WARM UP Mon 1010 Tues 1011 What happens

WARM UP Mon. (10/10) / Tues. (10/11) What happens during the S phase of the cell cycle? a. b. c. d. The cell grows The DNA replicates The cell splits in half The cell is in its resting stage HINT: DNA S-phase Synthesis happens during Answer: B Turn In: Homework: Study for DNA Vocab Quiz Exam: DNA Vocab Quiz

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The Cell Cycle

The Cell Cycle The cell cycle is a series of events that cells go through as they grow and divide.

Cell Cycle Stages The cell cycle is made up of two main stages: 1. Interphase: Includes G 0, G 1, S and G 2 phase. Cells spend most of their time in interphase between cell division. 1. Cell Division: Includes M Phase which consists of Mitosis and Cytokinesis (when the cell splits in half)

During the cell cycle, the following happens: G 1 Phase: Cell grows & organelles replicate S Phase: DNA is replicated G 2 Phase: Cell prepares for division M Phase: Cell divides to form 2 daughter cells. G 0 Phase: Resting phase http: //www. youtube. com/watch? v=lf 9 rcqifx 34

G 1 Phase Also called Gap 1 During this phase, everything in the cell, except DNA, replicates The cell grows bigger to hold all the new cell parts The larger cell will now enter S Phase

G 2 Phase After replicating DNA in the S Phase, cells will move to G 2 (also called Gap 2) During this phase the cell continues to grow and then prepares for cell division in the M phase

G 0 Phase After cell division, certain cells will not enter back into the cell cycle (ex: brain cells (neurons) and heart muscle cells) G 0 is a resting state where cells continue to carry out normal cellular process, but do not need to grow and divide

G 0 Phase If cells need to start dividing again, it is possible for them to reenter the cell cycle at the G 1 Phase

Checkpoints There are 3 checkpoints throughout the cell cycle that “check” to make sure the cell is ready to enter the next phase If the checkpoints find a mistake, the cell cycle will stop for that cell

Checkpoints If the checkpoints do not work properly, cells can continue in the cell cycle and problems such as cancer might occur http: //www. youtube. com/watch? v=2 a. Vn. N 4 Re. Py. I – Watch 4: 25 -6: 27

How long does the cell cycle take? …each cell is different! Type of Cell New cells made every… White Blood Cells 10 hrs - lifetime Sperm Cells 2 -3 Days Digestive Tract Cells 2 Days – 1 week Skin Cells 2 -3 Weeks Red Blood Cells 3 -4 Months Pancreas Cells 1 Year or More Bone Cells 25 -30 Years Neurons (Brain Cells) 50 Years - lifetime Heart Muscle Cells 50 Years - lifetime

There’s more! We will review the S Phase & M Phase of the cell cycle in more detail later

DNA http: //www. youtube. com/watch? v=zwibg. NGe 4 a. Y Watch until 2: 45 http: //www. brainpop. com/science/cellularlifeandgenetics/dna/

Sum it Up Question: • How does DNA relate to proteins?

DNA is short for Deoxyribonucleic acid • It is located in the nucleus of cells in eukaryotes and the cytoplasm of prokaryotes. • It is the Blueprint that makes you who you are. • The shape of DNA is a double helix.

STRUCTURE OF DNA The subunit (monomer) of DNA is a nucleotide. Nucleotides have 3 parts 1. 2. 3. The a phosphate group , a sugar (deoxyribose), a nitrogenous base. sugar and Phosphate are the same in every nucleotide, but the base differs.

Four bases 1. 2. 3. 4. Adenine: Guanine: Cytosine: Thymine: A G C T Adenine (A) will always pair up with Thymine (T) and Cytosine (C) will always pair up with Guanine (G)

Bases There are two categories of bases, with 2 bases in each category.

Unnumbered Figure (page 292) Purine and pyridimine Purine = Double carbon ring: Guanine and Adenine Pyrimidine = Single Carbon ring: Cytosine and Thymine

Figure 16. 6 Base pairing in DNA Hydrogen bonds hold the bases together 2 Hydrogen bonds between A and T 3 Hydrogen bonds between G and C

Figure 16. 5 The double helix The rungs of the Helix are made up of the nitrogenous bases The Two strands run anti-parallel to each other

Figure 16. 3 The structure of a DNA strand The backbone of the Helix is made up of Sugar and Phosphates http: //www. youtube. com/watch? v=qy 8 dk 5 i. S 1 f 0

Scientists: 1) Hershey and Chase: confirmed that DNA is the genetic material. They did an experiment where they used viruses with radioactive labels to infect bacteria.

2) Rosalind Franklin: studied DNA by using x-ray diffraction. She discovered that DNA looks like coiled spring. This spring shape is called a helix.

3) Erwin Chargaff: Erwin Chargaff discovered that in DNA the # of A’s always equaled the # of T’s and also the #of G’s always equaled the # of C’s. Known as Chargaff’s Rule Clip: http: //www. youtube. com/watch? v=Hv. Jlnujm. Ycg

4) Watson and Crick: built a model of DNA. They found out that DNA is a double helix; a spiral staircase with two strands of nucleotides whose bases face each other. It is held together by hydrogen bonds. T forms a bond with A and C with G. http: //www. hhmi. org/biointeractive/wat son-constructing-base-pair-models

DNA Replication

Back to the Cell Cylce

Synthesis Phase (S Phase) – commonly called DNA Replication DNA must be copied so that when the cell divides, the 2 new cells each have DNA. This process of copying DNA is called replication. Clip: http: //www. youtube. com/watc h? v=s 5 Kbv. U 2 Gz. ZY

Replication Step 1 Helicase (an enzyme) will break the Hydrogen bonds holding the bases together

Replication Step 2 DNA polymerase: (an enzyme) brings in the matching bases to make the complementary strand

Complementary Strands The two strands are complementary of each other. Which means the base pairs are together A=T and C=G. So the order of bases on the original strand determines the order of bases on the new strand being attached. Song links: http: //www. youtube. com/watch? v=sst. JI 3 ag. Bc. M http: //www. youtube. com/watch? v=hy. I 2 m. Yfbbxk

DNA Repair DNA Polymerase – not only puts bases in order, but it also proofreads what it has laid down. If the base is wrong, polymerase will undo it by going back and removing the wrong base.

Replication Step 3: When all base pairs have been matched, Ligase: (an enzyme) sticks the bases together using Hydrogen bonds and seals the ends of the DNA strands.

Replication Step 4: Gyrase: (an enzyme) Winds the DNA molecules back into a double helix

The result of replication is two identical copies of the original DNA strand. It is called semi-conservative because half of the strand is new and the other half is the original strand.

http: //www. youtube. com/watch? v=zd. Dki. Rw 1 Pd. U

Each strand has a 5’ end a 3’ end. Because they line up opposite of one another they are called anti-parallel

Replication starts at the 5’ end and works towards the 3’ end.