• If you were going to build something, what is the most important item that you would need? Explain why in at least 5 coherent sentences.

DNA, RNA, & PROTEIN SYNTHESIS

DNA DISCOVERY

DNA DISCOVERY

Frederick Griffith-British• Studied the cause of pneumonia and

possible vaccines.• Discovered two strains, S and R.• S-strain is live and causes disease. Named

for smooth sugar-coat colonies.• R-strain does not cause disease and has

rough colonies without a sugar-coat.

Griffith’s Experiment

Observation: Organisms are able to pass on their traits to their offspring according to the Laws of Genetics as developed by Gregor Mendel.

Question: What, within cells, serves as the genetic code material?

Griffith’s Experiment

Hypothesis: – By manipulating exposure to

different strains of bacteria, the specific chemical within cells that serves as the genetic material will be isolated.

Griffith’s Experiment

Procedure: • Griffith injected

some of the R-strain bacteria into mice. – What do you think

happened?

Griffith’s Experiment• Griffith injected

some of the S-strain bacteria into mice. – What do you

think happened?

Griffith’s Experiment• Griffith knew that

polysaccharides are not affected by heat, so he used heat to kill some of the S-strain bacteria and then injected them into mice.

• What do you think happened?

Griffith’s Experiment• Keep in mind that neither

dead S-strain nor live R-strain bacteria killed the mice.

• Griffith then mixed some of the heat-killed S-strain and some of the live R-strain bacteria and then injected them into mice.

• What do you think happened?

Griffith’s Experiment

Conclusion:• The polysaccharide coating is not the

genetic material. • When mixed, the R-strain bacteria

were able, somehow, to absorb genetic material from the dead S-strain and turn into S-strain bacteria.

• This ability was subsequently named transformation.

Griffith’s Experiment

Theory: A specific chemical controlled the transformation of cells.

DNA DISCOVERYOswald Avery-American• Expanded on Griffith’s experiments.Observation:

A specific chemical controls transformation.

Question: What chemicals are present in cells that can control transformation?

Hypothesis: Either protein, RNA, or DNA control cell transformation.

AVERY’S EXPERIMENT

Procedure• Using live S cells, Avery separately

destroyed the proteins, RNA, and then DNA.

• These separate batches were mixed with R cells again and injected into the mice.

AVERY’S EXPERIMENT

• R-cell with no-protein S cells= dead mice.

• R-cell with no-RNA S cells = dead mice.

• R-cell with no-DNA S cells= normal mice.

AVERY’S EXPERIMENT

Conclusion: Without DNA, the S cells could not transform the R cells. DNA must be the transforming agent.

DNA DISCOVERY

Hershey-Chase Experiment- Americans• Set out to determine if DNA or

proteins were hereditary material in viruses.

Observation: Previewed Griffith/Avery experiment results.

HERSHEY-CHASE EXPERIMENT

Question: What chemical allows a virus to infect a bacterium?

Hypothesis: If DNA and proteins are chemically labeled, then the hereditary chemical will show up in the reproduced cells.

HERSHEY-CHASE EXPERIMENT

Experiment:• Labeled virus proteins with radioactive

sulfur.• Labeled virus DNA with radioactive

phosphorus.• Allowed each sample to separately infect

E. coli.• Once viruses are removed from the

bacterium, the bacterial cells could be tested for each radioactive sample.

HERSHEY-CHASE EXPERIMENT

Conclusion: The DNA had completely transferred, while

trace amounts of protein were present in the new cells.

DNA…. -is the hereditary material in viruses.-Controls and determines the traits of an organism-Maintains control by producing proteins

Proteins control all body processes.

Discovery of DNA1. What makes the S strain bacteria

virulent?2. Why was Griffith’s Fourth experiment

so important?3. What did the Hershey-Chase

experiment prove?4. According to Avery, what is the role of

DNA during Griffith’s experiments?5. List the steps of the Scientific Method.

