WARM Up Write everything you know/remember about mitosis

Meiosis Gamete Production Texas Expected Knowledge and Skills (TEKS) 6G Recognize the significance of meiosis to sexual reproduction

Somatic Cells (Body Cells) MEIOSIS Meiosis is specialized cell division resulting in sex cells with half the genetic material of a body (somatic) cell. The process of making sperm and eggs (gametes). Somatic Cells (Body Cells) Gametes (Sex Cells) Full set of chromosomes – Diploid (2n)   Divide via Mitosis (cell cycle) Half a set of chromosomes – Haploid (1n) Divide via Meiosis

Humans have a TOTAL of 46 chromosomes (condensed DNA) in each body cell. For a human baby, mom gives a haploid egg (n=23) and dad gives a haploid sperm (n=23) to make a full set of 46 chromosomes.

Questions *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 Produces 4 daughter cells with diverse genetic chromosomes (DNA). These daughter cells are Haploid (1n) gametes: sex cells Examples: sperm, eggs, pollen Meiosis is for: sexual reproduction Sexual reproduction includes 2 parents contributing DNA.

Gametes must have half the genetic material of a body cell If the genetic material in the gametes were not halved when they combined, the resulting offspring would have more genetic material than the parents. This would be a MUTATION! Mule Zedonk

Process of Meiosis During Meiosis, a cell divides twice, but only replicates its DNA once. This leads to four daughter cells with half the amount of genetic information.

Crossing Over During meiosis chromosomes pair up and exchange segments of their genetic material in a process called crossing over.

Crossing Over Crossing over leads to genetic variation. Crossing over is why siblings can have the same parents but still may look very different (except for identical twins etc.).

Question What is the significance of crossing over to a population? Explain your answer

In The Beginning… Fertilization: the process of two sex cells, a sperm and an egg, uniting. Zygote: a single cell formed from the union of a sperm and egg which leads to a unique individual.

Fertilization Results In A diploid cell, a zygote Egg n Haploid nucleus Sperm n Haploid nucleus

Fertilization Results In A diploid cell, a zygote Egg n Haploid nucleus Sperm n Haploid nucleus

Fertilization Results In A diploid cell, a zygote Egg n Haploid nucleus Sperm n Haploid nucleus

Fertilization Results In A diploid cell, a zygote Egg n Haploid nucleus Sperm n Haploid nucleus

From Zygote to Embryo Zygote 2n Zygote 2n

From Zygote to Embryo Once fertilization occurs, mitosis takes over allowing the cell to divide and grow into a unique individual.

From Zygote to Embryo Cleavage

From Zygote to Embryo Cleavage

From Zygote to Embryo Cleavage

From Zygote to Embryo

Identical Twins Formed from one egg and one sperm. Before the cells differentiate into specific types of cells, a clump of cells splits off from the whole group. Both clumps will then differentiate into separate individuals with the same genetic makeup.

Identical Twins

Fraternal Twins Formed from two eggs and two sperm. Non-identical siblings who are born at the same time.

Compare Mitosis vs. Meiosis Final Product 2 identical cells Same DNA Full set of chromosomes Type of cell : Diploid (2N) Body cell Meiosis Final Product 4 gamete different cells Mixed DNA Half set of Chromosomes Type of cell: Haploid (N) gamete/sex cell

Answer the following questions: When does mitosis occur Answer the following questions: 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