1. Ch. 8: Cell Reproduction

2. DNA Stores genetic information Found coiled as Chromosomes during cell division Found a thin threads called Chromatin between cell divisions

3. Chromosome structure & number differ between Eukaryotes & Prokaryotes Prokaryotes: usually ONE circular chromosome

4. Chromosomes in Eukaryotes Rod-shaped DNA condenses by: wrapping around proteins called histones folding, twisting, & coiling http://www.youtube.com/watch?v=9kQpYdCnU14

6. Chromosome Structure Each chromosome has 2 identical halves called Chromatids Centromere – point of attachment between two chromatids

8. Chromosome Number Each species has characteristic # of chromosomes ex:HUMANS = 46

9. 2 types of chromosomes 1. Sex Chromosomes Determine gender May also carry other traits Humans have 2 forms: X or Y Males = XY Females = XX Which parent determines gender?

10. 2. Autosomes Other 44 chromosomes / 22 pairs Determine traits other than sex each copy in a pair is Homologous: same size, shape and carry genes for the SAME TRAITS

11. HUMANS 2 sex chromosomes (1 pair) ‏ + 44 autosomes (22 pairs) ‏ = 46 chromosomes Karyotype – diagram that shows chromosomes arranged in homologous pairs

12. Normal Male 46 XY

13. Normal Female 46 XX

14. Diploid & Haploid Cells 1. Diploid Cells (2n) ‏ have 2 sets of chromosomes 46 chromosomes: 2 sex chromosomes + 44 autosomes ALL human cells EXCEPT gametes (sex cells) are diploid

15. 2. Haploid Cells (1n) ‏ have only 1 set of chromosomes 23 chromosomes: 1 sex chromosome, 22 autosomes In humans, only gametes are haploid Gametes are reproductive cells Males = sperm females = ova

16. Fertilization restores diploid # in cells: Sperm + Ovum = Zygote (fertilized egg) ‏ 1n + 1n = 2n 23 + 23 = 46

17. Why do cells divide? There are limits to cell growth Surface-to-volume ratio Lg. cells have harder time diffusing materials in/out of cell DNA can only produce a limited amount RNA Cell will divide when it can’t grow any more

18. Uncontrolled Cell Growth Cancer: cells have lost ability to control growth. do not stop growing when they touch other cells continue to grow until the supply of nutrients is gone (death).

19. Cell Division Process where cells divide producing offspring cells 2 types: Mitosis Produces 2 offspring cells Offspring are genetically identical to original cell Meiosis Produces 4 gametes Offspring are genetically different from original cell

20. The Cell Cycle Time from the beginning of one division to the beginning of the next. During one cell cycle: the cell grows prepares for division divides to form offspring cells

21. Stages of the cell cycle Interphase- time in between divisions Mitosis / Meiosis- chromosome division and separation Cytokinesis- division of the cytoplasm: forms 2 cells

22. Interphase Longest stage of cell cycle 3 steps: G1: cell grows S: DNA replication occurs G2: cell prepares for division

23. Mitosis Division of the nucleus occurs for growth or to replace old cells Mitosis has four stages: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase “Please Make Anna Toast”

24. Prophase Longest stage Chromosomes condense & become visible Centrioles move to opposite sides of cell Nuclear envelope breaks down Spindle fibers form

26. Metaphase Shortest phase Chromosomes line up along equator (center) of cell

27. Sister chromatids separate & become individual chromosomes Chromosomes move toward opposite poles Anaphase

29. Telophase Chromosomes uncoil Nuclear envelope reforms around chromatin Spindle breaks down

31. Cytokinesis Begins as soon as nuclei reform Cytoplasm divides: -animal cells: membrane pinches in (cleavage furrow) -plant cells: cell plate forms http://www.youtube.com/watch?v=cvlpmmv B_m4

32. Meiosis Division to form reproductive cells aka: gametogenesis Produces 4 haploid gametes (sex cells) ‏

33. Meiosis = 2 rounds of division Meiosis I: DNA replicates & cell divides producing 2 haploid cells Meiosis II: 2 cells divide (w/o DNA replication) forming 4 haploid cells

35. Meiosis I Prophase I: synapsis occurs: chromosomes line up in homologous pairs called tetrads crossing over occurs: chromosomes in tetrads exchange genetic material -creates new combinations of genes

36. Metaphase I: Tetrads line up along equator Anaphase I: Independent assortment occurs: homologous chromosomes randomly separate to opposite poles creates genetic variation

37. Telophase I: Chromosomes uncoil Nuclear envelope reforms Cytokinesis I: 2 haploid cells produced Haploid b/c each has 23 chromosomes w/ 2 chromatids Genetically different

38. Meiosis II No Interphase between meiosis I & II – This means DNA does NOT replicate! Prophase II – Chromosomes coil, etc. Metaphase II – Chromosomes line up on equator

39. Anaphase II – Sister chromatids separate Telophase II – Chromosomes uncoil, etc Cytokinesis II – 2 cells split producing 4 gamete http://www.youtube.com/watch?v=D1_- mQS_FZ0

40. Gender Differences o Meiosis in males (spermatogenesis) produces 4 sperm o Meiosis in females (Oogenesis) produces 1 ovum & 3 polar bodies - b/c cytokinesis is uneven - polar bodies should dissolve