Do Now!! (period 2 & 6)  What does DNA stand for?  What is the shape of DNA in eukaryotic cells? In prokaryotic?  How is DNA considered a “blueprint”?

Objectives  To define DNA and understand its significance  To summarize the experiments of Griffith and Avery leading to discovery of DNA as genetic material  To introduce viruses and their characteristics

Ch. 12: Molecular Genetics!!

Activity!  With your group members, please answer the questions about DNA in the table.  We will come together as a class to complete the table!

DNA  DNA: Deoxyribonucleic acid  Located in the nucleus of cells:  If red blood cells don’t have a nucleus, how can we test blood for DNA?  The function of DNA is to tell the cells how to produce things that make you up (Blueprint):  How to make proteins!

When was DNA discovered, and who discovered such a glorious thing?  Scientists tried to determine the source of genetic information:  Nucleic acid (DNA) or proteins??

Do Now!! (period 6)  Is bacteria living or non-living?  What shape does bacterial DNA have?  What do we mean by “strains” of bacteria?

Objectives  To define DNA and understand its significance  To summarize the experiments of Griffith and Avery leading to discovery of DNA as genetic material  To extract DNA from strawberries

1928 Frederick Griffith:  First major experiment that led to discovery of DNA  Studied two strains of the bacteria Streptococcus pneumoniae (causes pneumonia):  Rough strain (R) and Smooth strain (S)  S strain has protective outer coating, R strain does not  S strain causes pneumonia and the R strain does not

What do you think happened??

1928 Frederick Griffith:  Discovered that the heat killed S type bacteria was turning the R type bacteria into smooth!!  Called it the transforming factor  Set up stage for search to find this transforming substance

1944 Oswald Avery:  Purified protein, RNA, and DNA separately from Streptococcus pneumonia bacteria to determine which would transform the harmless bacteria.  Protease  destroys proteins  mice died  RNase  destroys RNA  mice died  DNase  destroys DNA  mice survived  Conclusion: DNA is the genetic material!!

Nobody believed Avery  His conclusions were not widely accepted in scientific community.  Other scientists tried to determine what this transforming factor was!  Is it protein or DNA?  Lets ask Hershey and Chase!

Do Now!!  Which strain of bacteria killed the mice in Griffith’s experiment?  What happened to the R strain that caused death in the mice? What is that called?  What conclusion did Avery reach?

Objectives  To identify the 6 characteristics of viruses  To define and label a bacteriophage  To determine the 5 stages of viral attack!

Hershey and Chase  Worked with viruses to determine what the “transforming factor” was.  What is a virus, and how does it work?? Martha Chase and Alfred Hershey T4 bacteriophage

6 Characteristics of Viruses  1. Have their own genome (genetic make up) made of either DNA or RNA  2. Do not have enzymes, ribosomes, or ATP  3. Have external protein shells (capsids) T4 bacteriophage HIV Rhinovirus

6 Characteristics of Viruses  4. Infect only specific cells  5. 2 life cycles (lytic and lysogenic)  Lytic – breaks out and spreads (destroys the cell)  Lysogenic- hangs around (does not destroy cell)  6. Smaller than bacteria Ebola Virus Influenza Measles

Do Now!! (period 2)  What are the 6 characteristics of a virus?  What is the difference between lysogenic and lytic life cycles of a virus?

Objectives  To define and label a bacteriophage  To identify the 5 stages of viral attack

How a virus attacks!  hQ hQ

Bacteriophage: a virus that attacks bacteria Capsid head DNA Tail sheath Tail fibers Protein coat

Lytic and Lysogenic cycles:

Do Now!! (period 2 & 6) Please label the structure below

Objectives  To identify the 5 stages of viral attack  To discuss the importance of Hershey and Chase’s experiment

5 Stages of Attack! 1) Attachment: virus attaches to its host 2) Injection: virus injects its DNA into the host cell. 3) Replication: virus copies its genetic material many times. 4) Assembly: virus assembles more viruses 5) Release: Viruses are released from the cell, ready to attach to new cells!

