1. Cell division

2. Chromosomes Made of DNA Carries cell genetic information 23 pair
Differs for different organisms
fruit fly: 8
Carrot: 18

3. chromosomes Before a cell can divide it must duplicate DNA
Each chromosome consists of identical sister chromatids
Since they are identical, where will each one go?
One goes to each new cell
Each pair of chromatids are attached at centromere
Usually located near the middle of chromosome

5. Cell cycle Series of events that cells undergo as they grow and divide
During cell cycle the cell:
Grows
Prepares for division
Divides to form 2 daughter cells, each of which will re-enter into cell cycle

6. Cell cycle Interphase: “in-between” period of growth
Time spent Between divisions
Cycle consists of 3 phases: G1 S G2

7. Cell cycle: G1 (growth)
Most of the growing
Synthesize proteins

8. Cell cycle: S phase Chromosomes get replicated Synthesis of DNA
When completed, cell completes remainder of cycle

9. Cell cycle: G2 Shortest of phases Cells prepare for division
Organelles reproduced
Molecules needed for replication created

10. Mitosis Mitosis: process in cell division where nucleus divides
Divided into 4 stages
Prophase
Metaphase
Anaphase
Telophase

11. prophase First and longest phase Chromosomes become visible
Centrioles separate and move to poles
Centrioles help organize mitotic spindle (spindle apparatus): fanlike microtubule structure that helps separate chromosomes
Nuclear envelope breaks down
Chromosomes attached to fibers in spindle at the centromere

12. metaphase
Chromosomes line up in middle of cell

13. anaphase
Each sister chromatid separates and becomes an individual chromosome
Centromeres split
Chromosomes continue to move until they are in opposite poles

14. telophase Chromosomes uncondense Spindle breaks apart
Nuclear envelope reforms
Essentially, the opposite of prophase

15. cytokinesis Separation of cytoplasm and its contents
In animal cells, membrane is squeezed in the middle until 2 cells are formed
Cleavage furrow
In plant cells, a cell plate will form
This will eventually become the cell wall

17. Uncontrolled cell growth
Cancer
Cancerous cells do not respond to signals that regulate growth of most cells
Divide uncontrollably  tumor
Cells can break lose and travel to other parts of body
Metastizing
Causes can be genetic or environmental
Effects depend on affected tissue

18. Chromosome number review
Humans have how many chromosomes?
23 pairs of homologous chromosomes
We get half from mom and the other half from dad
=46
Diploid cell: contains 2 sets of chromosomes
Represented as 2n (n=number of chromosomes of organism)
Diploid cells contain 2 complete sets of genes

19. Chromosome number Haploid cells: contain only a single set of genes
Represented as n (n= number of chromosomes)
Diploid number for humans? 2n=?...
2n=46
Haploid number in humans? N
If 2n=46, then n=
n=23

20. Haploid cells
Haploid cells are found in sexually reproducing organisms
Each parent offers on set of their own DNA (n)
Combination of gametes (sex cells) n + n = 2n
In humans:
Sperm (n) has 23 chromosomes
Egg (n) has 23 chromosomes
They combine to form a diploid zygote (2n)

21. Section 10-3 Meiosis
Meiosis: process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
***Very similar to mitosis only with an extra set of phases

22. Meiosis Composed of two distinct divisions
Meiosis I
Meiosis II
Begins with a single diploid cell
Ends with 4 haploid cells

23. Homologous chromosomes
Homologous chromosomes: pairs of corresponding chromosomes from each parent
Ex. # 12 from mom matched up with # 12 from dad

24. Meiosis 1: Prior: chromosomes replicated
Meiosis I: division of Homologous chromosomes
Results in 2 haploid daughter cells
Prophase I, Metaphase I, Anaphase I, Telophase I and cytokinesis

25. Prophase I:
Homologous chromosomes pair up (one from each parent) to form a tetrad (structure formed when homologues come together)
Crossing over occurs: results in the exchange of genetic information between homologous chromosomes
Produces new combinations of genes

26. Crossing over Occurs during Prophase I
Overlapping arms of homologues have same information and can swap info at any point along their length
*****increases genetic variation*****

27. Metaphase I Spindle fibers attach to centromere
Tetrads (pair of homologous chromosomes) line up in middle of cell independent of each other

28. Anaphase I
Spindle Fibers pull homologous chromosomes toward opposite ends of the cell

29. Telophase I and Cytokinesis
Nuclear membranes reform
Cell separates to become two cells
*Cells produced have different genetic composition than the parent cell

30. Meiosis II Meiosis II: paired chromatids divide
Each cell now has 2 chromatids
Almost exactly like mitosis!!

31. Prophase II Nothing really happens
Chromosomes are already condensed and compacted
Nuclear envelope goes away

32. Metaphase II
Chromosomes line up similar to mitosis

33. Anaphase II
Paired chromatids separated

34. Telophase II and cytokinesis
Four haploid cells have been created

35. overview 2n n
Meiosis I
Meiosis II

36. Gamete formation Gamete: cell designed for sexual reproduction
Example: sperm and egg
Males make four sperm while females make one