Meiosis Make a cover page: Your Name Chapter 11 Meiosis Feel free to decorate your cards as you go!

Diploid –2 sets of chromosomes in a cell. –½ from mom, ½ from dad. –2n –All body cells are diploid. –Made by MITOSIS. Haploid –1 set of chromosomes in a cell. –1n –All sex cells are haploid. –Made by MEIOSIS. (2 separate flashcards)

DIPLOID vs. HAPLOID 1n + 1n = 2n egg + sperm = new organism Haploid + Haploid = DIPLOID Not a flashcard.

Gametes Another name for sex cells: egg & sperm

Zygote A fertilized cell. 2 gametes that are now together.

In case you’ve never seen it for real…this is human DNA. Not a flashcard.

23 Homologous pairs – one from mom and one from dad This is a DIPLOID cell’s DNA. (2n) Not a flashcard. To do this, MITOSIS is used.

This is a HAPLOID cell’s DNA. (1n) Not a flashcard. To do this, MEIOSIS is used.

Meiosis The making of gametes (eggs & sperm). Cells contain ½ the normal amount of chromosomes. (haploid)

Meiosis

Why is meiosis necessary? If the sex cells didn’t have ½ the amount of chromosomes, what would happen when the sperm & egg made a zygote? Answer: Each baby would have twice the number of chromosomes as the parents!!! 26 + = 52! egg sperm zygote WOW! That’s 2 full sets!

What is produced in meiosis? 4 haploid cells (1n) Each cell is genetically different! Cool!

The cells produced during meiosis have DIFFERENT DNA! Not a flashcard.

Review Meiosis Facts Makes ____ cells genetically different from parent cell & from each other Makes _____ cells (1n or 2n?) Makes ________________ Used for ______________ 4 1n Gametes (sperm & eggs) sexual reproduction Not a flashcard.

Spermatogenesis Makes 4 sperm cells.

Oogenesis Makes 1 egg. (and 3 polar bodies)

Spermatogenesis vs. Oogenesis Not a flashcard.

What is different about meiosis? Many different variations in the gametes. ___________________________________ Divides twice, but only copies DNA once. ___________________________________ Makes cells with different genes than parent cell Makes cells with ½ the number of chromosomes as parent cell Not a flashcard.

Phases of Meiosis I P M A T P M A T Meiosis 1 Meiosis 2 (I Peed on the MAT twice!)

Meiosis

I P M A T P M A T cytokinesis

Mitosis vs Meiosis Interphase Interphase I DNA spread out as chromatin Nuclear membrane visible DNA copied during S phase Same as mitosis!

Mitosis vs Meiosis Prophase Prophase I DNA scrunches into chromosomes Nuclear membrane disappears Centrioles appear Same, except… Homologous pairs match up XX XXXXXX

Crossing Over Chromatid arms trade DNA with each other. Produces daughter cells with different gene combinations.

Mitosis vs Meiosis Metaphase Metaphase I Chromosomes line up in middle Chromosomes line up in middle with homologous partner

Mitosis vs Meiosis Anaphase Anaphase I Chromatids split and move apart. Chromatids stay together Homologous pairs move apart

Mitosis vs Meiosis Telophase Telophase I Two nuclei Nuclear membrane returns DNA spreads out as chromatin Same as mitosis!

Mitosis vs Meiosis Cytokinesis Cytokinesis I Cytoplasm splits into 2 cells Same as mitosis!

Mitosis vs Meiosis Prophase Prophase II DNA scrunches into chromosomes Nuclear membrane disappears Centrioles appear Same as mitosis!

Mitosis vs Meiosis Metaphase Metaphase II Chromosomes line up in middle Same as mitosis!

Mitosis vs Meiosis Anaphase Anaphase II Chromatids split and move apart Same as mitosis!

Mitosis vs Meiosis Telophase Telophase II Two nuclei Nuclear membrane returns DNA spreads out as chromatin Same as mitosis!

Mitosis vs Meiosis Cytokinesis Cytokinesis II Cytoplasm splits Same as mitosis!

Mitosis vs Meiosis In Meiosis: (Prophase I) Homologous pairs match up. (Prophase I) Crossing over creates genetic differences. Cells divide twice but only copies DNA once- this makes haploid cells.

Meiosis

The end. Really. Test date: How to succeed on GHS biology tests: –Memorize the flashcards. Practice with friends, by yourself, or with family. –Read the book. It is easy reading. Reading the text helps you understand the written part. –Do all labs, homework, and worksheets. If you missed any days, make sure you made up any work!