Cell Reproduction and Division

1. Cell Reproduction and Division How do cells get here?

2. Cell Cycle Figure 17.1

3. Interphase Cell cycle • The events that happen to a cell from when it is created to when it divides again. • Interphase: growth and cell living • G1: cell mass increases • S: DNA set is doubled • G2: components for division are made • some cells like neurons never leave interphase. M G1 G2 S

4. Human Life Cycle

5. A physical location exists for all genetic traits on a chromosome Chromosome map

6. Cell ReproductionResults Mitosis: all cells, 2 cells with same number of chromosomes Meiosis: only in gonads 4 cells are produced with a single set of 23 chromosomes What would cloning be?

7. Making an exact copy: cloning

8. When cells divide • When a cell divides each new cell receives DNA (instructions) and cytoplasmic machinery to start its own operation. • DNA: contains genes that code for proteins, which in turn serve as structural materials and enzymes. They give the body its appearance.

9. 46 46 46 23 23 23 23 46 Mitosis and Meiosis • Mitosis: used for growth of multicellular organisms • Meiosis: is used only in germ cells for the production of gametes.

10. Chromosomes • A complex of DNA and protein • Prior to division a copy is made and the two are held together at the centromere • The loose form in the nucleus is the chromatin

11. Chromosome Numbers • Chromosomes come in pairs, one from each parent • Chromosome pairs carry the same information and are called homologous chromosomes • n= haploid #, is the number of chromosome types • 2n=diploid number, all cells have 2 sets of chromosomes

12. Mitosis • Prophase: chromosomes condense • Metaphase: chromosomes line up • Anaphase: chromosomes begin to divide • Telophase: a new nucleus forms • Endpoint: 2 cells with half the cell mass but the same number of chromosomes, the cells are clones

13. Mitosis figure

14. Meiosis • Occurs in testes called spermatogenesis • Occurs in ovaries called oogenesis • Anaphase to telophase 1 results in haploid cells • Anaphase 2 to telophase 2 results in 4 haploid cells

17. Genetic variation is the result of • Crossing over that occurs during prophase I • Anaphase I- chromosomes separate randomly into haploid cells. • Of all the genetically diverse gametes produced, chance determines which will meet.

20. Information • During each division information must be moved from the mother cell to the daughter cells. • This info is held in the form of DNA • This info is due to the unique sequence of the DNA • One slight change in your DNA may be handed down to all the generations that follow.

21. The Why of Genetic variation

22. What gives variety to a sperm? What gives variety to an oocite? Why is it almost impossible for two people to be exactly alike? Why can people say “all whites look alike” “she looks just like her mother” “he looks like a Frenchman” Genetic Variation

23. DNA structure

25. Information flow in a cell. • Replication- DNApolymerase creates a copy of DNA from an old copy. Semiconservative replication • Transcription- RNApolymerase creates an RNA copy of a DNA gene template • Translation- Ribosomes convert the RNA gene template into a protein • The Central Dogma

27. Protein Synthesis: Transcription • Process: • DNA for a gene unwinds • RNA polymerase assists in copying base sequence in RNA nucleotides • Primary transcript made, includes introns and exons • Introns edited out • Messenger RNA strand produced

29. Genetic Code • Codon: sequence of three RNA bases, code for amino acids • Duplicate codons: all but one amino acid (methionine) have more than one codon • DNA grammar: • Start: AUG (methionine), begin all genes • Stop: UAA, UAG, UGA, one ends each gene

30. Three Steps of Translation Figure 17.8

33. Regulation of Cell Reproduction • Internal control mechanism • Regulate cell cycle: cyclins • Outside Influences • Can modify cell cycle: platelet-derived growth factor

34. Environmental Factors Influencing Cell Differentiation • Differentiation in early development: • After 8-cell stage, cells exposed to different environments inside versus outside the ball • To date embryonic cloning: can occur at 8-cell stage • Differentiation in later development: • Two factors: • Developmental history of earlier cells • Local environment

35. Even clones may not be exactly alike • Examples?