1. Biology 30 Cell Division

2. Where is DNA found? Put these terms in order from biggest to smallest
Gene -DNA
Organism -Cell
Chromosome -Nucleus

3. Where is DNA found?

4. Terminology Chromosome = compressed string of DNA
Sister chromatids
Chromosome = compressed string of DNA
Chromatin = DNA that is unwound (not compressed into a chromosome); found when cell is not dividing
Sister chromatids = a chromosome duplicates to make 2 identical copies (DNA replication)
Telomere
Centromere
- where chromatids join together

5. Chromosomes, genes and DNA
<>
Chromosomes, genes and DNA
Genes are DNA sequences located on chromosomes
Strand 1: A T G C C G A A
Strand 2: T A C G G C T T

6. Chromosomes, Genes and DNA
Chromosomes are just tightly wound chromatin
Only visible during mitosis
Otherwise, exist as a stringy mass called chromatin
Chromatin = DNA + Histones (protein)

7. DNA + Histones
= Chromatin

8. Human DNA
Fun Facts:
- Human DNA is 3 billion base pairs and about 2 m in length.
50% of the genes found in humans are also found in bananas
We have 65% genetic similarity to fruit flies

9. Why do cells divide?
Cells grow because proteins and organelles accumulate in the cytoplasm
Cells divide because the surface area of the cell membrane becomes inadequate (volume vs. surface ratio)
Cells die and need to be replaced
In order to reproduce the cell must pass on it’s genetic information

10. What happens next?
Our cells must be able to divide.
There are 2 types of cell division:
Asexual cell division – occurs in somatic (body) cell division = Mitosis
2. Sexual cell division – occurs in sex cells (germ cells) = Meiosis

11. Asexual Reproduction
The cells in our bodies started from a single cell called a ________ (think back to reproduction)
We constantly replace old/dying cells and are able to heal wounds, thanks to cell division

12. The Cell Cycle
The Cell Cycle has 4 major stages broken into 2 parts (Interphase and Mitosis)
Interphase:
- Cell spends 90% of time in Interphase
prepares cell for division; cell grows and makes organelles
DNA is in the form of chromatin
DNA replication occurs

13. Cell Cycle - Interphase
Interphase has 3 parts
G1 (Gap 1) –rapid growth phase where cells grow and new organelles are made, protein synthesis occurs
S (Synthesis) – genetic material in the cell doubles (DNA replication); therefore each daughter cell receives a full set of genetic material
G2 (Gap 2) – growth and preparation for division

14. The Cell Cycle: Summary
G1, S and G2 make up interphase
This is the process of cell activity between cell division
Cells grow and prepare for division in this stage
~ 90% of the cell cycle is interphase
Mitosis (M) is the process by which the cell divides
~ 10% of the cell cycle is mitosis