Mitosis and Meiosis CELL DIVISION

Mitosis and Meiosis Mitosis: -division of somatic (body) cells - Exact copy of cell (2N or Diploid) -Takes place in all cell types of the body (growth, repair, replacement) Meiosis -division of gametes (sex cells) -Not exact copy of cell (N or Haploid) - Meiosis only takes place in organisms that reproduce sexually ___________________________________ ____

ARE you Tracking? These questions are not in your notes This type of cell division ONLY takes place in the gonads (sex organs) -Meiosis- produces sex cells Are the sex cells haploid or diploid? Haploid or N cells are only found in sex cells (humans sex cells would contain 23 chromosomes) When a root grows from 3cm to 6 cm, this type of cell division is responsible: -MiTosis with a T. MiTosis produces Two N cells. All growth is the result of MiTosis

How many chromosomes would be in a human nerve cell? 46 Chromosomes or Diploid (2N) How many chromosomes would be in a human bicep muscle? 46 Chromosomes or Diploid (2N) How many Chromosomes would be in the fingernail cells of your right index finger? 46 Chromosomes or Diploid (2N) How many chromosomes would a human egg or sperm contain? 23 Chromosomes or Haploid (N)

The haploid sperm and haploid egg fuse to produce a fertilized egg with how many chromosomes? 46 Chromosomes or Two N What type of cell division results in the fertilized cell (Zygote) dividing into two cells, 4 cells, 8 cells …1,000 cells? Mitosis with a T. All of the new cells in the developingZygote are diploid

Mitosis Interphase Prophase Metaphase Anaphase Telophase

Interphase Interesting things happen! 1.Cell preparing to divide 2.Genetic material doubles

Prophase Chromosome pair up! 1.Chromosomes thicken and shorten -become visible -2 chromatids joined by a centromere 2.Centrioles move to the opposite sides of the nucleus 3.Nucleolus disappears 4.Nuclear membrane disintegrate

Metaphase Chromosomes meet in the middle! 1.Chromosomes arrange at equator of cell 2.Become attached to spindle fibres by centromeres 3.Homologous chromosomes do not associate

Anaphase Chromosomes get pulled apart 1.Spindle fibres contract pulling chromatids to the opposite poles of the cell

Telophase Now there are two! 1.Chromosomes uncoil 2.Spindle fibres disintegrate 3.Centrioles replicate 4.Nucleur membrane forms 5.Cell divides

Meiosis Only takes place in the gonads or sex organs 4 daughter cells produced Each daughter cell has half the chromosomes of the parent Haploid Cells = N 2 sets of cell division involved

Does Meiosis take place in organisms that only reproduce sexually ? No. Meiosis only takes place in organisms that reproduce sexually by using sex cells. What are the ONLY cells in a human body that are not produced by Mitosis with a T? The sex cells and they are produced through Meiosis.

Sexual Reproduction Takes two parents to reproduce Each Parent contributes one sex cell to produce a Zygote Sexual reproduction results in much greater genetic variation in Offspring This genetic variation increases the odds that a population can survive when the environment changes Where does this variation come from?

1. Increased Variation through Independent Assortment during Meiosis

2. Increased Variation through Crossing Over during Meiosis You would think one Gamete would contain either one maternal chromosome or one paternal chromosome, but not both. Crossing Over produces recombinant chromosomes during meiosis which combines genes inherited from both of our parents on one chromosome.

Crossing Over

3. Increased Variation through The Random Nature of Fertilization An Ovum (egg) represents approximately 8 million possible different chromosome combinations A Sperm cells represents approximately 8 million possible chromosome combinations Think about that for a few seconds All of those possible combinations is what makes us unique and makes us different from our parents and our siblings. It is this variation in organisms that is the fuel for evolution

Asexual Reproduction Organisms that reproduce Asexually (takes only one parent) produce an exact copy of themselves An exact copy can be called a clone This greatly reduces the variation that is in a population. One disease or a change in the environment can wipe them all out. Has potential advantages in stable advantageous environment

Asexual Reproduction-Budding Fission is an equal division Budding is an unequal division

Fragmentation and Regeneration

Asexual Reproduction- Vegetative Propagation Vegetative propagation-is development of a new plant from a stem, root, leaf of the parent plant.

Asexual Reproduction- Strawberry runners Quack Grass

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