Chapter 6 Sections 1,2 and 6 Pages 166-176; 189-191 MEIOSIS vs MITOSIS Chapter 6 Sections 1,2 and 6 Pages 166-176; 189-191

What are GENES and how do we inherit them from our parents? Has anyone ever told you that you look like your mom or dad? What about your siblings? This happens due to sexual reproduction and the inheritance of your parents genes using sex cells from MEIOSIS!

Important words: Meiosis Genes Gametes Haploid Diploid Crossing over Independent assortment

REVIEW OF MITOSIS Here is what we know about mitosis so far… Used in eukaryotic cells Unicellular = asexual reproduction Multicellular = growth and repair Creates two genetically IDENTICAL somatic cells no genetic variation Body cells (like skin, eyeballs, liver, kidney) - Duplicates DNA to maintain chromosome number

So what is MEIOSIS? MEIOSIS is like mitosis, but it is the process of creating genetically DIFFERENT cells by creating sex cells (gametes). Used for sexual reproduction. Creates four genetically different sex cells! Genetic variation

Meiosis makes sex cells (egg and sperm cells) MALE FEMALE

Meiosis is needed for sexual reproduction Sexual reproduction – the combination of two parent cells using gametes (sex cells) to create genetically different offspring! Like humans and other animals and plants that can reproduce sexually. *Gamete – sex cells; egg and sperm. Haploid – one copy of chromosomes (gametes); n Diploid – two copies of chromosomes. (one from mom and one from dad) ; 2n

BODY CELLS (mitosis) GAMETES (meiosis)

Meiosis and DNA Meiosis makes ½ DNA of the parent sex cell! That way, a sperm cell can combine with an egg cell to form a full set of DNA! ½ DNA from SPERM + ½ DNA from EGG = 1 FULL SET of DNA for OFFSPRING! Or, ½ set from dad + ½ set from mom = full set for child

Compare and Contrast Mitosis and Meiosis BOTH MITOSIS AND MEOSIS Eukaryotic organisms One parent cell Replicates and splits DNA MITOSIS VS. MEIOSIS Genetically identical Body cells (somatic) Makes full set of parent DNA *diploid cells (2n) Takes place all the time Creates 2 daughter cells Asexual reproduction NO crossing over of genes Genetically different Sex cells (gametes) Makes ½ of parent cell DNA *haploid cells (n) Takes place only certain times in life Creates 4 daughter cells Sexual reproduction Crossing over of genes

How do we get genetic variation? Crossing over – this is where some genes will cross over to another chromatid to “change up” the genetic code.

How do we get genetic variation? Independent Assortment – different traits are inherited separately. - the presence of one trait doesn’t affect another - discovered by Gregor Mendel WHY DO CHROMOSOMES INDEPENDENTLY ASSORT AND NOT GENES?

Genes cross over 4 new cells! (egg or sperm)

GROUP PROJECT PART 2: (Page 2) Draw what happens in MITOSIS when your organisms needs to repair and replace its SOMATIC body cells. Be specific with chromosome numbers and stages Show the separation into diploid cells. (Page 3) Draw what happens in MEIOSIS when your organism creates GAMETES. Begin with the correct amount of chromosomes. Show the first separation of cells and the crossing over of genes in color pencil Show the second separation of cells into haploid cells.