KaryotypesKaryotypes

Chromosomes are DNAChromosomes are DNA

Chromosome PartsChromosome Parts

centromere

chromatids

Each half is identical to the other. X shaped chromosomes form after DNA replication.

Normal KaryotypesNormal Karyotypes

What are the stripes on the chromosomes?

Homologous chromosomes

Sex chromosomes XX=girl XY=boy

DNA ReplicationDNA Replication

After DNA ReplicationAfter DNA Replication

When something goes wrong.When something goes wrong. Trisomy 13Trisomy 13

Down SyndromeDown Syndrome Nondisjunction of chromosome #21.Nondisjunction of chromosome #21. 47 chromosomes.47 chromosomes. Your chances of a down syndrome baby Your chances of a down syndrome baby

goes up as women get older.goes up as women get older.

Klinefelter syndromeKlinefelter syndrome

Extra X Extra X chromosome in a chromosome in a male.male.

XXYXXY Small male Small male

genitals, breast genitals, breast development, wide development, wide hips, and poor hips, and poor beard growth, beard growth, sterile.sterile.

Klinefelter syndromeKlinefelter syndrome

Extra Y Extra Y chromosome in a chromosome in a male.male.

XYYXYY Very tall man.Very tall man. Not much Not much

difference.difference.

Klinefelter syndromeKlinefelter syndrome

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

Turner syndromeTurner syndrome

Only one X.Only one X. Female.Female. XX Underdeveloped Underdeveloped

sex organs.sex organs. Short, and sterile.Short, and sterile.

cri du chat (cry of the cat)cri du chat (cry of the cat) Deletion in Deletion in

chromosome 5.chromosome 5. Babies cry like a Babies cry like a

cat’s meow.cat’s meow. Characteristic Characteristic

facial features.facial features.

2 Kinds of Mutations2 Kinds of Mutations Point mutationsPoint mutations = one base pair is = one base pair is

changed. (changes the protein)changed. (changes the protein) Chromosome mutationsChromosome mutations = large changes = large changes

in chromosomes. (changes many genes)in chromosomes. (changes many genes) Chromosome mutations can happen if Chromosome mutations can happen if

meiosis goes wrong.meiosis goes wrong.

Sometimes it is beneficial.Sometimes it is beneficial.

Humans have 99% the same DNA as Humans have 99% the same DNA as chimpanzees.chimpanzees.

Chimpanzees have an extra chromosome.Chimpanzees have an extra chromosome. The theory is that two chromosomes fused The theory is that two chromosomes fused

evolving the human race.evolving the human race. Play Video. – 5:05-7:30 – 5:05-7:30

Testing for chromosomal disordersTesting for chromosomal disorders AmniocentesisAmniocentesis UltrasoundUltrasound Karyotyping Karyotyping

The Doctor’s RoleThe Doctor’s Role

Perform tests to Perform tests to remove cells.remove cells.

Extract the DNA.Extract the DNA. Do a karyotype Do a karyotype

match the match the homologous homologous chromosomes chromosomes

Seek help from a Seek help from a Genetic Counselor. Genetic Counselor.

What’s wrong here?

The Human Genome ProjectThe Human Genome Project

If we can determine the baby’s karyotype If we can determine the baby’s karyotype then can we determine it’s genes?then can we determine it’s genes?

Yes, thanks to the human genome project Yes, thanks to the human genome project we can do a test for certain genes.we can do a test for certain genes.

In the future we could test for designer In the future we could test for designer traits.traits.