2. Cell Growth and Reproduction (BIO.B.1)

4. DNA DEOXYRIBONUCLEIC ACID

5. DNA STRUCTURE The chemical components of DNA are: –sugar (deoxyribose) –phosphate groups –Four different nitrogen containing bases

6. THE FOUR BASES ARE: 1. Adenine 2. Guanine 3. Thymine 4. Cytosine

7. Nucleotide - made up of a sugar, a base, and a phosphate group. DNA is like a twisted ladder and is called a double helix.

9. The uprights of the ladder are made of the sugar and phosphate of the nucleotides. The rungs are two nitrogen bases held together by hydrogen bonds.

10. THE DNA LADDER Uprights = sugars and phosphates Each rung = 2 bases connected by H bonds

11. COMPLIMENTARY BASES Adenine binds with Thymine. Guanine binds with Cytosine.

12. Figure 16.5 The double helix

13. DNA Chromosome – a long strand of DNA –One chromosome (one strand of DNA) has thousands of genes and millions of base pairs –Humans have 46 chromosomes and have an estimated 23,000 - 25,000 genes Gene – a section of DNA that gives instructions for a protein to be made; the protein controls a trait

14. Genome – a sum of all of an organism’s genes Genetic code - the order of the bases –Different order = different genes –Different order = different people and even different species. Allele – the form that a gene takes (ex. some are dominant or recessive)

15. DNA Replicates DNA can make copies of itself (replicate). Why does DNA need to be able to copy itself? –DNA replicates so when cells divide to make new cells, the new cells have the same DNA as the original cell

16. REPLICATION OF DNA Replication begins with DNA Polymerase (an enzyme) binding to a part of DNA.

17. DNA polymerase breaks Hydrogen bonds between base pairs (unzips the DNA). The enzyme then adds complementary nucleotides to each new strand.

18. Each new DNA molecule consists of one original chain and one new chain. Proof-reader enzymes - proof- read the new chains and check for mistakes (these include DNA polymerase).

19. CELL DIVISION

20. Types of Cell Division Mitosis – makes new somatic (body) cells in eukaryotes Meiosis – makes new gametes (sex cells) in eukaryotes

21. WHY DIVIDE? Why do multicellular organisms do mitosis? –To repair or heal –To grow and develop –To replace cells that die Why do unicellular organisms do mitosis (eukaryotes)? –To reproduce asexually (cloning) Why do multicellular organisms for meiosis? –To reproduce sexually

22. Important part of Cell Division Nucleus - contains genetic information (DNA) Chromosomes – strands of DNA When a cell divides, the new cells made must have the correct number and kind of chromosomes. Most of the time, DNA looks like a lump of spaghetti, and is called chromatin.

23. Cell Cycle

24. Interphase –G 0 – cell at rest; is not preparing for division –G 1 – cell gets ready for division –S – chromosomes copy themselves –G 2 – cell checks for mistakes and prepares for division Mitosis – the process of nuclear division Cytokinesis – the division of the cells cytoplasm

25. Most of the time cells are not dividing. Several proteins are involved in starting division. Some cells can divide in as little as 20 minutes.

26. Cells typically stop dividing when: – Nutrient levels drop (no food) –They come into contact with other cells (no room) –Receive chemical signals to stop.

27. INTERPHASE Cells spend most of their life in interphase. Normal cell activities occur. To prepare for cell division, the chromosomes make copies of themselves. In other words, the DNA replicates. Recall, DNA polymerase… etc.

28. MITOSIS: NUCLEAR DIVISION FOR EUKARYOTES Four Stages 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase Cells Alive AnimationCells Alive Animation John Kyrk Animation McGraw AnimationJohn Kyrk AnimationMcGraw Animation

30. PROPHASE Chromatin condenses and becomes visible as chromosomes. The nucleus and its various parts disappear. Spindle fibers are made and attach to the chromosomes.

31. Centrioles separate and move to opposite ends (poles) of the cell. Each copy of the chromosome is called a chromatid.

32. Chromosome centromere chromatids

33. METAPHASE The chromosomes line up at the middle of the cell (equator).

34. ANAPHASE The joined chromatids separate and move to opposite ends of the cell.

35. TELOPHASE The chromatids arrive at the opposite poles of the cell. Spindle fibers disappear. New nuclei form in the two new cells. Cytokinesis - pinching in of plasma membrane (formation of cleavage) in order to form two new cells

36. END RESULTS OF MITOSIS Two new “daughter” cells are made with each containing the same number and kinds of chromosomes as the original (parent) cell. They have the same genetic code.

37. A Little Info on Cancer

38. CANCER Caused by uncontrollable mitosis. Cells either fail to stop dividing or get signals to continue dividing. An increased number of cells makes a tumor. Tumors can be benign (non-cancerous) or malignant (cancerous). Cancer cells spread (metastasis) throughout body, unlike normal cells!

39. Some Causes of Cancer Genetics Radiation Carcinogens (mutate DNA) Old Age Viruses –Can mutate DNA causing some cancers –Example: Human papillomavirus (HPV) associated with cervical cancer in women Poor diets

40. MEIOSIS: Making sex cells

41. CHROMOSOME NUMBER The number of chromosomes varies from one kind of organism to another. Humans have 46 chromosomes & fruit flies have 8. Some plants have hundreds.

44. Karyotype – a picture of chromosomes that shows the number and the size of chromosomes that a cell has Amniocentesis and Chorionic Villi Sampling– tests done on pregnant women in order to look at the chromosomes of the developing baby

45. Chromosomes of animal cells are usually paired. WHY? Humans have 23 pairs, fruit flies have 4 pairs. Haploid - the # of pairs or n Diploid - the total number of chromosomes or 2n For humans: n=23 and 2n=46

46. SEXUAL REPRODUCTION Fertilization - the combination of chromosomes (genetic information) from two sex cells (combining sperm and egg) Each sex cell gives half of the total chromosomes.

47. Sex cells are also called gametes. –Female sex cell = egg or ovum –Male sex cell = sperm Gametes are haploid (half the chromosomes).

48. Gamete Production Gametes are produced in gonads. Eggs are made in ovaries. –Females begin making their eggs before they are born! –They stop making eggs during menopause. Sperm are made in testes. –Males make sperm from approximately puberty until death.

49. After fertilization, the developing organism is called a zygote and is diploid. After fertilization the zygote grows bigger by doing MITOSIS. A zygote becomes an embryo and later a fetus.

52. MEIOSIS END RESULT Meiosis makes 4 haploid, sex cells. These 4 cells are sex cells (sperm and egg). Each cell has half the number of chromosomes as the parent cell (haploid). Meiosis increases genetic diversity in the offspring.