CH 10

DNA, R

NA, AND PR

OTEIN SYN

THESIS

REVIEW What did Mendel tell us about

heredity?Did he know what was being

transmitted?

This chapter will help us identify the structure, and function of DNA.

10-1 DISCOVERY OF DNA10-2 STRUCTURE OF DNAYEAR SCIENTIST Conclusion

1928 Frederick Griffith

1940’s Oswald Avery

1952 Hershey & Chase

1953 Watson & Crick

early1950s

Rosalind Franklin

1949 Erwin Chargaff

SKIP 2-3 lines between

rows.

GRIFFITH’S EXPERIMENT• 1928 Britain• Studied Streptococcus

pneumoniae • Trying to develop a vaccine• Identified two strains1. virulent: disease causing

Colonies with smooth edges (S strain)2. non-virulent

Colonies with Rough edges (R strain)

10-1 DISCOVERY OF DNA10-2 STRUCTURE OF DNASCIENTIST ConclusionFrederick Griffith Virulent bacteria released ‘hereditary

factor’ that transformed the non-virulent bacteriaTransformation: movement of genetic material from one organism to another

Oswald Avery

Hershey & Chase

Watson & Crick

Rosalind Franklin

Erwin Chargaff

DNA

“Heredity factors” = genes

Genes are located on DNA molecule

AVERY’S EXPERIMENTSIs transforming agent protein, RNA, or DNA???• Used R and S strains on mice again.

10-1 DISCOVERY OF DNA10-2 STRUCTURE OF DNASCIENTIST ConclusionFrederick Griffith Virulent bacteria released ‘heredity

factor’ that transformed the non-virulent bacteriaTransformation: movement of genetic material from one organism to another

Oswald Avery DNA is responsible for transformation in bacteria.

Hershey & Chase

Watson & Crick

Rosalind Franklin

Erwin Chargaff

HERSHEY-CHASE EXPERIMENTBacteriophage: virus that infects bacteria

Is DNA or protein the hereditary material viruses transfer when they infect a bacterial cell?

All viral DNA entered bacterial cell.

Very little protein entered.

10-1 DISCOVERY OF DNA10-2 STRUCTURE OF DNASCIENTIST ConclusionFrederick Griffith Virulent bacteria released ‘heredity

factor’ that transformed the non-virulent bacteriaTransformation: movement of genetic material from one organism to another

Oswald Avery DNA is responsible for transformation in bacteria.

Hershey & Chase DNA is the hereditary molecule in viruses, not protein.

Watson & Crick

Rosalind Franklin

Erwin Chargaff

10-2 DNA STRUCTURE

• 1953• Watson and Crick

identified the 3-D structure of DNA

•Rosalind FranklinFemale scientistCrucial final clueX-Ray diffraction technique

10-1 DISCOVERY OF DNA10-2 STRUCTURE OF DNASCIENTIST ConclusionFrederick Griffith Virulent bacteria released ‘heredity

factor’ that transformed the non-virulent bacteriaTransformation: movement of genetic material from one organism to another

Oswald Avery DNA is responsible for transformation in bacteria.

Hershey & Chase DNA is the hereditary molecule in viruses, not protein.

Watson & Crick DNA’s structure is a “double helix” (2 strands of nucleotides twisted in a

spiral shape)Rosalind Franklin Shape of DNA

Erwin Chargaff

DNA made of 2 chains that wrap around each other to form a double helix

DNA NUCLEOTIDES• MONOMER of

nucleic acids• Three components

5-Carbon sugarPhosphate groupNitrogenous base

DNA DOUBLE HELIX• 2 strands of DNA likened to a twisted

ladder• Nitrogenous bases = “rungs”• Held together with H-Bonds between

complementary nitrogenous bases• Sugar and phosphate compose

“backbone” or “handrails”

NITROGENOUS BASES

Only 41. Adenine (A)2. Guanine (G)

3. Thymine (T)4. Cytosine (C)

Double ringed: Purines

Single ringed: Pyrimidines

COMPLEMENTARY BASES• 1949; Erwin Chargaff• %A = %T• %G = %C• ADENINE always bonds with THYMINE• GUANINE always bonds with CYTOSINE• Nitrogenous bases are complementary to

each other• What is the complementary strand to ATTG?

10-1 DISCOVERY OF DNA10-2 STRUCTURE OF DNASCIENTIST ConclusionFrederick Griffith Virulent bacteria released ‘heredity

factor’ that transformed the non-virulent bacteriaTransformation: movement of genetic material from one organism to another

Oswald Avery DNA is responsible for transformation in bacteria.

Hershey & Chase DNA is the hereditary molecule in viruses, not protein.

Watson & Crick DNA’s structure is a “double helix” (2 strands of nucleotides twisted in a spiral shape)

Rosalind Franklin Shape of DNA

Erwin Chargaff Base-pairing ruleA – TC - G

What is the complementary strand to A C C T G T G A G A C

G?

