Meiosis Blueprint of the Body 1 blueprint from

Meiosis

Blueprint of the Body 1 blueprint from your dad and 1 blueprint your mom

Homologous Chromosomes You have a copy of each gene from your mom and your dad What is a gene? A gene is a sequence of DNA that codes for a trait

Homologous chromosomes Homologous: same • Homologous chromosomes: Chromosomes of the same length with the same gene types, but 1 is from the mother and 1 is from the father • Similar, but not identical!

Mitosis Review What is the purpose of mitosis? Growth! Repair! Mitosis produces 2 daughter cells that are genetically IDENTICAL to the parent cell Only occurs in somatic cells (body cells)

Mitosis Review Form of ASEXUAL reproduction Daughter cells IDENTICAL to parent cells

Mitosis: Which stage? Which stage is this? How do you know? What are the chromosomes doing? Has the DNA been duplicated at this stage?

Vocabulary • Diploid (2 N): normal amount of genetic material in eukaryotic cells • TWO copies of each gene • Haploid (N): ½ the genetic material usually found in cells • Only ONE copy of each gene

Vocabulary Application Mitosis begins with 1 DIPLOID cell and produces two DIPLOID cells identical to the parent cell

Meiosis

Meiosis Purpose of meiosis: Sexual reproduction Create gametes (reproductive cells)

Meiosis Similar to mitosis in SOME ways Division of cells PMAT • DIFFERENT in MANY ways • Involves 2 cell divisions instead of 1 • Creates gametes instead of somatic cells • Results in haploid cells

Meiosis in Humans In humans, these haploid cells (gametes) are the ova (egg) and sperm

Meiosis Occurs in 2 phases: Meiosis II

Meiosis I

Meiosis I: Interphase I DNA replicates! Amount doubles

Meiosis I: Prophase I Crossing over. Genetic material from maternal and paternal chromosome mix up This creates genetic variation!

Meiosis I: Metaphase I Homologous chromosomes line up in the middle (the metaphase plate)

Meiosis I: Anaphase I Fibers pull homologous chromosomes toward opposite ends of the cell

Meiosis I: Telophase I New nuclear envelopes develop around homologous chromosomes at opposite poles

Meiosis I: Cytokinesis I The cell membrane pinches inward splitting the cell in half – forms two new cells

Meiosis I Interphase I Prophase I Metaphase I Anaphase I Telophase I and Cytokinesis

Meiosis II: Prophase II NO INTERPHASE II— chromosomes are NOT replicated Each of the cell’s chromosomes has 2 chromatids

Meiosis II: Metaphase II Chromosomes the cell line up at the center of

Meiosis II: Anaphase II The sister chromatids pull apart

Meiosis II: Telophase II The sister chromatids move toward opposite ends of the cells Nuclear envelopes (membranes) develop around chromosomes at each pole

Meiosis II: Cytokinesis II The cells divide into 4 haploid cells

Meiosis II Telophase I and Cytokinesis I Meiosis II Prophase II Metaphase II Anaphase II Telophase II and Cytokinesis

Checkpoint! Vocabulary What review: is a homologous chromosome? What is a diploid cell? What is a haploid cell?

Checkpoint! Put 1 finger up for MITOSIS. Put 2 fingers up for MEIOSIS. Which process creates 2 daughter cells? Which process has 2 stages? Which process creates gametes? Which process results in genetic variation?

Checkpoint! Humans How have 46 chromosomes many chromosomes are in somatic (diploid) cells? How many chromosomes are in gamete (haploid) cells)?

Meiosis Animation http: //highered. mcgraw- hill. com/sites/0072495855/student_view 0/cha pter 28/animation__how_meiosis_works. html

Mitosis vs. Meiosis Mitosis Meiosis Results in 2 diploid Cells (2 N) 4 haploid cells (N) Cells are Genetically identical Genetically different Occurs in Somatic cells (body cells) Sex cells (gameteseggs and sperm cells)