2. Cell Reproduction Notes Day 1 Warm Up Where are your genes located?

3. http://people.na.infn.it/~nicodem/research/cell_genes.jpg

4. DURING MOST OF THE CELL’S LIFE, DNA FORMS A TANGLED MASS CALLED CHROMATIN. CHROMATIN LOOKS LIKE A PLATE OF SPAGHETTI. RIGHT BEFORE A CELL DIVIDES, THE CHROMATIN FORMS INTO CHROMOSOMES (X- SHAPED).

5. MOST OF THE TIMEONCE IN A WHILE CHROMATIN CHROMOSOMES

7. Cell Division Chromosomes = Tightly coiled, rod-shaped DNA Chromosomes are made of chromatin Human body produces 2 trillion cells per day & 25 million per second Cells are formed by cell division of older cells 1.When a cell divides, DNA is first copied & then distributed 2.Each cell ends up with a complete set of DNA

8. Chromosome Number Each human somatic cell has 2 copies of 23 different chromosomes –Total 46 –Somatic = any cell that is NOT a sex cell –(also called body cells or autosomes)

9. Sets of Chromosomes Each pair is made up of 2 homologous chromosomes –Homologous chromosomes = chromosomes that are similar in size, shape, & genetic content –Each homologue comes from one of the parents One from mom One from dad

10. Cells Can Be Diploid or Haploid Diploid = a cell that contains 2 sets of chromosomes (2n) Haploid (monoploid) = a cell that contains only 1 set of chromosomes (1n or n)

11. Chromosomes Determine Your Gender Humans have 23 pairs of chromosomes 22 pairs are autosomes (chromosomes NOT directly involved in determining sex) 1 pair are sex chromosomes (contain genes that WILL determine the sex) –X & Y chromosomes

12. X & Y Chromosomes Male = XY Female = XX Male (dad) can donate an X or a Y to offspring Female (mom) can ONLY donate an X So-Which parent determines the sex of the baby?

13. MALE XY

14. Gametes Gametes are reproductive cells –Males = sperm (n = 23) –Female = egg (n = 23) Combine in fertilization to make a: –Zygote (n = 46)

15. Karyotype Karyotype = a photo of the chromosomes in a dividing cell that shows the chromosomes arranged by size.

16. Karyotype cont’d Each of an individual’s 46 chromosomes has thousands of genes so the presence of all chromosomes is essential for normal functioning –Humans who are missing a chromosome don’t survive –Humans with more than two copies of a chromosome, called trisomy, may survive but will not develop properly.

17. What is wrong?

20. The Cell Cycle Repeating sequence of cell growth and division during an organism’s life 90% of cell life is spent in INTERPHASE Then it may go into MITOSIS & CYTOKINESIS

21. INTERPHASE (divided into mini-phases) G1(first growth) phase = Cell grows rapidly S (synthesis) phase = DNA copied G2 (2 nd growth) phase = Nucleus prepares to divide

22. http://publications.nigms.nih.gov/insidethecell/ch4_interphase_big.html

23. AFTER INTERPHASE Mitosis Cytokinesis http://www.cellsalive.com/cell_cycle.htm

24. Mitosis and Meiosis WARM UP Females are X___ Males are X___ Having 3 copies of a chromosome is called a ______________

25. Mitosis and Meiosis Mitosis: -division of somatic (body) cells - results in two daughter cells that are identical Meiosis -division of gametes (sex cells)

26. Mitosis Interphase Prophase Metaphase Anaphase Telophase

27. The Cell Cycle is Carefully Controlled Key check points which feedback signals from the cell will delay the next step Controlled by proteins! 1.Cell Growth CHECKPOINT (G1) – Start – Nerve/muscle cells stop here 2. DNA Synthesis CHECKPOINT (G2) – Enzymes 3. Mitosis CHECKPOINT – Back to G1 phase

28. When Control is Lost -- Cancer Cancer = Cell growth is uncontrolled - does not respond to control mechanisms. Causes: Mutations that cause over-production of growth molecules – (accelerator) or by in- activating proteins that slow or stop the cell cycle (brakes) Tobacco and UV radiation linked to increased cancer risk.

29. Change in Chromosome Number Trisomy = humans with more than 2 copies of chromosomes – improper development Karyotype = a photo of the chromosomes in a dividing cell. Disjunction = when egg/sperm cells form – each chromosome and homologue separate – sometimes one or more chromosomes fail to separate - unequal distribution. Down Syndrome - 3 copies of chromosome 21- NONDISJUNCTION

31. Change in Chromosome Structure Mutation – A change in an organism’s chromosomal structure. Deletion = piece of chromosome breaks off completely – lacks of a set of genes – fatal Duplication = chromosome fragment attaches to its homologous chromosome –two copies of a gene set

33. Inversion = chromosome piece reattaches to original chromosome, but in reverse orientation. Translocation = chromosome piece reattaches to a nonhomologous chromosome.

36. Interphase Interesting things happen! 1.Cell preparing to divide 2.Genetic material doubles

37. Prophase Chromosome pair up! 1.Chromosomes thicken and shorten -become visible -2 chromatids joined by a centromere 2.Centrioles move to the opposite sides of the nucleus 3.Nucleolus disappears

39. Metaphase Chromosomes meet in the middle! 1.Chromosomes arrange at equator of cell 2.Become attached to spindle fibres by centromeres 3.Homologous chromosomes do not associate

41. Anaphase Chromosomes get pulled apart 1.Spindle fibres contract pulling chromatids to the opposite poles of the cell

42. Telophase Now there are almost two! 1.Chromosomes uncoil 2.Spindle fibres disintegrate 3.Centrioles replicate

44. Cytokinesis Cell splits

45. http://www.cellsalive.com/mitosis.h tm

46. Metaphase

47. Telophase

48. Prophase

49. Anaphase