QUIZ NEXT CLASSMATCH THE FOLLOWING SCIENTISTS TO THEIR WORK• Frederick Griffith• Hershey & Chase• Watson & Crick• Erwin ChargaffStructure of a NUCLEOTIDEStructure of DNA• Purines vs. pyrimidines• Complelementary bases

10-3 DNA REPLICATION

• Process by which DNA is copied

• In nucleus• During s phase of cell

cycle prior to mitosis• Two strands of DNA

separate• Each strand serves as

a template(?) for new strand

STEPS 1. DNA unwound by helicase

Helicase moves along DNA & breaks H-bonds b/w bases

STEPS continued…Nucleotides floating in nucleus

DNA Polymerase adds complementary nucleotides to original strand

Covalent bonds b/w sugar and phosphates of adjoining nucleotides

Hydrogen bonds b/w bases

STEPSDNA Polymerase finishes and releases DNA strands• 2 identical DNA strands result

DNA REPLICATIONhttp://www.youtube.com/watch?v=yqESR7E4b_8

DNA REPLICATION REVIEWATC GTC GAT GTA AGG

1. Identify the complementary bases first2. Divide the two strands using one color3. Using a second color, identify the new

complimentary strand

ERRORS IN REPLICATIONNormally very accurateOne error per 1 billion nucleotidesDNA polymerase can proofread DNA for

mistakesWhen found, mistake is correctedMutation: change in nucleotide sequence

of a DNA molecule

CANCERMutation in genes that control cell division can result in

uncontrolled cell growth (cancer)Tumor: abnormal mass of cells

PROTEIN SYNTHESISFlow of genetic information:Genes in DNA are TRANSCRIBED into mRNA in the nucleusmRNA is TRANSLATED in cytoplasm into a sequence of amino

acids (protein)DNA RNA protein

transcription

translation

RNADNA = DEOXYribonucleic acidRNA = ribonucleic acidDifferences (3)1. Sugar: RNA = ribose DNA = deoxyribose2. Shape: RNA = single stranded DNA = double stranded3. Nitrogenous bases In RNA, replace thymine with Uracil (U)

TYPES OF RNA1. Messenger RNA (mRNA) Single stranded Carries instructions from a gene (DNA) to make protein to ribosome2. Ribosomal RNA (rRNA) Composes ribosome3. Transfer RNA (tRNA) Transfers amino acids to ribosome

TRANSCRIPTION Process by which genetic instructions in a specific gene are re-

written into mRNAIn nucleus1. RNA polymerase binds to promoter Enzyme forms RNA on a DNA templatePromoter: specific sequence of nucleotides that initiates

transcription

TRANSCRIPTION 2. RNA polymerase adds free RNA nucleotides that are complementary to template strand of DNA- Remember: in RNA, replace thymine with uracilDNA strand: ATCGACmRNA strand: UAGCUGDNA ATCGGATTACAmRNA UAGCCUAAUGU

TRANSCRIPTION RNA pol reaches termination signalReleases both DNA and new mRNA transcript

TRANSCRIPTION AND TRANSLATIONhttp://www.youtube.com/watch?v=41_Ne5mS2ls

BELLWORK ASSIGNMENTTake out your notes, draw, and fill in the table below

Transcription DNA replication

Enzyme used

Polymer made

Number of template strands

Transcription DNA replication

Enzyme used RNA polymerase DNA polymerase

Polymer made RNA DNA

Number of template strands

One Two

DNA RNA PROTEINUp until now we’ve gone from DNA to mRNA through

transcriptionNow, we are going to translate the code in the mRNA into a

sequence of amino acidsWe are changing the language. Hence the name: Translation

THE GENETIC CODEGenetic code: the rules that relate how a sequence of

nitrogenous bases corresponds to a particular amino acid Nucleotides are read three nucleotides at a time to code for an

amino acidCodon: three-nucleotide sequence in mRNA that encodes an

amino acid

DECODING DNA64 codons 20 amino acidsSome amino acids are coded by 2, 3, or 4 codons Start codon: AUG (indicates where translation should begin) Code for Methionine (Met)Stop codons (there are 3) end translation Do not code for an amino acid

PAGE 207 IN YOUR BOOK

TRANSLATION PRACTICE

Translate the following sequences of mRNA (write the first three letters of the amino acid: Methionine = Met)

AUG-AAA-GGG-UGAMet- Asp- Gly

AUG-CGU-GCA-UGC- CGU-GCA-UGA-UUG-CMet- Arg- Gly- Cys- Arg- Ala

AG-AUG-AAG-CUG-CAU-GCA-UGC-UAG-U Met-Lys- Leu-His- Ala- Cys

AUG-CGU-GGG-GUA-UAAMet- Arg- Gly- Val-

UGAUGGAUGAAACCUGAGGU Met-Asp-Glu-Thr

TRANSLATION

Where? cytoplasm5 steps1. Ribosome attaches to mRNA at AUGtRNA anticodon attaches

to complementary mRNA codon

Anticodon: sequence of 3 nucleotides on tRNA that are complementary to the mRNA codon

First amino acid: Methionine

TRANSLATION

2. Next tRNA comes in and binds to codon Peptide bond forms b/w

Methionine and next amino acidRibosome moves to next codon

TRANSLATION

3. First tRNA detaches and leaves Met behindRibosome continues to move down and

elongation of polypeptide chain continues to grow

TRANSLATION 4. Process ends when ribosome reaches a stop codon

TRANSLATION 5. dissasembly: ribosome complex falls apart

Several ribosomes translate the same mRNA at the same time

TRANSCRIPTION AND TRANSLATIONhttp://www.youtube.com/watch?v=41_Ne5mS2ls