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DNA →RNA → PROTEINS Chapters 16 & 17. http://faculty.uca.edu/~johnc/mbi1440.htm. http://www.wappingersschools.org/RCK/staff/teacherhp/johnson/visualvocab/mRNA.gif. 1928- GRIFFITH’s EXPERIMENT. Scientists originally thought PROTEINS had to be the genetic material. 12 A.

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DNA →RNA → PROTEINS Chapters 16 & 17

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Dna rna proteins chapters 16 17

DNA→RNA → PROTEINSChapters 16 & 17

http://faculty.uca.edu/~johnc/mbi1440.htm

http://www.wappingersschools.org/RCK/staff/teacherhp/johnson/visualvocab/mRNA.gif


1928 griffith s experiment

1928- GRIFFITH’s EXPERIMENT

Scientists originally thought PROTEINS had to be the genetic material

12 A

Images from: http://microvet.arizona.edu/Courses/vsc610/mic205/griffith.jpg


Dnarna proteins chapters 16 17

1943- EXPERIMENTS BY OSWALD AVERY, MACLYN McCARTY, & COLIN MACLEOD

WITH LIPIDS,

POLYSACCHARIDES,

OR PROTEINS

THERE’S

NO TRANSFORMATION

ONLY NUCLEIC ACIDS

CHANGE THE BACTERIA

SO . . .

NUCLEIC ACIDS

CARRY THEINFORMATION !

http://www.synapses.co.uk/genetics/dnastruc.html


Dnarna proteins chapters 16 17

http://oceanworld.tamu.edu/resources/oceanography-book/Images/BacteriophageCartoon.jpg

1952-Alfred Hershey and Martha Chase

Bacteriophages are viruses that infect bacteria

Phages are made of

DNA surrounded

by a protein coat

http://www.mun.ca/biology/scarr/Chase_&_Hershey_1953.jpg


Dnarna proteins chapters 16 17

HERSHEY CHASE BLENDER EXPERIMENT

http://www.mun.ca/biology/scarr/hersheychase-experiment.jpg


Dnarna proteins chapters 16 17

ROSALIND FRANKLIN and MAURICE WILKINS

Analyzed DNA with X-ray crystallography to try

and determine structure of DNA

1953 - JAMES WATSON & FRANCIS CRICK

used Rosalind Franklin’s X-ray crystallography

images (PHOTO 51) to come up with alpha helix

model for the structure of DNA

http://en.wikipedia.org/wiki/Rosalind_Franklin

http://www.time.com/time/time100/scientist/profile/watsoncrick.html


Double helix

DOUBLE HELIX

Linus Pauling's Triple helix model

http://www.biosciences.bham.ac.uk/labs/minchin/tutorials/lgdna.html


Structure of nucleic acids

Arrow from: http://www.harrythecat.com/graphics/b/arrow48d.gif

STRUCTURE OF NUCLEIC ACIDS

Built from

NUCLEOTIDE

SUBUNITS

  • NITROGEN BASES

  • CAN BE:

    • ADENINEGUANINECYTOSINETHYMINEURACIL

Image by: Riedell

Sugar can be DEOXYRIBOSE (DNA)RIBOSE (RNA)


Dnarna proteins chapters 16 17

DNA has no URACILRNA has no THYMINE

PURINES (A & G) have 2 RINGS

PYRIMIDINES (T, C, & U) have 1 RING

http://student.ccbcmd.edu/courses/bio141/lecguide/unit6/genetics/DNA/DNA/fg4.html

http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/fg29.html


Dnarna proteins chapters 16 17

Subunits come in as TRIPHOSPHATES

Splitting of nucleotide triphosphates provides the energy to link the nucleotides

