Review: 1. What is mitosis? 2. What are the stages of mitosis? Process of Cell Division Prophase, Metaphase, Anaphase, Telophase

Review: 3. How many cells are created through this process? 4. What types of cells are made? 2 cells Identical Somatic Diploid cells

Today’s Target I can describe, draw, and explain the steps of how gametes (sex cells) are formed. I can explain how the daughter cells in meiosis are all different I can compare and contrast between somatic cells and gametes

INTERPHASE In nucleus

MITOSIS Begin with a Diploid Cell 2N = 4

MITOSIS Chromosomes are in a single file line

MITOSIS Centromere divides Sister chromatids move apart

MITOSIS End with two Diploid Cells that are identical

◦Begin with 1 somatic Diploid (2N) cell MITOSIS ◦4 phases: ◦Prophase ◦Metaphase ◦Anaphase ◦Telophase ◦End with 2 Identical Diploid (2N) cells

Meiosis The process by which Gametes are formed Gamete: ◦Sperm or Egg ◦Haploid: One set of chromosomes ◦(Only mom or dad) ◦In eukaryotic cells, this means that gametes have HALF the number of chromosomes as Diploid cells

MEIOSIS

Homologous chromosomes form tetrads at the equator = pair of homologous chromosomes

MEIOSIS Homologous chromosomes move AWAY to the poles

MEIOSIS 2 cells so far

MEIOSIS

Chromosomes align at the equator NOW … single file line equator

MEIOSIS Centromeres divide

MEIOSIS End with 4 Haploid Cells All are different n = 2

4 Sperm Cells

1 Egg Cell

Meiosis Notes 1. Similar to Mitosis 2.Divides twice = Meiosis I : Meiosis II **** 8 phases total ****

Meiosis: Two Part Cell Division 22 Meiosis I Meiosis I Meiosis II Diploid Haploid

Meiosis… …Occurs in Sex Organs (ovaries and testes) … Produces 4 cells with half of the genetic material (Haploid cells)

Meiosis… …in Humans: Gametes = sperm (23) and egg (23) Zygote = fertilized egg (46)

Fertilization Gamete

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

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

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

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

From Zygote to Embryo Zygote 2n Zygote 2n

Homologous Chromosomes exchange DNA ◦Increases variation in a species ◦Occurs during Prophase I of Meiosis I Crossing Over

Crossing over Exchange of genes

MEIOSIS Homologous chromosomes move AWAY to the poles

Crossing Over

Homologous Chromosomes Match up the homologous chromosomes

Crossing Over Advantages - Genetic Variation - Higher survival rate in a changing environment

Mitosis Vs. Meiosis PROPHASEPROPHASE I

Mitosis Vs. Meiosis METAPHASEMETAPHASE I

Mitosis Vs. Meiosis ANAPHASEANAPHASE I

Mitosis Vs. Meiosis TELOPHASETELOPHASE I

Mitosis Vs. Meiosis CYTOKINESIS

Mitosis Vs. Meiosis PROPHASE II

Mitosis Vs. Meiosis METAPHASE II

Mitosis Vs. Meiosis ANAPHASE II

Mitosis Vs. Meiosis TELOPHASE II

Create a Venn diagram to compare and contrast MITOSIS MEIOSIS

Gametes Crossing over 2 cells 4 cells 1 cycle of PMAT 2 cycles of PMAT Haploid cells DNA replicated only once Cellular reproduction Genetically different cells Somatic cells sperm cells Interphase occurs before Sex cells 2N 46 chromosomes 23 chromosomes Asexual Sexual N Body Cells Cells are identical

Mitosis vs. MEIOSIS mitosis meiosis Somatic cells Cells are identical 2N 46 chromosomes Asexual Body cell 2 cells 1 cycle of PMAT Gametes Crossing Over 4 cells 2 cycles of PMAT Haploid Sex cells 23 chromosomes N Sperm cell sexual DNA replicates only once Cellular Reproduction Interphase occurs before

12 24 yes no 4623 no yes 11

Half the number of chromosomes n2n Body Cell (somatic) Sex Cells (gametes) Both sets of chromosomes