Chromosomes (Pre-IB SC 9)
What is chromatin?
Substance that contains DNA and proteins.
What is a chromosome?
A long DNA molecule with the genetic material of an organism.
When do chromosomes take on their distinct shape?
When eukaryotic cells are ready to divide, chromatin coils up into a very compact X-shaped chromosome.
What are the centers of chromosomes called? How does this help us count chromosomes?
- Centromeres
- Their position helps scientists tell chromosomes apart. Chromosomes are counted by their centromeres.
How many chromosomes do MOST cells of the human body have? What is the exception?
- 46
- Sperm and egg cells have 23
Which pair of chromosomes determines the sex? How is the sex determined?
- 23rd pair
- In males, 23rd pair = XY
- In females, 23rd pair = XX
What are genes?
Small segments of DNA located at specific places on a chromosome.