Karyotype – An ordered arrangement of a person’s chromosomes

Sex Chromosomes vs. Autosomes Sex Chromosomes (23rd pair)– The X and Y chromosomes which determine a person’s sex Which sex is XY? Male Which sex is XX? Female Autosomes – Paired chromosomes 1-22, same in both sexes

How Karyotypes are Made Cells of a person or fetus are photographed during mitosis when the chromosomes are condensed and easy to see - Prophase

How Karyotypes are Made The photograph is then cut and the chromosomes are arranged in order of size

Amniocentesis – taking the fluid from around a fetus to make a karyotype

Normal Human Karyotype 23 pairs of Chromsomes 1-22 - Autosomes 23 - sex chromosomes

Karyotype Abnormalities Monosomy- having one chromosome rather than a pair Trisomy – having three chromosomes rather than a pair Both occur because of nondisjunction during meiosis

Nondisjuction – when a doubled chromosome doesn’t split during meiosis These 4 cells will each become eggs or sperm, two of which will have abnormal numbers of chromosomes. Which two?

Trisomy 21 = Down’s Syndrome

Down Syndrome Happens 1 in 700 births Individuals have broad, flat faces, mild to moderate mental retardation, and sometimes respiratory problems Usually live slightly shortened life-spans

Trisomy 18 = Edward’s Syndrome

Edward’s Syndrome Happens 1 in 10,000 births Individuals have malformed ears and hands, mental retardation, and heart disease Most don’t live past a few years

47, XXY = Kleinfelter’s Syndrome

Kleinfelter’s Syndrome Happens 1 in 1000 male births Individuals are sterile, have some feminine characteristics such as breast enlargement and little facial hair, normal intelligence

Monosomy X = Turner’s Syndrome

Turner’s Syndrome Happens 1 in 5000 female births Individuals do not develop sexually during puberty and are sterile, but have normal intelligence The only monosomy that is survivable in humans!

What can you tell about this person from their karyotype?

Now, get out a piece of paper for the Karyotype Lab Do not write on the paper Following the instructions

1. Billy 2. Will 3. Tommy (left) 4. Suzy 5. Jen