Download CHAPTER 10 NUCLEIC ACIDS: DNA & RNA

CHAPTER 10
MOLECULAR GENETICS
NUCLEIC ACIDS to
PROTEINS:
•STRUCTURE
•REPLICATION
•PROTEIN SYNTHESIS
DNA is the unit of heredity.
it is transmitted from
parents to offspring in
reproductive cells called
gametes. (meiosis)
CHROMOSOMES are…
DNA coiled around HISTONE
proteins then supercoiled into
a compact shape. This is
important for cell division.
1953
FRANKLIN, WATSON & CRICK
discovered the structure of DNA
(NOT ON TEST… just thought you’d like to know)
X-ray diffraction crystallography is a technique that was used
to help scientists learn the structure of DNA. (Rosiland Franklin)
Double stranded
DNA
STRUCTURE
– 2 polymer chains of
nucleotide
monomers
– Covalent bonds
joining amino acid
monomers “sugar
phosphate
backbone”
– Hydrogen bonds
joining the two
strands through
nitrogen-containingbases “A”, “T”, “G”
or “C
Unit of Heredity
FUNCTION
– Easily copied
(Sphase)
– 2 template strands
– Gene copied into
mRNA is
instructions to
assemble protein.
THE DOUBLE HELIX
sugar-phosphate
backbone or
“uprights” of
the
ladder
base-pairs
are the “rungs”
of the ladder
DNA NUCLEOTIDES
DeoxyriboNucleic Acids
are made of 3 parts:
1. Phosphate Group
2. Sugar = deoxyribose
3. Nitrogen-containing
base:
• A (adenine)
• T (thymine)
• G (guanine)
• C (cytosine)
RNA NUCLEOTIDES
RiboNucleic Acid
are made of 3 parts:
1. Phosphate Group
2. Sugar = RIBOSE
3. Nitrogen-containing
base:
• A (adenine)
• U (uracil) instead of
T
• G (guanine)
• C (cytosine)
Nitrogen
Containing
base
phosphate
group
sugar
The nucleotide is the chemical building block of NUCLEIC ACIDS
There is no THYMINE base in
RNA
URACIL takes it’s place
URACIL is a molecular mimic of
THYMINE and does it’s same
job
Base-Pair Rules or
Chargaff’s LAWS:
pyrimidines
(T & C)
purines
(A & G)
1. purine-pyrimidine
2. Adenine-Thymine
Thymine-Adenine
3. Guanine-Cytosine
Cytosine-Guanine
RNA
Uracil-Adenine
Adenine-Uracil
Each nucleotide’s
partner is called it’s
COMPLEMENT
•
•
•
•
•
•
•
•
•
•
•
•
•
A
T
G
C
A
T
C
C
A
G
C
T
T
Tell me the complements to this nucleotide sequence….
Each nucleotide’s
partner is called it’s
COMPLEMENT
•
•
•
•
•
•
•
•
•
•
•
•
•
A
T
G
C
A
T
C
C
A
G
C
T
T
A
A
G
C
T
A
A
G
C
U
G
C
G
C
A
A
T
G
U
C
C
G
A
T(
A
U
Chargaff’s Rule… The amounts of A & T match, so do the
Amounts of C & G (where the base-pair rules came from).
if the DNA is 35% A, then…
What are the values for T, C, G?
•
•
•
•
If A = 35% and A = T… then T=35%
Since 35+35=70 and 100-70=30, G+C=30
If G=C… then G = 15% and C = 15%
ANSWER:A= 35%, T= 35%, G = 15%, C= 15%
• QUESTION: What are the values of A,T,G, and C
if the DNA is 20% G?
• ANSWER: A=30%, T=30%, G=20%, C=20%
• QUESTION: What are the values of ATC&G if
the DNA IS 10% T?
• ANSWER: A=10%, T=10%, G=40%, C=40%
DNA REPLICATION- copying the DNA.
