Meiosis going from diploid to haploid Making Gametes

Meiosis: going from diploid to haploid Making Gametes: Egg and Sperm. S

The cell cycle remains the same except… G 1 Division: meiosis & cytokinesis G 2 S

Meiosis Overview • Process of nuclear division that reduces the number of chromosomes in new cells to HALF the number in the original cell. • Diploid Haploid

MEIOSIS I S Before Meiosis I happens, the cell will go through interphase: S G 1, S, G 2 (just like Mitosis) 1. Prophase I (crossing over) 2. Metaphase I 3. Anaphase I (homologous chromosomes separate) 4. Telophase I and cytokinesis

Homologous Chromosomes S Both chromosomes have the same traits but different versions of those traits S Paired chromosomes that encode for different versions of the same trait are called homologous chromosomes

Haploid vs. Diploid

Haploid vs. Diploid

Prophase I S Prophase I is the longest and most complex phase. S All of the events that occurred during prophase of mitosis occur + S Homologous chromosomes come together to form a SYNAPSE (TETRAD). S CROSSING-OVER occurs.

Crossing Over: Portions of chromatids break off and attach to adjacent chromatids on the homologous chromosome This allows for more genetic variability! We don’t want everyone to look the same. Ø Occurs during Prophase I

Metaphase I S Homologous chromosomes line up randomly at the center of the cell. We call this independent assortment.

S Instead of all the chromosomes lining up in Metaphase in a single-file line, they will pair up with their homologous partner Mitosis Meiosis

Anaphase I S During anaphase the homologous chromosomes in the center of the cell divide.

Telophase I / Cytokinesis S Telophase I two nuclei form (23 duplicated chromosomes in each) S Cytokinesis occurs resulting in 2 haploid daughter cells.

Meiosis I Interphase Prophase I Metaphase I Anaphase I Telophase I Cytokinesis Images from: http: //www. phschool. com/science/biology_place/biocoach/meiosis/teloi. html

Diploid Haploid

Colorful Karyotypes ✗ ✗ Color the replicated chromosomes from your parents ✗ Maternal – mother ✗ Paternal – father! Remember: your parents received one copy of each chromosome from their parents 20

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Time to figure out your chromosomes! ✗ ✗ ✗ ✗ Flip a coin 22 times If heads, fill in color A If tails, fill in color B If you are a girl: In the box draw and color in an X to match your dad’s X If you are a boy: daw and color in a Y to match your dad’s Y Repeat for the egg: heads – C, tails – D Boy and girls both receive an X from mom (flip a coin to determine C or D) 22

Fill in your karyotype!! S Use the colors from the sperm and egg diagrams S Chromosomes form after egg and sperm unite and chromosomes replicate S Left chromosome – paternal colors S Right chromosome – maternal colors S Don’t forget the XX or XY chromosomes! 23

Tips for a Better Movie S Don’t spend time arguing about what colors to use, but rather focus on making your first cell model and then modify it according to your drawings. S TRY and KEEP CAMERA and ZOOM in the same spot/position/angle as you take each picture. S While one of you gets ready to take a picture, the other team member gets going in moving the parts of the cell. S Be mindful of what else is in the frame to avoid things popping in and out of your video. S Take more pictures than you need. Experiment if flash or no flash works better. S Have fun and be creative! S DON’T FORGET YOUR ID TAG!!!!!!

Meiosis II S Meiosis II comes directly after cytokinesis. No growth (interphase) takes place. S The steps of Meiosis II are identical to mitosis. S DNA is NOT duplicated before Meiosis II

Prophase II S Chromatin condenses into chromosomes S Nuclear envelope breaks down

Metaphase II S Duplicated chromosomes line up in the middle of the cell S Spindle fibers from the centrioles attach to each sister chromatid

Anaphase II S Sister chromatids separate.

Telophase II S Telophase II is the same as telophase in mitosis. S At the end of the second Cytokinesis in Meiosis there are 4 haploid cells Spermatogenesis S Males: 4 sperm S Females: 1 egg + 3 polar bodies Oocyte (oogenesis)

Meiosis II Coming from Meiosis I Prophase II Metaphase II Anaphase II Images from: http: //www. phschool. com/science/biology_place/biocoach/meiosis/teloi. html Telophase II Cytokinesis

Meiosis I Interphase Prophase I Metaphase I Anaphase I Telophase I Cytokinesis Images from: http: //www. phschool. com/science/biology_place/biocoach/meiosis/teloi. html

Meiosis II Coming from Meiosis I Prophase II Metaphase II Anaphase II Images from: http: //www. phschool. com/science/biology_place/biocoach/meiosis/teloi. html Telophase II Cytokinesis

Haploid

Summary of Meiosis I = separates homologous chromosomes Meiosis II = separates sister chromatids

What is the goal of meiosis? S Meiosis 1 S Goal – reduce the chromosome number & mix up the DNA S Meiosis 2 S Goal – separate sister chromatids and form 4 cells

Sexual Reproduction S Involves the fusion of two separate parent cells. S Offspring produced by sexual reproduction inherit some of the genetic information from each parent

Chromosome Mutations S Deletion: entire gene lost S Insertion: entire gene added S Duplication: gene is repeated S Translocation: rearrangement of genes between non-homologus chromosomes S Inversion: segment of

ERROR, ERROR S Non- Disjunction S Sister chromatids fail to separate properly during meiosis II S Failure of a chromosome to separate from its homologue during meiosis S One gamete receives an extra copy of a chromosome and the other gamete lacks the chromosome entirely

Escape Room S With a partner, find answer all the questions S Go to http: //bit. ly/2 m 8 PRTt S Use the answer to solve the puzzles for the final code to escape the room

Choice S Mitosis Worksheet S Phases of Meiosis Worksheet S I Have Who Has Review Cards S Mitosis Taboo S Quizlet – cell cycle