Download N.S. 100 Lecture 5 - PPT DNA Spring 2009 Assignment Page

Watson
Crick
Franklin
Wilkins
Franklin’s photo below proved
model on left to be correct for DNA
Pauling
Most
important
scientific
paper in
Biology in last
100 years
First time
DNA double
helix seen in
print
By Watson
and Crick,
1953
2 April 1953
MOLECULAR STRUCTURE OF NUCLEIC ACIDS
A Structure for Deoxyribose Nucleic Acid
“We wish to suggest a structure for the salt of deoxyribose nucleic
acid (D.N.A.). This structure has novel features which are of
considerable biological interest.”
From the original
Watson and Crick
article – first published
“double helix” diagram
Proof of
double helix
Summary of a few people involved with DNA:
Pauling and Corey – “telephone pole” model for DNA
Franklin – x-ray photos proved Pauling wrong
Wilkins – gave x-rays to Watson and Crick
Watson, Crick, Wilkins – Nobel Prizes for DNA structure
Watson & Crick
Pauling and Corey
Rosalind Franklin
06
Lise Meitner
Nobel Prize
Otto Hahn
Nobel Prizes
First to discover
structure of DNA
First to describe the
physics to split the atom
Basic Terms:
DNA Nucleotide (monomer)
Subcomponents of nucleotide
sugar = deoxyribose
phosphate
bases – 4 of them
adenine (A)
guanine (G)
cytosine (C)
thymine (T)
Nucleic Acid (polymer) – chain of nucleotides
Double helix – two chains of nucleic acids
Nucleic acid (polymer) = chain of nucleotides (monomers)
B
P
S
B
P
S
B
P
B
phosphate
P
S
S
B
P
Base =
A, G, C, T
sugar
S
B
P
S
Nucleotide
(DNA or RNA)
Sugar
phosphate
base
Nucleic acid
Double helix
of nucleic acid
Nucleotide
Base Pairing in
DNA double helix
G-C
A-T
C-G
T-A
Only one base
pairing is possible
Nucleosome =
protein + DNA
Protein
DNA
Nucleosome
(a)
Nucleosomes
Heterochromatin = inactive DNA = condensed
Nucleosome
DNA
Euchromatin = active DNA = decondensed
Fig. 13.11
DNA
Replication
DNA replication:
One double helix forms two
identical double helices
Double Helix separates
New strands forms
by base pairing
T
A
A
T
C
G
C
A
Double helix separates
G
T
A
T
Base pairing
New nucleotides are
added to the “old”
or original DNA
nucleotides by base
pairing with the
help of enzymes (not
shown here)
Mutant
normal
Fig. 11.08
Protein
Synthesis
Review
Protein gives life structure
Protein gives life function
Amino acid sequence gives
protein its structure and
function
Question:
How is amino acid sequence
determined?
Yeast
6034 genes
Fruit Fly
Worm
Green Plant
13,061 genes
19,099 genes
25,000 genes
Gene = section of DNA that codes for
amino acid sequence in a protein
DNA
Transcription
(m)RNA (copy)
Translation
Protein
Overview
Retire
already!!!
Sugar–phosphate
backbone
Base pairing is the
genetic code
G-C
C-G
A-T
T-A
DNA double helix separates
RNA nucleotides attach to DNA
T replaced by U
Base pairing makes RNA copy of DNA
Transcription = (m)RNA copy of one side of DNA
Transcription of mRNA
DNA
mRNA transcript
DNA
Codon =
three RNA
nucleotides =
code for particular
amino acid
Translation – conversion of mRNA nucleotide
sequence (codons) into amino acid sequence of protein
Codon – group of three
mRNA nucleotides
Each amino acid has at
least one specific codon.
Alanine (Ala) has the
codon GCU.
Glycine has the codon
GGU
Tyrosine has the codon
UAU
review
Codon =
three RNA
nucleotides =
code for particular
amino acid
Translation =
mRNA codons place amino acids in proper order
review
Nontranscribed strand
5’
Transcription
DNA
3’
Transcribed strand
Codon 1
Codon 2
Codon 3
Codon 4
Codon 5 Codon 6
Polypeptide
Translation
UV-B
UV-A
Sun
screen
products
Human skin
A
C
G
T
T
C
C
A
T
G
C
A
A
G
G
T
Thymine Dimer mutation
DNA from U.V. light
UV light
A
C
G
T
T
C
C
A
T
G
C
A
A
G
G
T
Thymine dimer
Thymine dimer
removed DNA
repair enzymes
New DNA
replaces hole
left by
damaged DNA
Every cell in the body has the same DNA, but each
specific type of cell makes proteins unique to those cells?
In other words every cell in your body has the
exact same book of blueprints but only certain
pages are read in certain cells.
Human embryos are
totipotent = can
become any cell in the
human body
Why?
because it has DNA to
make every cell in the
body.
http://www.dynamist.com/aaa/blastocyst.gif
6 day old embryo
is totipotent –
produce all cells
4 week old
embryo is
pluripotent –
produce most
cells
Salamander – many tissues can
be regenerated if damaged.
Salamander can re-grow new
limbs because adult stem
cells behave like embryonic
cells.
http://www.luc.edu/depts/biology/dev/regen.gif
Heterochromatin - inactive
Salamander leg cells damaged
Nucleosome
Euchromatin - active
DNA
Transcription of DNA
to make new leg
Polymerase Chain Reaction
Small amount of DNA left at crime scene
Polymerase Chain Reaction (PCR)
DNA replication
After 20 replications (a few hours) –
over 1,000,000 helices formed
DNA
DNA
Restriction enzyme (Eco R1)
cuts DNA into fragments
DNA fragments loaded into
wells in gel (like Jell-O)
Fragments (-) migrate through gel because of electric current
DNA fragments
have (-) charge
(+)
(-)
DNA fingerprinting –
compares fragments of DNA
formed by restriction enzymes
Like a
barcode
Father #1
Baby’s
DNA
Father #2