See animation

http://www.cat.cc.md.us/~gkaiser/biotutorials/energy/adpan.html


Dnarna proteins chapters 16 17

DNA

  • DOUBLE STRANDED

  • Strands run ANTIPARALLEL

  • Backbone = sugars and phosphates

  • Rungs of ladder = nitrogen bases

  • Hydrogen bonds hold sides of ladder together

http://staff.jccc.net/pdecell/proteinsynthesis/antiparralell.gif


Dnarna proteins chapters 16 17

RNA

  • SINGLE STRANDED

  • Folds into 3D shape

  • Backbone = sugars and phosphates

  • Rungs of ladder = nitrogen bases

http://tigger.uic.edu/classes/phys/phys461/phys450/ANJUM04/


5 and 3 ends

5’ and 3’ ENDS

  • 5’ and 3’ ends named for the CARBON


Dnarna proteins chapters 16 17

Erwin Chargaff analyzed DNA from different organisms and found

CHARGAFF’s RULES: A = T G = C

Now know its because:

A always bonds with T

G always bonds with C

A Purine always bonds to a Pyrimidine


Dnarna proteins chapters 16 17

Semi-

Conservative

Conservative

Dispersive


Meselson stahl

Images from: http://instruct1.cit.cornell.edu/courses/biog105/pages/demos/106/unit01/6.dnareplicationmodels.html

MESELSON & STAHL

Grew bacteria for many generations in radioactive (heavy) 15N . . . so all DNA is heavy

Then grow in 14N, centrifuge as generations divide, and check to see where heavy DNA ends up

http://www.sumanasinc.com/webcontent/animations/content/meselson.html


Meselson stahl1

MESELSON & STAHL

Can tell which model

it is by the banding

patterns of DNA molecules

SO WHAT ?

Proved

SEMI-CONSERVATIVE

REPLICATION MODEL

http://www.sumanasinc.com/webcontent/animations/content/meselson.html


Chromosome structure in prokaryotes

Chromosome Structure in Prokaryotes

Approximately 5 million base pairs3,000 genes

Chromosome

E.coli bacterium

Bases on the chromosome

DNA molecule in bacteriasingle circular loop

© Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved


Central dogma of molecular biology how information passes in cells

CENTRAL DOGMA OF MOLECULAR BIOLOGY(How information passes in cells)

http://www.emunix.emich.edu/~rwinning/genetics/pics/dogma.jpg


Dnarna proteins chapters 16 17

http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/fg12.html

Starting place =

ORIGIN OF REPLICATION

Bacteria have one

Eukaryotes-multiple spots

DNA

REPLICATION

FORK


Dnarna proteins chapters 16 17

HOW NUCLEOTIDES ARE ADDED DURING DNA REPLICATION

DNA

REPLICATION

FORK

http://bio.usuhs.mil/biochem4.html


Telomeres telomerase

TELOMERES & TELOMERASE

Image from: AP BIOLOGY by Campbell and Reese 7th edition

Each

replicationshortens

DNA strand

Primer removed but

can’t be replaced with

DNA because no

3’ end available for

DNA POLYMERASE


Dnarna proteins chapters 16 17

  • TELOMERES-repetitive sequences added to ends of genes to protect information in code

  • TELOMERASE can add to telomere segments in cells that must divide frequently

  • Ex: Cells that give rise to sperm & eggs

  • Shortening of telomeres may play a role in aging

  • Cancer cells may have increased telomerase activity which allows them to keep dividing

ANIMATION

http://stemcells.nih.gov/info/scireport/appendixC.asp


Proofreading repair

PROOFREADING & REPAIR

  • Mistakes in final DNA: 1 in 10 billion

  • Mistakes in initial base pairing during replication:1 in 100,000

  • DNA POLYMERASE proofreads each base as it’s added & fixes errors

  • Errors can come from:

