Cool Stuff about Chromosomes

Y they’re X-cellent Sex chromosomes – determine whether the offspring is male or female Females: XX Males: XY

Boy or Girl?

Who determines the gender of the offspring?

King Henry VIII

Autosomes – all of the non-sex chromosomes How many chromosomes are autosomes? How many are sex chromosomes?

Studying Chromosomes Karyotype – a photograph of all an organism’s chromosomes

How are karyotypes made? Scientists use chemicals to freeze cells at the metaphase stage of cell division Easy to isolate and easy to stain

Arrange the chromosomes

Reading a chromosome Look at 3 things: Size Banding pattern Centromere position

http://learn.genetics.utah.edu/content/begin/traits/karyotype/

Genome Genome – the base sequence of all the DNA in an organism

What is The Human Genome Project? Find the sequence of all the DNA in the human body “read” 23 chromosomes which contain about 90,000 genes with more than 3 billion bases.

Cracking the Code of Life

Chromosomal Abnormalities Karyotypes can be used to show chromosome abnormalities Too many or too few chromosomes

Chromosomal Abnormalities Nondisjuction – chromosomes fail to separate correctly during mitosis or meiosis Mitosis

Nondisjuction Meiosis Abnormal gametes

Nondisunction Monosomy – zygote has only one copy of a particular chromosome

Nondisunction Trisomy – zygote has three copies of a chromosome

What’s wrong with the karyotype?

Trisomy 21 Down syndrome

Down Syndrome – most common chromosome abnormality in humans Lower cognitive ability, Flattened face with angled eyes, Shorter stature (5’1, 4’9), Usually infertal

What’s wrong with this karyotype?

XXX Triple-X Not severe symptoms - Slight learning disabilities, usually tall Fertile with rare chance of passing on disease

What’s wrong with this karyotype?

XXY Klinefelter syndrome Symptoms include learning disabilities, slight breast development, wider hips, underdeveloped male organs, and infertility.

What’s wrong with this karyotype?

X0 Turner syndrome Symptoms include short child like stature, underdeveloped female organs, low hairline, neck webbing, and infertility.