Welcome 1/11/15 – 1/15/15 Warm up #6-10 Vocab #12 Turn in Cornell Notes Notes on the history of DNA, Components of DNA Check for understanding questions Assign DNA Project Homefun: None so that you can work on DNA project immediately! copyright cmassengale1

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History of DNA Early scientists thought protein was the cell’s hereditary material because it was more complex than DNA Proteins were composed of 20 different amino acids in long polypeptide chains copyright cmassengale3

Transformation Fred Griffith worked with virulent S and nonvirulent R strain Pneumoccocus bacteria He found that R strain could become virulent when it took in DNA from heat-killed S strain Study suggested that DNA was probably the genetic material copyright cmassengale4

Griffith’s Experiments S strain: causes disease R strain: harmless S strain: heat killed Mixture: R, dead S Mouse dies of pneumonia. Mouse dies of pneumonia. Mouse lives. Mouse lives. Live S strain

Griffith Experiment copyright cmassengale6

History of DNA Chromosomes are made of both DNA and protein Experiments on bacteriophage viruses by Hershey & Chase proved that DNA was the cell’s genetic material copyright cmassengale7 Radioactive 32 P was injected into bacteria!

Bacterial Viruses Bacteriophage: a kind of virus that infects bacteria tail fiber DNA head tail sheath

Hershey-Chase Experiment Bacteriophage with radioactive tag in protein coat Bacteriophage with radioactive tag in DNA Phage infects bacterium. Phage infects bacterium. Radioactivity inside bacterium No radioactivity inside bacterium

Discovery of DNA Structure Erwin Chargaff showed the amounts of the four bases on DNA ( A,T,C,G) In a body or somatic cell: A = 30.3% T = 30.3% G = 19.5% C = 19.9% copyright cmassengale10

Chargaff’s Rule [A] = [T] and [C] = [G]

Chargaff’s Rule Adenine Thymine Adenine must pair with Thymine GuanineCytosine Guanine must pair with Cytosine The bases form weak hydrogen bonds copyright cmassengale12 G C TA

DNA Structure Rosalind Franklin took diffraction x-ray photographs of DNA crystals In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays copyright cmassengale13

Franklin’s X-rays DNA is a helix. Likely two strands to the molecule Nitrogenous bases near the center of the molecule

The Work of Watson and Crick DNA is a double helix, in which two strands of nucleotide sequences are wound around each other.

The Double Helix: Antiparallel Strands The two strands in a DNA molecule run in opposite directions.

Check for understanding 1. Before, why did scientists thought protein was the cell’s hereditary material? 2. Name the scientists and their experiments that rejected the notion that protein was the cell’s hereditary material. And what is indeed the cell’s hereditary materials? 3. What is Chargaff’s rule? 4. How did DNA model first constructed?

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The Role of DNA: Storing Information The genetic material stores information needed by every living cell.

The Role of DNA: Copying and Transmitting Copying Information Transmitting Information

The Role of DNA: Summary 1. Store information 2. Copy information for daughter cells 3. Transmit information to daughter cells

DNA DNA. DNA is often called the blueprint of life. In simple terms, DNA contains the instructions for making proteins within the cell. 22

DNA Why do we study DNA? We study DNA for many reasons, e.g., its central importance to all life on Earth, medical benefits such as cures for diseases, better food crops. 23

Chromosomes and DNA Our genes are on our chromosomes. Chromosomes are made up of a chemical called DNA. 24

The Shape of the Molecule DNA is a very long polymer. The basic shape is like a twisted ladder or zipper. This is called a double helix. 25

The Double Helix Molecule The DNA double helix has two strands twisted together. 26

One Strand of DNA The backbone of the molecule is alternating phosphates and deoxyribose sugar The teeth are nitrogenous bases. 27 phosphate deoxyribose bases

One deoxyribose together with its phosphate and base make a nucleotide. 28 CC C O Phosphate O C C O -P O O O O O O O Nitrogenous base Deoxyribose

One Strand of DNA One strand of DNA is a polymer of nucleotides. One strand of DNA has many millions of nucleotides. 29 nucleotide

Four nitrogenous bases Cytosine C Thymine T Adenine A Guanine G 30 DNA has four different bases:

Two Kinds of Bases in DNA Pyrimidines are single ring bases. Pyrimidines are single ring bases. Purines are double ring bases. Purines are double ring bases. 31 C C C C N N O N C C C C N N N N N C

Thymine and Cytosine are pyrimidines Thymine and cytosine each have one ring of carbon and nitrogen atoms. Thymine and cytosine each have one ring of carbon and nitrogen atoms. 32 C C C C N N O N cytosine C C C C N N O O thymine C

Adenine and Guanine are purines Adenine and guanine each have two rings of carbon and nitrogen atoms. Adenine and guanine each have two rings of carbon and nitrogen atoms. 33 C C C C N N N Adenine N N C C C C C N N O N Guanine N N C

Antiparallel Strands One strand of DNA goes from 5’ to 3’ (sugars) The other strand is opposite in direction going 3’ to 5’ (sugars) copyright cmassengale34