    1. “proofreading mistakes” that are not caught

    2. Environmental damage from CARCINOGENS(Ex: X-rays, UV light, cigarette smoke, etc)


Nucleotide excision repair

NUCLEOTIDE EXCISION REPAIR

  • Cells continually monitor DNA and make repairs

  • NUCLEASES-DNA cutting enzyme removes errors

  • DNA POLYMERASE AND LIGASE can fill in gap and repair using other strand

  • Xeroderm pigmentosum- genetic disorder

    • mutation in DNA enzymes that repair UV damage in skin cells

    • can’t go out in sunlight

    • increased skin cancers/cataracts


Dna rna transcription

DNA →RNATRANSCRIPTION


Rna the other nucleic acid

RNA- the Other Nucleic Acid

Made of NUCLEOTIDES

Sugar = ribose

URACIL NOT THYMINE

Single stranded

http://tigger.uic.edu/classes/phys/phys461/phys450/ANJUM04

http://images2.clinicaltools.com/images/gene/dna_versus_rna_reversed.jpg


3 kinds of rna help with info transfer for protein synthesis

3 KINDS OF RNA HELP WITH INFO TRANSFER FOR PROTEIN SYNTHESIS

RIBOSOMAL RNA (rRNA)

Made in nucleolus

2 subunits (large & small)

Combine with proteins to form ribosomes

Bacterial ribosomes differentsize than eukaryotic ribosomes

  • Evidence for ENDOSYMBIOTIC THEORY

  • Medically significant-some antibiotics targetbacterial ribosomes w/o harming host

rRNA and t-RNA images from Image from: Biology; Miller and Levine; Pearson Education publishing as Prentice Hall; 2006

mRNA image from http://wps.prenhall.com/wps/media/tmp/labeling/1140654_dyn.gif


3 kinds of rna help with info transfer for protein synthesis1

3 KINDS OF RNA HELP WITH INFO TRANSFER FOR PROTEIN SYNTHESIS

TRANSFER RNA (tRNA)

ANTICODON sequence

matches CODON on mRNA

to add correct

amino acids during

protein synthesis

AMINOACYL-tRNA SYNTHETASE

Enzyme attaches a specific

amino acid using energy from ATP

http://www-math.mit.edu/~lippert/18.417/lectures/01_Intro/


3 kinds of rna help with info transfer for protein synthesis2

3 KINDS OF RNA HELP WITH INFO TRANSFER FOR PROTEIN SYNTHESIS

MESSENGER RNA (mRNA)

carries code from DNA to ribosomes


Transcription

TRANSCRIPTION

See a video clip aboutTRANSCRIPTION


Dnarna proteins chapters 16 17

  • Prokaryotes- mRNA functional as soon as transcribed

  • Eukarytoes-mRNA is processed before use

SEE PROCESSING VIDEO

Image from AP BIOLOBY by Campbell and Reese


Mrna s require editing before use

mRNA’s require EDITING before use

  • Message in NOT CONTINUOUS

  • INTRONS are removed

Image by Riedell


Mrna editing

mRNA EDITING

snRNPs (small nuclear ribonucleoproteins)

Made of proteins and RNA

Role in the SPLICEOSOME

(Complex that cuts out the

INTRONS and joins EXONS

to make the final mRNA)

RIBOZYMES-RNA molecules

that function as enzymes (pre-RNA can remove its own introns)


Introns exons

INTRONS & EXONS

  • PROTEIN DOMAINS

  • Modular

  • Ex:

    • Active site,

    • site to attach to membrane

  • In many proteins, different exons code for different domains

  • May facilitate evolution of new proteins

    (EXON SHUFFLING)

  • Increased Crossing over

  • Mix & match exons

Image from AP BIOLOGY by Campbell and Reese


Dnarna proteins chapters 16 17

GTP "cap" put on 5’ end- stability and used to bind mRNA to ribosome

  • PolyA "tail" put on 3’ end (AAA)- stability and movement through the nuclear membrane

Image from AP BIOLOBY by Campbell and Reese


Translation protein synthesis

TRANSLATION(Protein synthesis)


Dnarna proteins chapters 16 17

64 possible codons

Code is REDUNDANT“WOBBLES”

Some amino acidshave more than one

codon.

