Chromosomes

Defined: Tightly coiled DNA
Forms during cell division
New chromosomes must be made for the new cell
2 Parts:
1) Chromatids: two identical parts of a chromosome
2) Centromere: Joins chromatids together
Defined: Picture of an individuals chromosomes
Used to determine sex and chromosome defects
Size of final pair indicates sex
Same size: XX = female
Different size: XY = male
Normal human will have 46 chromosomes
Which karyotype is a male?
Half of our chromosomes come from each parent (23 from each parent)
Diploid Cells = Cells with the full set of chromosomes
Somatic (non-sex) cells are diploid
Created by mitosis
Ex: Skin, Muscle, Nerve, Blood Cells
How many chromosomes do human brain cells have?
Haploid Cells = Cells with ½ the total number of chromosomes
Gametes (sex cells) are the only haploid cells
Chromosome number is reduced by meiosis
Ex: Sperm, Egg, Pollen
How do humans get 46 chromosomes?
Haploid sperm cells (23) + Haploid egg cell (23) = Diploid zygote (46)
Down Syndrome: What’s Wrong?
Writing notation:
1st: total chromosome #
2nd: Sex chromosomes
3rd: extra or missing
Down Syndrome: 47, XY, +21
Turner’s Syndrome: What’s Wrong?
Write the notation for Turner’s Syndrome.

45, X, -23

or

45, XO, -23
Patau’s Syndrome: What’s Wrong?
Write the notation for Patau’s Syndrome.

47, XY, +13
Klinefelter’s Syndrome: What’s Wrong?
Write the notation for Klinefelter’s Syndrome.

47, XXY, +23
What is the:
diploid number?
haploid number?

How many chromosomes would be in:
somatic cells?
blood cells?
How many chromosomes would be in:
gametes?
rat egg cells?
muscle cells?
Is this a male or female rat?
Quick Review
Chromsomes are tightly coiled strands of DNA
Diploid (somatic) cells contain the entire set of chromosomes
Haploid (gametes) cells contain only ½ the total number of chromosomes