With your partner, discuss the following questions: 1.Are you taller? Did your hair grow? Did you clip your toenails? 2.Have you broken a bone? 3.How does your body repair itself? 4.How does a human being grow from a single fertilized cell into an individual containing billions of cells? 5.Do all the cells of the body look the same? Do they all perform the same function? 6.Do all the cells of the body contain the same genetic information?

Mitosis Videos: The Mini Mitosis Tutorial BrainPOP Mitosis Video

Cell Cycle How do baby elephants grow up to be big elephants?

Why do organisms need more cells?

Why do organisms need new cells? When you are growing! When you need to replace damaged cells!

How do cells make new cells? smaller nutrientsgrow All cells are created from other cells. The only way to get more cells is for cells to divide. Cell division is the process by which a parent cell divides into two or more daughter cells (IDENTICAL CELLS!). The parent cell provides the genetic code to each daughter cell.

Identical Daughter Cells Identical Daughter Cells Parent Cell Two identical daughter cells

interphase Cell Cycle In order for new somatic (body) cells to be made, they must go through the cell cycle: Interphase Mitosis

interphase Interphase Before dividing, cells spend most of their time finding nutrients and growing. This phase is called interphase. During interphase, there are two growth phases. These are known as G 1 and G 2.

DNA replication occurs during the synthesis (S) phase of interphase. Interphase - DNA Replication

Why Replicate? Remember: ALL cells need genetic material….DNA! So….before a cell can divide, the DNA must be replicated (copied). If a cell doesn’t get a copy of DNA, it is USELESS and essentially DEAD!

DNA Replication DNA → DNA (copy) DNA is a HUGE molecule, in fact it is so HUGE it cannot exit the nucleus EVER ! Sooo… DNA Replication occurs in the NUCLEUS!

3 EASY STEPS STEP 1: ◦DNA Unzips ◦DNA Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds 5’ 3’

STEP 1: ◦DNA Unzips ◦DNA Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds 3 EASY STEPS

STEP 1: ◦DNA Unzips ◦DNA Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds 3 EASY STEPS

STEP 1: ◦DNA Unzips ◦DNA Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds 3 EASY STEPS

STEP 1: ◦DNA Unzips ◦DNA Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds 3 EASY STEPS

Replication Fork The areas where the double helix separates are called replication forks because of their Y shape. Once the 2 strands are separated, additional proteins attach to each strand, holding them apart. 18

STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides 5’ 3’ 3 EASY STEPS

5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

5’ 3’ STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides 3 EASY STEPS

5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

5’ 3’ 5’ 3’5’ 3’ 3 EASY STEPS STEP 2: ◦Complimentary Base Pairing ◦DNA Polymerase adds matching nucleotides

STEP 3: ◦DNA Ligase Rezips DNA 5’ 3’ 5’ 3’5’ 3’ 3 EASY STEPS

DNA REPLICATED! Two IDENTICAL copies of DNA; one copy goes into each new cell Blue – Original DNA Green – New DNA DNA replication is a semi-conservative process; there is not 1 new set and 1 old set. Each set of DNA contains 1 old strand and 1 new strand. 5’ 3’ 5’ 3’5’ 3’

Checking for Errors  Errors sometimes occur and the wrong nucleotide is added to the new strand.  An important feature of DNA replication is that DNA polymerases have a “proofreading” role.  It can backtrack to remove the incorrect nucleotide.  Reduces errors in DNA replication to about one error per 1 billion nucleotides. 33

G 1 : The cell grows – makes more cytoplasm & organelles; cell carries on normal metabolic activity (respiration, cell transport, etc). S: DNA is replicated. G 2 : The cell continues to grow, preparing for mitosis. Let’s recap Interphase…

Mitosis Once the cell is ready to begin dividing, it enters MITOSIS. The purpose of mitosis is to separate the two sets of DNA into TWO DIFFERENT NUCLEI – each having it’s own complete set of chromosomes. Cells are diploid (2n)

Mitosis Mitosis has four phases: Prophase Metaphase Anaphase Telophase

Cytokinesis Once two nuclei have been formed, the cell can divide its cytoplasm, which includes all its organelles, into two new daughter cells. This process is known as cytokinesis.

Mitosis occurs in Eukaryotes. Why? Because they have a nucleus! Binary Fission occurs in Prokaryotes. Asexual reproduction Cellular Division in Prokaryotes Cellular Division in Prokaryotes Fission

Checkpoints Checkpoints Fissin

Ignoring Checkpoints Ignoring Checkpoints n

Cancer