1. Chapter 8 Cell Reproduction

2. 8-1 Chromosomes

3. DNA Long, thin molecule that stores genetic information Instructions for Life

4. Chromosomes DNA coiled up This happens during cell division

5. Histones Proteins that the DNA wraps around to make chromosomes

6. Chromatid Each half of a chromosome “sister chromatids” = chromosome

7. Centromere Holds chromatids together until they separate during cell division

8. Chromatin Less tightly coiled DNA/protein Happens when the cell is NOT dividing so the information can be used

9. Chromosome Numbers Each species has its own number of chromosomes in each cell Ex: Fruit Flies = 8 Carrot = 18 Cat = 32 Human = 46

10. Two Types of Chromosomes 1. Sex chromosomes 2. autosomes

11. Sex Chromosomes Chromosomes that determine if an animal is a male or a female Females = X and X Males = X and Y

12. Autosome All other chromosomes that do not determine the sex of an animal Each cell has two copies of each autosome Example: DNA for eye color

13. Homologous Chromosomes The two copies of each autosome Same size and shape Carry genes for the same traits (for example blue eye color)

14. Karyotype A picture of homologous chromosomes

16. Diploid Cells with two sets of chromosomes

17. Haploid One set of chromosomes Ex: human sperm and egg cells

18. Chapter 8.3 Meiosis

19. Types of Reproduction Asexual reproduction –Produce offspring with only ONE parent –“babies” are identical to parent Sexual reproduction –Produce offspring by meiosis and the joining of the sperm and egg –“babies” are NOT identical to parents

21. Meiosis –New cells have half the number of chromosomes Gametes –Reproductive cells (sperm and egg)

22. Key Points Meiosis must happen so when the sperm and egg join to create a new organism, it has the correct number of chromosomes. Examples: –Human = 46 –Egg = 23 –Sperm = 23 –Egg + Sperm = baby –23 + 23 = 46

23. Meiosis I. (very similar to mitosis) Prophase I. –DNA coils into chromosomes –Each chromosome lines up with its homologue (the similar chromosomes) –Synapsis: pairing of homologous chromosomes –Each pair is called a tetrad –Crossing-over: may occur where pieces of one chromosome break off and attach to the other chromosome  genetic recombination

25. Metaphase I. –Tetrads line up along the middle of the cell

27. Anaphase I. –Each homologous chromosome of each tetrad moves to opposite ends of the cell

29. Telophase I. –Cell divides creating 2 new cells each with a haploid number of chromosomes (1/2 the original number of chromosomes, but 2 copies of each)

31. Meiosis II. (DNA does NOT get copied first) Prophase II. –Chromosomes begin to move

33. Metaphase II. –Chromosomes move to the cell’s midline

35. Anaphase II. –Chromatids separate and move to opposite ends of the cell

37. Telophase II. –Four new cells form with ½ the original number of chromosomes

39. **Meiosis occurs ONLY IN REPRODUCTIVE ORGANS. See Figure 8-12 page 155

40. Spermatogenesis: –Production of sperm cells Oogenesis: –Production of egg cells