Bacteriophage attack  mDI mDI

Worksheet!

Do Now!!  What are the 5 stages of attack for a virus?  Label the pictures below with the 5 stages!

Objectives  To discuss the importance of Hershey and Chase’s experiment  To identify the importance of radioactive labeling

1952 Hershey and Chase  Radioactive Labeling:  Replacing atoms with radioactive isotopes  Radioactivity acts as a label  Make note!  Proteins contain sulfur (in certain amino acids)  DNA contains phosphorus (in backbone) Methionine Cysteine Sulfur

Phosphate

Hershey and Chase  Radioactive Labeling:  Used radioactive phosphorus ( 32 P) to identify DNA in the bacteriophages  Used radioactive sulfur ( 35 S) to identify proteins in the bacteriophages  Radioactive bacteriophages infected bacteria cells  Used radioactivity to identify movement of proteins and DNA

1952 Hershey and Chase  They found radioactive sulfur outside of bacteria cells and radioactive phosphorus inside bacteria cells  Only radioactively labeled DNA was inside of the bacteria cell  Therefore, DNA is genetic material!!

Do Now!!  Take out your scientists packets and fill out the section on Hershey and Chase!

Objectives  To identify the structure of DNA  To label a molecule of DNA  To define chromosomes and their structure

Now we know DNA carries genetic material! Soooo now what?  Phoebus Levene discovered that DNA is made of nucleotides  DNA is a nucleic acid…  So what are nucleotides?

DNA Structure  Nucleotides:  5 carbon sugar (Deoxyribose)  Phosphate Group  Nitrogen base

Nitrogenous Bases  Purines  Have 2 rings (double ring structure): a. Adenine (A) b. Guanine (G)  Pyrimidines  Have 1 ring (single ring structure): a. Thymine (T) b. Cytosine (C) c. Uracil (U) instead of Thymine in RNA

DNA Structure

Chargaff’s Rule  Erwin Chargaff  Discovered that A pairs with T and C pairs with G.  Chargaff’s rule:  A=T, C=G  Amounts vary between species

Draw in the complimentary sequence A T G C T A A T T C A T G A A C

Do Now!!  What makes up a nucleotide?  What is the difference between purines and pyrimidines? List them!  Compliment the following sequence: A T G C A A A T G C G A C C

Objectives  To discuss Rosalind Franklin’s contribution to discovering the structure of DNA  To identify the accomplishments of Watson and Crick  To define a chromosome and label its important parts

Rosalind Franklin  Used X-ray diffraction to determine shape of DNA  X-ray diffraction:  X-rays aimed at molecules, bounce off electrons  Determines the molecule’s shape

Rosalind Franklin  Took now famous photo 51  Data indicated that DNA was a double helix shape  Helped Watson and Crick solve the structure of DNA

Watson and Crick  Built a model of the double helix DNA molecule:  two outside strands consist of alternating sugar and phosphate molecules  thymine and adenine bases pair to each other by two hydrogen bonds  cytosine and guanine bases pair to each other by three hydrogen bonds

DNA Structure  DNA looks like a twisted ladder  Rails: alternating deoxyribose sugars and phosphates  Rungs (steps): base pairs (C-G, A-T) bonded by hydrogen bonds

Label the parts of the DNA molecule

Orientation of DNA- Anti Parallel o On the top rail, the strand is said to be oriented 5′ to 3′. o The strand on the bottom runs in the opposite direction and is oriented 3′ to 5′. o 5′: exposed phosphate group o 3′: exposed hydroxyl group (-OH)

Chromosome Structure  DNA coils around histones (proteins) to form nucleosomes  This coils to form chromatin fibers  The chromatin fibers supercoil to form chromosomes that are visible in the metaphase stage of mitosis.