Two Stranded DNA Remember, DNA has two strands that fit together something like a zipper. Most DNA has a right- hand twist with 10 base pairs in a complete turn Most DNA has a right- hand twist with 10 base pairs in a complete turn The teeth are the nitrogenous bases but why do they stick together? 35

Hydrogen Bonds The bases attract each other because of hydrogen bonds. Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. The bonds between cytosine and guanine are shown here with dotted lines 36 C C C C N N O N C C C C N N O N N N C

Hydrogen Bonds, Hydrogen Bonds, cont. When making hydrogen bonds, cytosine always pairs up with guanine Adenine always pairs up with thymine 37 C C C C N N N N N C C C C C N N O O C

DNA by the Numbers Each cell has about 2 m of DNA. The average human has 75 trillion cells. The average human has enough DNA to go from the earth to the sun more than 400 times. DNA has a diameter of only m. 38 The earth is 150 billion m or 93 million miles from the sun.

Draw a model of DNA double helix with all of its components label

How the Code Works The combination of A,T,G,C determines what traits you might have..... C A T C A T = purple hair T A C T A C = yellow hair

Think of the bases of DNA like letters. Letters form words.... Words form sentences.... *endless combinations

Let's Review What We Know About DNA 1. DNA stands for: De _____ ribo ______ acid 2. What is the shape of DNA? _______________ 3. Who established the structure of DNA? ____________ 4. Adenine always pairs with _______________ 5. The sides of the DNA ladder are deoxyribose and _____ 6. Guanine always pairs with _____________ 7. What is the complimentary sequence: A A T G C A 8. The two sides of DNA are held together by _______ bonds. 9. DNA is composed of repeating subunits called ______________________ 10. What are the 4 bases that make up the rungs of the DNA ladder? _______________________________________

copyright cmassengale44

Replication Facts DNA has to be copied before a cell divides DNA has to be copied before a cell divides DNA is copied during the S or synthesis phase of interphase DNA is copied during the S or synthesis phase of interphase New cells will need identical DNA strands New cells will need identical DNA strands copyright cmassengale45

Synthesis Phase (S phase) S phase during interphase of the cell cycle Nucleus of eukaryotes copyright cmassengale46 Mitosis -prophase -metaphase -anaphase -telophase G1G1 G2G2 S phase interphase DNA replication takes place in the S phase.

DNA REPLICATION the process by which DNA makes a copy of itself (cell division) SEMI-CONSERVATIVE - half of the old strand is saved

Synthesis of the New DNA Strands The Lagging Strand is discontinuously The Lagging Strand is synthesized discontinuously against overall direction of replication This strand is made in MANY short segments It is replicated from the replication fork toward the origin copyright cmassengale48 RNA Primer Leading Strand DNA Polymerase 5’5’ 5’ 3’ Lagging Strand 5’ 3’

Lagging Strand Segments Okazaki Fragments - lagging strand Okazaki Fragments - series of short segments on the lagging strand Must be joined together by an enzyme Must be joined together by an enzyme copyright cmassengale49 Lagging Strand RNAPrimerDNAPolymerase 3’ 5’ Okazaki Fragment

Joining of Okazaki Fragments The enzyme Ligase joins the Okazaki fragments together to make one strand The enzyme Ligase joins the Okazaki fragments together to make one strand copyright cmassengale50 Lagging Strand Okazaki Fragment 2 DNA ligase DNA ligase Okazaki Fragment 1 5’ 3’

Replication of Strands copyright cmassengale51 Replication Fork Point of Origin

Base Pair Rule One side: A T A T C A T G C G G G Other side:

Proofreading New DNA DNA polymerase initially makes about 1 in 10,000 base pairing errors DNA polymerase initially makes about 1 in 10,000 base pairing errors Enzymes proofread and correct these mistakes Enzymes proofread and correct these mistakes The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors copyright cmassengale53

Semiconservative Model of Replication Idea presented by Watson & Crick Idea presented by Watson & Crick The The two strands of the parental molecule separate, and each acts as a template for a new complementary strand New DNA consists of 1 PARENTAL (original) and 1 NEW strand of DNA copyright cmassengale54 Parental DNA DNA Template New DNA

DNA Damage & Repair Chemicals & ultraviolet radiation damage the DNA in our body cells Cells must continuously repair DAMAGED DNA Excision repair occurs when any of over 50 repair enzymes remove damaged parts of DNA DNA polymerase and DNA ligase replace and bond the new nucleotides together copyright cmassengale55

Question: What would be the complementary DNA strand for the following DNA sequence? DNA 5’-CGTATG-3’ copyright cmassengale56

Answer: DNA 5’-CGTATG-3’ DNA 3’-GCATAC-5’ copyright cmassengale57

RNA - the messenger *single strand *ribose sugar *contains no thymine, uracil instead

RNA carries the "message" to the ribosomes, where proteins are made

Transcription - process where RNA is made from DNA Translation - process where proteins are made from RNA

DNA --> RNA --> Protein Proteins are the building blocks of the organism (traits)

Transcription: DNA to RNA DNA: A T A G C G RNA:

copyright cmassengale65 1.Compare DNA vs. RNA 2.What is transcription? 3.Make up a sequence of DNA strand of 10 base pairs, then use it to make an RNA strand 4.What is translation?