Take out all of your cells. See if you can arrange them in the correct order. Here are some hints: There will be 2 cellular divisions(PMAT) As cells divide they get smaller Which cell would you begin with?

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Comparing Chromosomes in Metaphase Mitosis vs Meiosis In mitosis, the chromosomes align independently of each’s matching chromosome. WHY? However, in meiosis, matching chromosomes form pairs and the pairs align independently. WHY? Because each new cell must receive one of each chromosome. Because this division results in cells with half of the required number of chromosomes.

PI MI AI TI MEIOSIS: cell division to produce the reproductive cells or GAMETES Occurs only in organisms that reproduce sexually Occurs in 2 stages: MEIOSIS I: Results in 2 cells with a reduction by half the total number of chromosomes MEIOSIS II: Results in 4 cells with a division of the chromatids A germ cell forms in testes or ovaries It has the total # of chromosomes referred to as a DIPLOID(2n) cell PI HOMOLOGOUS chromosomes pair forming a TETRAD(4 chromatids) Tetrads are aligned CROSSING OVER occurs and ends of chromosomes are exchanged resulting in new gene combinations MI AI Crossing over is one of several random processes that increase variation in offspring Tetrads are separated TI

NO G1 or S PII MII AII TII The 2 cells that result from meiosis I have half the chromosomes as the germ cell and are HAPLOID(n) NO G1 or S Centrioles divide and reform a new meiotic spindle Two of Mendel’s Laws occur during meiosis: Law of Independent Assortment: homologous chromosomes are aligned randomly during Metaphase I PII MII Law of Segregation Only 1 of 2 chromosomes ends up in each gamete Chromatids are now separated AII TII 4 haploid cells result from meiosis II

Cellular Division to Produce Gametes MEIOSIS Cellular Division to Produce Gametes

Law of Independent Assortment Half of your chromosomes come from one parent and half from the other In independent assortment these maternal and paternal chromosomes are aligned randomly in the tetrad during metaphase I

Law of Segregation When chromatids are separated in metaphase II, only 1 of the two ends up in each gamete This too is a random process

Oogenesis and Spermatogenesis Gamete Formation Oogenesis and Spermatogenesis

Please label the sections below the fold and draw these diagrams SPERMATOGENESIS OOGENESIS Please label the sections below the fold and draw these diagrams Not too small! Fill the space. MEIOSIS I MEIOSIS I MEIOSIS II MEIOSIS II

Now using the two colors you used for crossing over, draw in the SPERMATOGENESIS OOGENESIS Now using the two colors you used for crossing over, draw in the chromosomes

on each of the 4 viable spermatozoa Spermatogenesis Meiosis to produce the male gametes: spermatozoa(sperm) Division of the cytoplasm is equal. All cells same size. MEIOSIS I MEIOSIS II MEIOSIS II Following meiosis a flagella and an enzyme cap are formed on each of the 4 viable spermatozoa

Oogenesis Meiosis to produce the female gametes: ovum(egg) MEIOSIS I Division of the cytoplasm is unequal and which cell receives the most is random. MEIOSIS I The larger cell will become the ovum the smaller cell is called a polar body and is non viable. POLAR BODIES MEIOSIS II MEIOSIS II A polar body’s purpose is to hold chromosomes, they are not viable. POLAR BODY The result of oogenesis is 1 viable ovum and 3 nonviable polar bodies OVUM

M & M Self Evaluation

Necking for Repro rights More won battle To reproduce