DNA and Mitosis review/Meiosis How do your cells divide?

A few words before we start….. Haploid: half of a full set (only 1 set of DNA) Diploid: full set (1 set from each parent (2 sets)

A Cell’s Life

Why Do Cells Divide? Growth Damaged cells Sex cells

Cell Reproduction is either sexual or asexual

Asexual Reproduction (one parent) Binary Fission- Budding Vegetative Propagation Regeneration Advantages? Disadvantages?

Asexual reproduction Advantages: – Doesn’t require a mate – Takes less time Disadvantages: – All offspring are the same (genetically)

Sexual Reproduction 2 “parents” or 2 sets of DNA Examples: humans, plants, dogs

Advantages – DIVERSITY!!!!!!!!!! Offspring are genetically different from parents. Disadvantages? – Need a mate – Takes longer Sexual reproduction

Mitosis Animation

Mitosis Review 1. Is the beginning parent cell diploid or haploid (2n or n)? 2. Are the daughter cells diploid or haploid (2n or n)?

More Mitosis Review 3. How many daughter cells are produced? 4. Are the resulting daughter cells different from the parent cell?

More Mitosis Review 5. Are the resulting daughter cells different from each other? 6. How many chromosomes are in a human parent cell? 7. How many chromosomes are in a human daughter cell?

More Mitosis Review 8.What types of cells are produced by mitosis? 9. Why (when) does a cell go through mitosis?

Meiosis Sexual Reproduction (two parents)

Why Meiosis? Meiosis - – The production of gametes

Interphase Cell growth DNA replication  sister chromatids held together by centromere

Prophase I The chromosomes coil up and a spindle forms. Homologous chromosomes line up with each other gene by gene along their length, to form a four-part structure called a tetrad.

Prophase I – crossing over Crossing over occurs between homologous chromosomes  new genetic combinations that are different from the parent.

Metaphase I The spindle fibers pull the tetrads into the middle, or equator of the cell. There is no rule to who is on left or right side  independent assortment.

Anaphase I Homologous chromosomes separate and move to opposite ends of the cell.

Telophase I The spindle is broken down, the chromosomes uncoil slightly, and the cytoplasm divides to yield two new cells. Each cell has half the DNA as the original cell because it has only one chromosome from each homologous pair.  Haploid

Remember mitosis? Meiosis II looks just like mitosis except there is no DNA replication during interphase

Prophase II A spindle forms in each of the two new cells and the spindle fibers attach to the chromosomes.

Metaphase II. Sister chromatids, are pulled to the center of the cell and line up randomly at the equator.

Anaphase II The sister chromatids separate and move to opposite poles.

Telophase II Finally nuclei reform, the spindles breakdown, and the cytoplasm divides. Four haploid cells have been formed from one diploid cell – All are genetically different from each other and from the parent cell.

How does Meiosis Occur?

Why meiosis is important 1.Forms gametes for sexual reproduction 2.Crossing over and independent assortment  different genetic combinations.  diversity!!!

Meiosis Review 1.Is the beginning parent cell diploid or haploid (2n or n)? 2. Are the resulting daughter cells diploid or haploid (2n or n)?

More Meiosis Review 3. How many daughter cells are produced?  Are the resulting daughter cells different from the parent cell?

More Meiosis Review 5. Are the resulting daughter cells different from each other? 7. How many chromosomes are in a human daughter cell? 6. How many chromosomes are in a human parent cell?

More Meiosis Review 8. What types of cells are produced by meiosis?

Fertilization New Individual 46 Mom 23 Dad 23

This is how new organisms are made!!

Sexual reproduction Meiosis Sperm Cell Egg Cell Haploid gametes (n=23) Fertilization Diploid zygote (2n=46) Mitosis and Development Multicellular diploid adults (2n=46)

Let’s review Mitosis & Meiosis

Mitosis vs. Meiosis EventMitosisMeiosis Produces 4 cells Produces 2 cells New cells identical New cells different New cells have the same number of chromosomes as parent New cells have fewer chromosomes than parent √ √ √ √ √ √

Mitosis vs. Meiosis EventMitosisMeiosis Beginning cells diploid (2n) Beginning cells haploid (n) Ending cells diploid (2n) Ending cells haploid (n) Produces egg and sperm Produces body cells √ √ √ √ √ √