Meiosis Gamete Production

MEIOSIS Meiosis is specialized cell division resulting in sex cells with half the genetic material of the parents Sex cells called GAMETES have exactly one set of chromosomes, this state is called haploid (1n) Regular body (somatic) cells have 2 sets of chromosomes, this state is called diploid (2n) and divide through mitosis

(not in notes- write!) Humans have a TOTAL of 46 chromosomes (DNA) in each body cells. For a human baby, you need to pair up the chromosomes. Mom gives haploid cell (N=23) egg, Dad gives haploid cell (N=23) sperm *If a cat’s egg has 10 chromosomes, how many would be found in the diploid cell? *If a dog has 38 chromosomes in the heart cell, how many will be found in the sperm cell?

Meiosis Produce 4 daughter cells with different amount and different type of DNA These cells are Haploid (1n) gamete: sex cells Ex. of gametes are sperm, egg, and pollen Meiosis is for sexual reproduction Sexual reproduction is 2 parents give DNA

Gametes Are Haploid Gametes must have half the genetic material of a normal cell If the genetic material in the gametes was not halved, when they combined the zygote would have more genetic material than the parents. THAT WOULD BE A MUTATION!

*DNA does not replicate again Stages Of Meiosis Meiosis resembles mitosis except that it is actually two divisions not one These divisions are called Meiosis I and Meiosis II Meiosis I Interphase (DNA Replicates) Prophase Metaphase Anaphase Telophase Cytokinesis (2 daughter cells) Meiosis II *DNA does not replicate again Prophase II Metaphase II Anaphase II Telophase II Cytokinesis II (4 HAPLOID daughter cells)

Stages Of Meiosis: Meiosis I Interphase Mother cell Prophase I: Condensing Chromosomes Prophase I: Tetrad formation/ crossing over Metaphase I Anaphase I Telophase I Meiosis II

Stages Of Meiosis: Meiosis II Telophase I Prophase II The products of meiosis are 4 haploid cells each with a unique set of chromosomes. Metaphase II *The products of mitosis are 2 diploid cells with identical chromosomes. Anaphase II Telophase II

Crossing Over Crossing over- A process occurring during meiosis (Prophase I) where two chromosomes pair up and exchange segments of their genetic material. This is how we get genetic variation which means that even though you and siblings have the same parents- you all look different! (except for identical twins)

Crossing Over Prophase I: Metaphase I Anaphase I Telophase I Tetrad formation/ crossing over Metaphase I Anaphase I Telophase I Because of crossing over, every gamete receives a unique set of genetic information. Telophase II

In The Beginning… Two sex cells, a sperm and an egg, unite through the process of FERTILIZATION to form a zygote, the single cell from which the organism develops Meiosis is the process of producing sperm and eggs (gametes) *remember mitosis is to produce body (diploid) cells

Fertilization Results In A Diploid Zygote Egg 1n Haploid nucleus Sperm 1n Haploid nucleus

Fertilization Results In A Diploid Zygote Egg 1n Haploid nucleus Sperm 1n Haploid nucleus

Fertilization Results In A Diploid Zygote Egg 1n Haploid nucleus Haploid nucleus Sperm 1n

Fertilization Results In A Diploid Zygote Egg 1n Haploid nucleus Haploid nucleus Sperm 1n

From Zygote to Embryo Zygote 2n Zygote 2n

From Zygote to Embryo MITOSIS now takes over to make a baby!

From Zygote to Embryo Cleavage

From Zygote to Embryo Cleavage

From Zygote to Embryo Cleavage

From Zygote to Embryo

Compare Mitosis vs. Meiosis Interphase (DNA replicates) Prophase Metaphase Anaphases Telophase (Cytokinesis) Final Product 2 identical cells Same DNA 2 sets of chromosomes Type of cell : Diploid (2N) Body cell Meiosis Interphase (DNA Replicates) Prophase Metaphase Anaphase Telophase Cytokinesis (2 daughter cells) Prophase II Metaphase II Anaphase II Telophase II Cytokinesis II Final Product 4 gamete different cells Mixed DNA 1 set of Chromosomes Type of cell: Haploid (N) gamete/sex cell

When does mitosis occur. What kinds of cells are produced When does mitosis occur? What kinds of cells are produced? When does meiosis occur? What kinds of cells are produced?

Video Amoeba sisters: Meiosis

The End