What is mitosis? -Process in which a cell divides, creating TWO complete Sets of the original cell with the same EXACT genetic Material (DNA)

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1 What is mitosis? -Process in which a cell divides, creating TWO complete Sets of the original cell with the same EXACT genetic Material (DNA) Cell Division Produces CLONES with the same # of chromosomes and same EXACT chromosomes

2 -DNA Replicates (Copies itself) -copied DNA Pairs up -Nuclear membrane Disappears -Paired chromosomes Meet in the middle -chromosomes Are pulled apart -Mitosis is rapid cell division and produces large # s of offspring Ex: Skin Cell (Body Cell) Is mitosis Asexual or Sexual Reproduction? -Two complete Cells formed Identical to original -cytoplasm pinches in -nuclear membrane reappears -Asexual

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5 What is cancer? -Uncontrollable cell division Cancer is rapid MITOTIC cell division

6 How can I remember the stages of mitosis? P= pair up M= meet A= apart T= two

7 Chromosome- Coiled strands of genetic material (DNA) found inside the nucleus of eukaryotic cells Haploid- Cell that contains ½ the normal number of chromosomes (n) Diploid- Ex: Human Cell=23, Potato Cell= 24 Cell that contains the full number of chromosomes (2n) Ex: Human cell = 46, potato cell= 48 Chromatin- Long strands of DNA found in the nucleus

8 Homologous Chromosomes- A pair of chromosomes that are the same length and have the same inherited characteristics How many chromosomes are found in each of the following? Human Cell= 46 (23 pairs) Diploid (2n) Gamete= Sex Cell= 23 (1/2 normal cell!!) Haploid (n) Zygote= Fertilized egg= 46 (23 pairs) Sperm + Egg (n+n=2n) + = (1/2 DNA) (1/2 DNA) 1 whole

9 Where do sex cells come from, since they only have ½ the normal number of chromosomes? Meiosis- Cell division that creates gametes (sex cells) Meiosis converts a diploid cell into a haploid cell

10 Interphase- In-between phase All cells remain in this phase when they are NOT dividing **Right before entering prophase DNA replicates (copies) Prophase I- P -copied DNA pairs up into HOMOLOGOUS PAIRS (find their match = little X s ) -Nuclear membrane disappears -Spindle forms Metaphase I - M -Homologous Pairs meet in the middle

11 Anaphase I- A -Homologous pairs split apart (each side contains Same # of chromosomes as parent cell) -Cell begins to pinch in (cytokenesis) Telophase I- T -2 new cells created with the SAME # of chromosomes as the original cell (Cytokenesis complete; Cell splits) -Nuclear membrane comes back in BOTH cells Meoisis I produces the same end product as (2 Identical Cells with the normal chromosome # )

12 If meiosis produces gametes (1/2 original chromosome #), what happens next??? - A second division MUST occur Meiosis II starts out with 2 cells with Double-Stranded chromosomes It ends with 4 cells with Single-Stranded chromosomes Prophase II- -same as Prophase I occurring in BOTH cells **There is no replication of DNA in Meiosis II -Cells go from Telophase I into Prophase II

13 Metaphase II- Anaphase II- Telophase II At the end of Telophase II: Males: 4 new sperm cells (1/2 of original # chromosomes) Spermatogenesis Females: 1 Egg Cell (3 polar bodies die off) (1/2 of original chromosome #) Oogenesis

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15 1 egg cell produced 4 sperm cells produced

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17 1. Reduces chromosome # Humans (getting ready for fertilization!!!) 2. Variation (genetic differences) What happens if A mistake happens during Meiosis? -Chromosomal Abnormality Ex: Down Syndrome 47 chromosomes

18 Human Karyotype: A picture that pairs up a persons chromosomes by size and shape -Used by Geneticists to study chromosomes and determine genetic disorders Is this a male or a female? -Male (one X chromosome And one Y chromosome)

19 MITOSIS MEOISIS # Cell divisions: # of Daughter Cells Produced: # of chromosomes compared to parent: Same exact # ½ original # Function of cells produced: (Type of cell) Variation: Growth/Repair (Body Cell) NO (Clone) Gamete (sex cell) YES

20 What would each daughter cell look like?

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22 What is the purpose of mitosis? -Growth and repair of BODY CELLS What is the purpose of meiosis? -Produce gametes (sex cells) for fertilization (Reduces chromosome # and creates genetic variation) *** No 2 sperm cells or egg cells are identical!!!

23 Are any two sexually reproducing individuals genetically identical (except identical twins)? -NO!!! -Meiotic Variation Process in which genetic material is exchanged and switched during meiosis causing genetic diversity within a species

24 How does variation occur? 3 Ways: Crossing Over- During meiosis homologous genes are Exchanged between homologous chromosomes

25 Recombination- Due to crossing over, new genes are created that neither parent had

26 Independent Assortment- Every time meiosis occurs, the chromosomes line up in a different order

27 What is the importance of variation? -no two individuals within a species are identical If we were all clones, one disease could wipe us all out!!!! Some advantages to sexual reproduction: -Offspring is not identical to parent (Variation)

28 Why is fertilization important? -transfers genes from BOTH parents to offspring -Restores the chromosome number to normal ONLY occurs in SEXUALLY reproducing organisms Creates gametes (sperm and egg) Creates BODY CELLS for growth and repair of tissue (clones)

29 How do meiosis and fertilization work together to carry out sexual reproduction? -Meiosis reduces the chromosome number by ½, creating gametes (sperm and egg) -Fertilization restores the chromosome # back to normal (sperm + egg = zygote with NORMAL # of chromosomes)