Karyotypes

Chromosomes are DNA

Chromosome Parts Each half is identical to the other. X shaped chromosomes form after DNA replication. centromere chromatids

Normal Karyotypes What are the stripes on the chromosomes? Homologous chromosomes What are the stripes on the chromosomes? Sex chromosomes XX=girl XY=boy

DNA Replication

After DNA Replication

When something goes wrong. Trisomy 13

Down Syndrome Nondisjunction of chromosome #21. 47 chromosomes. Your chances of a down syndrome baby goes up as women get older.

Klinefelter syndrome Extra X chromosome in a male. XXY Small male genitals, breast development, wide hips, and poor beard growth, sterile.

Klinefelter syndrome Extra Y chromosome in a male. XYY Very tall man. Not much difference.

Klinefelter syndrome Extra X chromosome in a female. XXX Can’t tell at all. No difference from XX.

Turner syndrome Only one X. Female. X Underdeveloped sex organs. Short, and sterile.

cri du chat (cry of the cat) Deletion in chromosome 5. Babies cry like a cat’s meow. Characteristic facial features.

2 Kinds of Mutations Point mutations = one base pair is changed. (changes the protein) Chromosome mutations = large changes in chromosomes. (changes many genes) Chromosome mutations can happen if meiosis goes wrong.

Sometimes it is beneficial. Humans have 99% the same DNA as chimpanzees. Chimpanzees have an extra chromosome. The theory is that two chromosomes fused evolving the human race. Play Video. – 5:05-7:30

Testing for chromosomal disorders Amniocentesis Ultrasound Karyotyping

The Doctor’s Role Perform tests to remove cells. What’s wrong here? Extract the DNA. Do a karyotype match the homologous chromosomes Seek help from a Genetic Counselor. What’s wrong here?

The Human Genome Project If we can determine the baby’s karyotype then can we determine it’s genes? Yes, thanks to the human genome project we can do a test for certain genes. In the future we could test for designer traits.