DNA STRUCTURE

DNA STRUCTURE

• Consists of repeating subunits called nucleotides

• Nucleotide parts are all held together with covalent bonds

• Nucleotides have 3 parts:– SUGAR– NITROGENOUS BASE– PHOSPHATE GROUP

DNA Nucleotide

DNA STRUCTURE• Sugar: Deoxyribose, a 5

carbon sugar• Phosphate Group: One

phosphorus atom with four oxygen atoms. – The phosphate attaches to

the deoxyribose at the methyl group.

– This forms the backbone of DNA.

DNA STRUCTURE

• Nitrogen Bases: – Adenine, Thymine, Guanine, and Cytosine

• Nitrogen bases are carbon rings with random nitrogen atoms– Purines= double-ringed bases, Adenine and

Guanine– Pyrimidines= single-ringed bases, Thymine

and Cytosine

DNA STRUCTURE

DNA STRUCTURE

DNA STRUCTURE• Nitrogen bases stick out to the inside,

toward each other. • Adenine always pairs with Thymine, and

Cytosine always pairs with Guanine.• The base pairs are held together with

weak hydrogen bonds.• The percentage of Adenine always equals

the percent of Thymine; Guanine percentage always equals Cytosine percentage.

Base PairingStars represent hydrogen bonds

DNA STRUCTURE

Two single strands of DNA are bound together, forming a double-helix

The strands are complementary to each other, not identical.

Watson and Crick first proposed this theory of a double helix.

DNA Structure1. Compare a purine to a pyrimidine.2. Why does Adenine bond with Thymine and

not with Cytosine?3. Weak hydrogen bonds hold the DNA helix

together. What is the importance of using weak bonds?

4. If 15% of the nucleotides in DNA are cytosine, what percentage of the nucleotides are adenine? Why?

5. What types of bonds exist in DNA and where do they work?

DNA Replication

DNA Replication

Chromosomes are long strands of DNA that must be duplicated before cell division.

Complementary strands of the double helix must separate before replication occurs.

Leading Strand

Lagging Strands

DNA Replication

These strands divide by breaking the weak hydrogen bonds between the nucleotides.

DNA Helicase is the enzyme that breaks the hydrogen bonds between the nitrogen bases.-The area where the helix splits is called the replication fork.

DNA Replication

DNA Replication

Free-floating nucleotides bind to the newly uncovered nucleotide sequences.

DNA Polymerase is an enzyme that adds the new nucleotides.

DNA Polymerase works in opposite directions on the separated DNA strand.

DNA Replication

The double helix unzips entirely and forms two identical double helix.

These two helices are each made of one original strand and one new strand. (Semi-Conservative Replication)

Replication1. What makes DNA replication semi-

conservative?2. Compare DNA Helicase to DNA

Polymerase.3. How do the DNA polymerases

travel on the DNA strands?4. How is eukaryotic DNA replicated

so quickly?5. Compare the Leading and Lagging

Strands.

1 2

3

4

Protein Synthesis

Protein Synthesis

Directions of DNADNA follows a specific path to produce

proteins.

RNA is used as an intermediate to proteins.

DNA > Transcription > RNA > Translation > Protein

Protein SynthesisRNA vs. DNA

RNA has one strand… DNA has two strands

RNA uses Ribose sugar….DNA uses Deoxyribose.

Uracil replaces Thymine in RNARNA strands are very short, and DNA strands are very long.

RNA with Guanine

RNA with Adenine

RNA with Cytosine

RNA with Uracil

Protein Synthesis

Types of RNAmRNA- Messenger RNA takes the directions of DNA to the rRNA.

rRNA- Ribosomal RNA uses the DNA code to produce proteins.

tRNA- Transfer RNA brings amino acids together to produce proteins.

Types of RNA

TRANSCRIPTIONJohn Kyrk Transcription Transcription Animation

Simple Animation

TRANSCRIPTION

RNA Polymerase binds to a DNA promoter region, which is a specific DNA sequence.

– This causes DNA strands to relax and unwind in one section.

TRANSCRIPTIONRNA Polymerase adds free RNA nucleotides

to begin producing an RNA strand.

– This RNA strand is COMPLEMENTARY to the DNA strand.

– Once the RNA Polymerase has finished, the DNA retwists.

TRANSCRIPTIONA Termination Signal stops the RNA

Polymerase. – This signal is another specific DNA

sequence.– Both DNA and RNA strands are released.– The new RNA strand can be rRNA, mRNA, or

tRNA.– RNA strands are then manipulated in

Translation to make proteins.

