Cell Growth and Division Cell Cycle:

1. Cell Growth and Division • Cell Cycle: • Sequence of events that occurs in a cell from mitosis to mitosis. • 5 parts: • G1 phase – cell growth occurs (make new proteins + organelles). • S phase – DNA is copied in preparation for mitosis. • G2 phase – Organelles needed for nuclear division are made. • Mitosis – nuclear division. • Cytokinesis – cytoplasm divides. • Interphase – G1 + S + G2 phases.

2. Figure 10-4 page 245

3. Mitosis • Chromosome structure:

4. Done to produce more cells (growth and replacement). • Occurs in somatic cells (body cells) not sex cells (gametes) • 4 steps: • Prophase: • Nuclear membrane + nucleolus disappear. • Chromosomes condense + become visible. • Centrioles form + move to poles. • Spindle fibers first appear.

5. Metaphase: • Spindle fibers attach to centromere (center of chromosome). • Chromosomes line up at the equator. • Anaphase: • Sister chromatids spilt. • Chromosomes (now w/ only 1 chromatid) move to opposite poles. • Telophase: • Nuclear membrane + nucleolus reappear. • Chromosomes spread out + become invisible. • Spindle fibers disappear.

6. Figure 10-5 page 246-47

7. Cytokinesis – division of the cytoplasm. • After mitosis, one cell with two nuclei. • Animals – cytoplasm pinches in (cleavage furrow) • Plants – cell plate forms in the center and works towards the cell wall. • Figure 10-6 page 248

8. Uncontrolled cell growth • Cancer – uncontrolled cell growth (tumor). • Causes: • Smoking/chewing tobacco • Radiation exposure (X-rays, tanning beds, etc.) • Viruses • Other (chemicals, defective genes, etc.)

9. Production of Sex Cells • Meiosis • Nuclear division that reduces the number of chromosomes by half. • Production of gametes (sex cells: sperm + eggs) • Homologous chromosomes – pairs of the same chromosomes • Humans – 46 chromosomes (23 pairs) • Diploid – both homologs are present (2N) • Haploid – only 1 chromosome of each homolog pair is present. (1N)

10. 2 parts: • Meiosis I • Meiosis II • Meiosis I • Prophase I: 2N • Chromosomes become visible. • Nuclear membrane + nucleolus disappear. • Spindle fibers appear. • Synapsis (pairing of homologs) occurs. • Forms a tetrad (4 chromatids = 2 chromosomes). • DNA may be exchanged between tetrad (crossing over) = genetic variety

11. Metaphase I: 2N • Tetrads move to equator by the spindle fibers. • Anaphase I: 2N -> 1N • Tetrad splits, however each chromosome still has two chromatids. • Telophase I: 1N • Cytoplasm divides. • Nuclear membrane + nucleolus reappear. • Spindle fibers disappear. • Now have two cells.

12. Meiosis II (1N) • Prophase II: • New spindle fibers form. • Nuclear membrane + nucleolus disappear. • Metaphase II: • Chromosomes move to equator by spindle fibers. • Anaphase II: • Sister chromatids are split with each chromatid moving to opposite poles. • Telophase II: • Same as Telophase I. • Have 4 cells now.

13. Figure 11-15 page 276 – 77 Meiosis I

14. Meiosis II

15. Summary:15 StartEnd Mitosis: 1 cell, 2N 2 cells, 2N Meiosis: 1 cell, 2N 4 cells, 1N • Human gamete Production • Males = 4 (1N) sperm cells from Meiosis. • Starts at puberty • Females = 1 egg (1N) + 3 polar bodies (garbage). • Starts in the womb but not completed until ovulation.

16. Figure 11-7, page 278

17. Deoxyribonucleic acid, DNA – double helix molecule that carries hereditary information for genes. • Structure: • Composed of 3 parts: • Deoxyribose (sugar) • Phosphate group • Nitrogen base • Double helix shape • Discovered by James Watson and Francis Crick. • Twisted ladder shape.

18. Figure 12-7 page 294 • Four Nitrogen Bases • Adenine (A) Purine • Guanine (G) “ • Thymine (T) Pyrimidine • Cytosine (C) “

19. Bonding patterns: • G ≡ C (3 bonds) • A = T (2 bonds) • Replication – process of copying a DNA molecule. • Needed for mitosis (S phase) • Ribonucleic acid, RNA – single strand nucleic acid used for protein synthesis. • Different from DNA: • Single stranded • Ribose not Deoxyribose • Uracil instead of Thymine (A = U)

20. Types: • Messenger RNA (mRNA) – carries message from DNA to make proteins. • Transfer RNA (tRNA) – brings amino acids to ribosome to make proteins. • Ribosomal RNA (rRNA) – makes up the ribosomes. • Figure 12-12 page 300

21. Transcription – process of making RNA from DNA. • DNA  all types of RNA • Ex:

22. Protein synthesis – formation of proteins using genetic code from DNA and carried out by RNA. • Translation – process of forming proteins from mRNA. • mRNA leaves nucleus (nuclear pores) and goes to ribosomes. • mRNA is grouped into 3 consecutive bases called codons. • Each codon corresponds with a certain amino acid.

23. Figure 12-17 page 303

24. DNA – transcription – mRNA – translation – proteins • tRNA has a compliment (opposite) base sequence to the codon called anticodon. • The amino acid that corresponds with the codon is attached to the tRNA.

25. Figure 12-18 page 304

26. Mutations – spontaneous changes in a gene or chromosome. • Many types • Single Base switch: • Ex: NormalMutation DNA: ATG CGA GTG CGA RNA: UAC GCU CAC GCU AA : Tyrosine Histidine - Arginine - Arginine

27. Single Base Deletion: • Ex: NormalMutation DNA: ATG CGA T AGC GAT RNA: UAC GCU A UCG CUA AA : Tyrosine Serine - Leucine - Arginine • Environmental factors may cause, but not always. • Not passed to offspring unless occurs in gametes (sex cells)