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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

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

slide3
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 THE INFORMATION !

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

slide4

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

slide5

HERSHEY CHASE BLENDER EXPERIMENT

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

slide6

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)

slide9

DNA has no URACIL RNA 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

slide10
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

slide11
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

slide12
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
slide14
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

slide15
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

slide20

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

Starting place =

ORIGIN OF REPLICATION

Bacteria have one

Eukaryotes-multiple spots

DNA

REPLICATION

FORK

slide21
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

slide23
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
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

slide32
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

slide36
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

slide38

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

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
slide45
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

slide46
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/

slide52

REPLICATION

DNA → DNA ____________

DNA → RNA ____________

RNA→ Protein ___________

TRANSCRIPTION

TRANSLATION

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