1. Cell Reproduction
Chapter 3,
Section 5

2. Maintaining our bodies
Why do cells reproduce?
Growth
Healing
Maintaining our bodies

3. Chromosomes
Structures inside the nucleus that contains genetic information.
Chromosomes are made from long strands of DNA.

5. Parts of a Chromosome Chromatid- Identical strands of DNA.
Centromere- Connects the chromatids of each chromosome.

7. Numbers of Chromosomes
Organisms have different numbers of chromosomes.
Humans have 23 pairs of chromosomes, 46 in all.

8. Mitosis
The process in which the nucleus of a cell divides to form two identical nuclei.

9. Cell Cycles Cells do not live forever!
The cell cycle is a series of stages a cell goes through before it divides.

11. Pre Mitosis - Interphase
A period of growth and development.
Most of the cell’s life is spent in Interphase.
chromosomes are copied!

12. Steps of Mitosis
Prophase
Metaphase
Anaphase
Telophase

13. Step 1 - Prophase Nucleus disappears. Chromosomes thicken
Spindle fibers stretch across the cell.

14. Thread-like structures that pull the chromosomes apart.
Spindle Fibers
Thread-like structures that pull the chromosomes apart.

15. Spindle Fibers attach to the centromere.
Step 2 - Metaphase
Chromosomes line up along the center of the cell.
Spindle Fibers attach to the centromere.

16. to opposite sides of the cell.
Step 3 - Anaphase
The spindle fibers pull the chromosomes apart
to opposite sides of the cell.

17. Step 4 - Telophase Spindle fibers disappear. The nuclei reforms.
Chromosomes unwind.

18. Cytokinesis
The cell pinches along the middle and becomes two new cells!

23. Interphase I
Prophase
Metaphase
Cytokinesis
Anaphase
Telophase

24. Results of Mitosis One nucleus becomes two nuclei.
Our cells have 46 chromosomes (23 pairs).
After mitosis, a new nucleus with 46 chromosomes (23 pairs) is made.

25. DNA (Deoxyribonucleic Acid)
Chromosomes are made out of DNA.
DNA looks like a twisted ladder (called a double helix)
DNA codes for the creation of proteins.

26. Structure of DNA DNA is made up of a: Sugar Group Phosphate Group
Nitrogen Base

27. Guanine, Cytosine, Adenine, and Thymine,
Four Nitrogen Bases
Guanine, Cytosine, Adenine, and Thymine,
These bases make up the “steps” in the DNA ladder.

28. Chargaff’s Base Pairing Rules
Guanine always binds to Cytosine G----C
Adenine always binds to Thymine A----T

31. DNA Replication
In order for mitosis and meiosis to occur, DNA must replicate!
The DNA strand “unzips” and two new strands of DNA forms.

32. Hydrogen bond between the two bases breaks and the strands separate
Free floating nucleotides in the nucleus come and join with their complementary base pairs
This makes two strands of DNA that are identical to the original