START=AUG(Methionine is 1st)

3 codons for STOP

Section 12-3

Image from: Biology; Miller and Levine; Pearson Education publishing as Prentice Hall; 2006


Dnarna proteins chapters 16 17

http://www.biologycorner.com/bio4/notes/codon.html


Translation

Image from: Biology; Miller and Levine; Pearson Education publishing as Prentice Hall; 2006

 Translation

Section 12-3


Figure 12 18 translation continued

Figure 12–18 Translation (continued)

Section 12-3

Image from: Biology; Miller and Levine; Pearson Education publishing as Prentice Hall; 2006


Translation1

TRANSLATION

How translation works

SEE ANOTHERTranslation Animation


Regulation modification

REGULATION & MODIFICATION

DURING TRANSCRIPTION

  • Proteins affect ability of RNA polymerase to bind to DNA

    AFTER TRANSCRIPTION

  • Speed of editing introns/exons

  • access to transport proteins or speed of transport out

  • Control amount of mRNA degradation by RIBONUCLEASES

    DURING TRANSLATION

  • Polyribosomes (polysomes)

  • Availability of enzymes

  • POST-TRANSLATIONAL MODIFICATION

  • Alter protein (add phosphates, sugars, etc)

  • Cut and join peptide chains


Completing proteins

COMPLETING PROTEINS

  • POLYRIBOSOMES (POLYSOMES)

    • Numerous ribosomes translate same mRNA at same time

    • 3-D folding (1’, 2’, 3’ structure)

    • Chaparonins


Dnarna proteins chapters 16 17

POST-TRANSLATIONAL MODIFICATIONS

  • Some amino acids modified by addition ofsugars, lipids, phosphate groups, etc

  • Enzymes can modify ends, cleave into pieces

    join polypeptide strands (4’ structure)

    Ex: Made as proinsulin

    then cut

    Final insulin hormone

    made of two chains

    connected by

    disulfide bridges

http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/pancreas/insulin.html


Dnarna proteins chapters 16 17

  • 1st to suggest genes dictate phenotypes through enzymes that catalyze specific chemical reactions

  • Postulated that the symptoms of an inherited disease are due to inability to make a specific enzyme

  • Coined term “inborn errors of metabolism” to describe such diseases

  • Beginning of “One gene-one enzyme” hypothesis

  • ALCAPTONURIA- “black urine” disease- defect in enzyme that breaks down amino acid tyrosine

ARCHIBALD GARROD

1902

http://www.personal.psu.edu/faculty/w/x/wxm15/Online/Molecular%20Biology/media/phenylalanine.gifhttp://www.nature.com/bjp/journal/v147/n1s/images/0706466f5.jpg


Mutations

Mutations

  • Point mutations

    • single base change

    • base-pair substitution

      • silent mutation

        • no amino acid change

        • redundancy in code

      • missense

        • change amino acid

      • nonsense

        • change to stop codon

Slide from Explore Biology by Kim Foglia


Point mutation leads to sickle cell anemia

Point mutation leads to Sickle cell anemia

What kind of mutation?

Slide from Explore Biology by Kim Foglia


Sickle cell anemia

Sickle cell anemia

Slide from Explore Biology by Kim Foglia


Mutations1

Mutations

  • Frameshift

    • shift in the reading frame

      • changes everything “downstream”

    • insertions

      • adding base(s)

    • deletions

      • losing base(s)

    • More damaging atbeginning of gene than at end

Slide modified from: Explore Biology by Kim Foglia


Xeroderma pigmentosum

XERODERMA PIGMENTOSUM

  • UV light damage causes

    THYMINE DIMERS

  • Usually repaired

    (Nucleotide Excision repair)

    • Repair enzymes defective

    • Increased skin cancer

    • severe burns in sunlight

    • Must avoid sunlight

AP BIOLOGY by Campbell and Reese

http://www.shadeshort.com/


Dnarna proteins chapters 16 17

REPLICATION

DNA → DNA ____________

DNA → RNA ____________

RNA→ Protein ___________

TRANSCRIPTION

TRANSLATION


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