Pre-mRNA Editing1. 5’ Cap-

2. 3’ Tail-

3. Introns vs Exons

Transcription Practice

• DNA: AATCGA• RNA:

• DNA: ATACGGACA• RNA:

• DNA: TACGATCGCCGA• RNA:

The Genetic Code

Translation Animation

The Genetic Code

A set of rules that govern how nucleotide sequence correlates to a specific amino acid.

Following Transcription, the mRNA strand is “read” in units of three adjacent nucleotides called a Codon.

The Genetic Code

CODONS are 3-nucleotide sequences on mRNA that code for specific amino acids or a start/stop signal.

Several codons may code for the same amino acid, but each codon codes for only one amino acid.

The Genetic Code

AUG is the universal START codon, while UGA, UAA, and UAG are all STOP codons.

Translation starts with start codons and ends with stop codons.

TRANSLATION

Animation

TRANSLATION

A ribosome attaches to a strand of mRNA, allowing a tRNA anti-codon molecule to attach to the correct mRNA codon.

The ribosome moves down the mRNA from 5’ to 3’.

TRANSLATION

While the first tRNA molecule is attached to the mRNA, the ribosome moves down the sequence of nucleotides.

When the ribosome moves, it allows the next tRNA molecule to attach to the next codon.

TRANSLATION

When two consecutive tRNA molecules are attached to the mRNA, peptide bonds form between the carried amino acids.

Both remain attached to the second tRNA molecule.

TRANSLATION

These steps continue producing a long strand of amino acids until the ribosome reaches a stop codon. This releases the new polypeptide.

Translation components break apart and the newly created protein is sent to its final destination.

Protein Synthesis1. Contrast Codons and Anti-codons.

2. Compare Translation to Transcription.

3. What does the Genetic Code do?

4. What are the roles of each type of RNA?

5. How does a tRNA anti-codon sequence compare to the original DNA sequence?

LINKS TO ANIMATIONS • http://www.bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.sw

f

• http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf

• http://www.johnkyrk.com/DNAreplication.html

• http://learn.genetics.utah.edu/content/begin/dna/transcribe/

• http://www.johnkyrk.com/DNAtranscription.html

• http://www.biostudio.com/demo_freeman_protein_synthesis.htm

• http://www.johnkyrk.com/DNAtranslation.html

CREDITS• Outline information adapted from http://biology.clc.uc.edu/courses/bio104/dna.htm• http://porpax.bio.miami.edu/~cmallery/150/gene/sf11x1a.jpg• http://www.offresonance.com/wp-content/uploads/2008/05/450px-griffith_experimentsvg.png• https://filebox.vt.edu/users/mahogan2/Filebox%20Portfolio/Webquest%20for%20DNA_files/image004.jpg• https://www.msu.edu/course/isb/202/ebertmay/drivers/nucleotide.jpg• http://coris.noaa.gov/glossary/nucleotide_186.jpg• http://www.dnahandbook.com/s/10009/Images/purines.gif• http://www.brooksdesign-cg.com/Images/cg/SCdna6.gif• http://www.mariemontschools.org/halsall/images/dna_molecule.gif• http://porpax.bio.miami.edu/~cmallery/150/gene/c7.16.14.fork.jpg• http://www.elmhurst.edu/~chm/vchembook/images/582dnarepline.gif• http://courses.cm.utexas.edu/jrobertus/ch339k/overheads-2/ch10_DNA-rep.jpg• http://www.biologycorner.com/resources/replication.gif• http://library.thinkquest.org/18617/media/replication-simple.gif• http://upload.wikimedia.org/wikipedia/commons/2/2c/RNA_chemical_structure.GIF• http://porpax.bio.miami.edu/~cmallery/150/gene/c7.17.7b.transcription.jpg• http://stardec.ascc.neu.edu/~bba/CBIO3580/DOGMA/Fig13_18.JPG• https://www.msu.edu/course/lbs/333/fall/images/geneticcode.gif• http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Translation.gif• http://www.biologycorner.com/resources/translation_lettered.jpg