DNA and Mitosis review/Meiosis How do your cells divide? This PowerPoint has many animated slide progressions. You may only want to print the following slides: 1-11, 14-15, 22-47

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) Haploid – number of chromosomes in sex cells represented by n indicating one chromosome Diploid - number of chromosomes in somatic cells represented by 2n indicating a set or double number of chromosomes

A Cell’s Life Interphase Have students notice that the majority of a cell’s life is spent in interphase and during that time, the cell is performing all it’s cellular processes needed to survive. Indicate that M is Mitosis, the small amount of time the cell spends dividing. Picture taken from http://www.sol.duke.edu/mitosis/cycle/

Why Do Cells Divide? Growth Damaged cells Sex cells Answers are animated so you can ask students the question before you reveal the answers Maintain workable surface area to volume - too big-can’t work!! Replace damaged cells Produce sex cells Sex cells

Cell Reproduction is either sexual or asexual

Asexual Reproduction (one parent) Binary Fission- Budding Vegetative Propagation Regeneration Advantages? Binary Fission - split in two (bacteria) Budding- (Yeast) Vegetative Propagation - (Plants) Regeneration - Disadvantages?

Asexual reproduction Advantages: Disadvantages: 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

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

DNA Replication Before a cell can divide the DNA must replicate (make a copy of itself)

DNA Replication Making a new strand of DNA is actually quite easy. Replication occurs in 3 easy steps…

1. DNA Unzips An enzyme (helicase) unzips the molecule The enzymes breaks the hydrogen bonds that hold the nitrogen bases together.

DNA Replication DNA Unzips G T C This animation of DNA unzipping will proceed on it’s own

DNA Replication DNA Unzips G This animation of DNA unzipping will proceed on it’s own

DNA Replication DNA Unzips G This animation of DNA unzipping will proceed on it’s own

DNA Replication DNA Unzips G This animation of DNA unzipping will proceed on it’s own

DNA Replication DNA Unzips G This animation of DNA unzipping will proceed on it’s own

DNA Replication DNA Unzips G This animation of DNA unzipping will proceed on it’s own Left Strand of Original DNA Right Strand of Original DNA

2. Base Pairing Complementary bases match with each DNA strand in the open helix DNA polymerase

DNA Replication Base Pairing Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA

DNA Replication Base Pairing Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand

DNA Replication Base Pairing Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand

DNA Replication Base Pairing Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand

DNA Replication Base Pairing Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand New Left DNA Strand

DNA Replication Base Pairing Left Strand Original DNA This animation of DNA pairing up will proceed on it’s own Right Strand Original DNA New Right DNA Strand New Left DNA Strand

DNA Replication Base Pairing Left Strand Original DNA Have students notice that there are two strands of DNA that are exactly alike Right Strand Original DNA New Right DNA Strand New Left DNA Strand

3. DNA Zips Up An enzyme (ligase) zips the new molecules back up.

DNA Replication Voila! Two identical strands of DNA! T C A G

DNA Replication Review Step 1 Step 2 Step 3 Step 1 – DNA unzips Step 2 – Complementary bases match with each DNA strand in the open helix Step 3 – DNA zips up

Remember - All this takes place in INTERPHASE

Now that DNA has replicated, we are ready to begin Mitosis (nucleus of the cell divides) Remind students Mitosis is an asexual cellular reproduction T C A G T C A G

Interphase: Parent Cell, chromosomes replicated Prophase: Chromatin condenses into chromosomes, nuclear envelope disappears, centrioles move to opposite poles, spindle fibers form. Metaphase: Chromosomes align on the equator Have students look at the pictures and try to figure out what is happening to the DNA in each. The slide is animated so you can ask the questions and reveal the answers when you are ready Anaphase: Chromosomes separate and chromatids are pulled to opposite poles Telophase: DNA uncoils, nuclear membrane reappears

Cytokinesis Cleavage (indention in cell membrane) or cell plate formation occurs. Cell divides. Cytokinesis almost always follows mitosis. This is what creates two separate cells. Ask students what would happen if you have mitosis without cytokinesis (one cell with two nuclei). Animal Cell Plant Cell

Mitosis Animation This animation is a review of mitosis. Have students review what is happening to the chromosomes. Animation from http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_gif1.html

It’s all about the chromosomes! There are 46 in human body cells The number of chromosomes remain constant during Mitosis Very important to emphasize that the number of chromosomes during mitosis remain constant.

Which Cells Go Through Mitosis? Somatic (body) cells: Cells which help the body in: Growth Repair Explain the reason the chromosome number remains the same is because Mitosis is producing somatic cells (Skin, hair, muscle, etc.) Work

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)? Questions are animated so you can ask each question and get an answer before going to the next question.

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? Questions are animated so you can ask each question and get an answer before going to the next question. 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 Meiosis is the production of sex cells (gametes). During meiosis, the number of chromosomes in the daughter cells are reduced from the number of chromosomes in the parent cell (this is extremely important).

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? Animation of meiosis to use as a review Meiosis Animation from http://biology.clc.uc.edu/courses/bio104/meiosis.htm

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

Meiosis Review Is the beginning parent cell diploid or haploid (2n or n)? 2. Are the resulting daughter cells diploid or haploid (2n or n)? Questions are animated so you can ask each question and get an answer before going to the next question.

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? 6. How many chromosomes are in a human parent cell? Questions are animated so you can ask each question and get an answer before going to the next question. 7. How many chromosomes are in a human daughter cell?

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

Fertilization Mom Dad 23 46 New Individual 23 Formation of a new individual through the union of parent cells The number of chromosomes are animated so you can ask students the answers before it comes up New Individual 46

This is how new organisms are made!!

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

Let’s review Mitosis & Meiosis

Visual review of the differences between mitosis and meiosis

Mitosis vs. Meiosis √ √ √ √ √ √ Event Mitosis Meiosis Produces 4 cells   Mitosis vs. Meiosis Event Mitosis Meiosis 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 √ √ √ √ The answers are animated so you can have students answer the question before you reveal the answer. √ √

Mitosis vs. Meiosis √ √ √ √ √ Event Mitosis Meiosis   Mitosis vs. Meiosis Event Mitosis Meiosis Beginning cells diploid (2n) Beginning cells haploid (n) Ending cells diploid (2n) Ending cells haploid (n) Produces egg and sperm Produces body cells √ √ The answers are animated so you can have students answer the question before you reveal the answer. √ √ √