Warm-Up Decide if the people in the pictures are related or not.

Review Catalyst: Mitosis 1) Is mitosis an example of sexual or asexual reproduction? Why? 2) Why would it be a bad thing if you were an EXACT copy/clone of your mom or your dad? Asexual vs. Sexual Reproduction Asexual = reproduction done by only 1 organism by either cloning or splitting itself Sexual = reproduction done by 2 organisms of opposite sex; requires egg and sperm

Mitosis Review Form of ASEXUAL reproduction Daughter cells IDENTICAL to parent t cells Same number of chromosomes

Somatic (body) cells All human body cells have _______ chromosomes. o Reminder: chromosomes are coiled-up DNA Every cell MUST have the exact same amount of chromosomes. Check for Understanding: How many chromosomes in… 1) Liver Cell ___ 2) Lung Cell ____ 3) Bone Cell ___ 4) Brain Cell ____ 46

All chromosomes in your somatic cells are found in pairs How many total chromosomes? How many pairs of chromosomes? Human Skin Cell These pairs are called homologous chromosomes

Homologous: same Homologous chromosomes: Chromosomes that are the SAME length and carry the same traits (hair, eye color, skin type). Similar, but not identical! ONE STRAND FROM MOM ONE STRAND FROM DAD

New Vocabulary: Every somatic cell is said to be a DIPLOID cell DIPLOID - a cell with 2 sets of chromosomes (2n) (half from mom and half from dad) For humans, every DIPLOID cell has 46 chromosomes.

DIPLOID somatic cell (skin cell)

Haploid: a cell that has only ½ the chromosomes of a diploid (1n) Example: Sex Cells are HAPLOID CFU If a diploid cell has 46 chromosomes, how many chromosomes would a haploid have? 23 chromosomes

HAPLOID (Think HALF) Sex Cells are Haploid Cells

Sexual Reproduction In sexual reproduction two haploid SEX cells come together to form a diploid cell. These cells are also called _________________ Male sex cell: ____________ Female sex cell: ____________ Gametes Sperm Eggs An egg fertilized with sperm produces an offspring called a Zygote How many chromosomes? ________ 23 46

Diagram!

How are sex cells created? Sex cells (gametes) are CREATED through the process of meiosis.

Check For Understanding The human zygote has 46 chromosomes. Based on this information, how many chromosomes are in EACH sex cell? 23 This means that you get 23 chromosomes from you mother and 23 chromosomes from your father!

Check for Understanding! For each of the following types of cells, hold up 2 fingers if it is diploid and hold up 1 finger if it is haploid. 1.Bone cells 2.Kidney Cells 3.Sperm 4.Muscle cells 5.Tongue Cells 6.Egg Diploid Haploid Diploid Haploid

Check for understanding: 1.If the egg of a fruit fly has 8 chromosomes and the sperm of a fruit fly has 8 chromosomes…..How many chromosomes will the zygote have? 2.If a zygote of a zebra has 12 chromosomes, how many will EACH sex cell have? 16 6

Master the Vocab!! You have 5 min.

How are sex cells (with only 23 chromosomes in them) created? Meiosis Don’t get this confused with MITOSIS. Occurs in 2 phases: 1) Meiosis I 2) Meiosis II Results in 4 cells with HALF the chromosomes of the original cell

Crossing Over Crossing over is the major event that occurs in meiosis Crossing over: Chromosomes exchange parts to mix up the DNA. The result is: New Gene Combinations!!

Continued This produces genetic diversity: the differences in a species…. THIS IS WHY WE ALL LOOK DIFFERENT! The major advantage of sexual reproduction: Genetic Variation

Diagram!

Lets review! 1.How many cells exist at the beginning of meiosis? 2.How many cells exist at the end of meiosis? 3.How many chromosomes does the human parent cell have? Diploid or Haploid? 4. What happens in S phase? 1 cell 46 Diploid DNA Replication (DNA doubles)…each chromosome makes a copy of itself 4 cells Diploid or Haploid? Diploid Haploid

Meiosis Animation E&feature=relatedhttp:// E&feature=related Meiosis Square Dance feature=related

Recap: Meiosis Similar to mitosis in SOME ways o Division of cells o PMAT DIFFERENT in MANY ways o Involves 2 cell divisions instead of 1 (homologous chromosomes) o Results in 4 cells with ½ the genetic information (HAPLOID cells) called GAMETES