ENZYMES USED:
•HELICASE-open DNA
•DNA POLYMERASE-build polymer
•DNA LIGASE-connect fragments
NUCLEOTIDES USED:
•DNA NUCLEOTIDES base-pair rule
SEMICONSERVATIVE
REPLICATION:
•2 strands: each is 1/2 old & 1/2 new
•Leading strand- continuous
•Lagging strand- okazaki fragments
•Polymerase moves along the template strand
in a 3’ to 5’ direction.
•New strand is built 5’ to 3’
The 5’ end has the phosphate
Notice, the two strands run
anti-parallel (opposite).
SEMICONSERVATIVE
REPLICATION…
each strand of the DNA
double helix
acts as the “template” or
instructions to build the
matching strand
Mutations do
occur but are
fixed by enzymes.
1/100,000
nucleotides are
incorrectly placed
Enzymes fix most
mistakes reducing
the number to
1/ billion base pairs
Mutations (changes in the DNA
sequence) can mean changes in
phenotypes. They are the fuel for
evolution.
What is the connection between
your genes (genotype) and how
you look (phenotype)???
PROTEIN
PROTEIN SYNTHESIS
Central dogma = DNA --> RNA --> protein
DNA (instructions) REMAIN IN THE NUCLEUS
PROTEINS ARE ASSEMBLED OUTSIDE THE NUCLEUS on RIB
DNA… the instructions
• double stranded
• twisted shape
RNA… the workers
mRNA- single stranded
rRNA- globular form
w/ proteins
tRNA- single stranded,
hairpin
loop
PROTEIN… the
molecular
model of
tRNA
I made
while
working
at my old
Job.
TRANSCRIPTION
making mRNA, tRNA, and rRNA
The promoter has the sequence TAC which causes the RNA polymera
to attach to the beginning of the template chain and mRNA to be made
The terminator sequence causes the RNA polymerase to release both
the DNA and the newly formed mRNA.
There are 3 different terminator signals: ACT, ATT, and ATC.
TRANSCRIPTION
TRANSLATION
•3 types of RNA work together to produce
proteins
• proteins are chains of amino acids bonded
together by peptide bonds
TRANSLATION
• Ribosome attaches to start
codon on mRNA (AUG).
• 1st tRNA w/ anticodon (UAC)
binds to start codon w/in
ribosome.
• 2nd tRNA w/ matching
anticodon to 2nd codon binds.
• Peptide bond is formed
between amino acid #1 and
amino acid #2.
• First tRNA leaves.
• Ribosome moves to next codon
on mRNA and tRNA #3 moves
in…. Peptide bond.REPEAT
• When stop codon is reached
(UAA, UGA, UAG) release
factor breaks binds instead of
tRNA.
How can 4 nucleotides code for
20 different
proteins??????????????
read the nucleotides as sets of three
3
(4)
4 x 4 x 4 = 64 combinations
codon
anticodon
Nucleotides have meaning in sets of THREE.
Don’t
Be
tricked
The CODE can be cracked using this table. Use it to determine whic
of the 20 amino acids each mRNA codon- codes for.
WHICH AMINO ACID?
1) DNA Triplet is TTT
2) Codon is AUG
3) Anticodon is CCC
4) ACT
WHICH AMINO ACID?
1) DNA Triplet is TTT
2) Codon is AUG
3) Anticodon is CCC
4) ACT
OK… I will!
ANSWERS:
1) Lys
2) Met
3) Gly
4) STOP
…G A T T A C A T A…
…C T A A T G T A T…
DNA
TRIPLET
GAT
TAC
ATA
mRNA
CODON
tRNA
Amino Acid
ANTICOD
ON
A
A
U
…G A T T A C A T A…
RNA polymerase
DNA
TRIPLET
GAT
TAC
ATA
G
mRNA
CODON
C
A
U
U
A
RNAnucleotides
tRNA
Amino Acid
ANTICOD
ON
A
A
U
…G A T T A C A T A…
RNA polymerase
G
DNA
TRIPLET
mRNA
CODON
GAT
CUA
TAC
AUG
ATA
UAU
C
A
U
U
A
RNAnucleotides
tRNA
Amino Acid
ANTICOD
ON
A
A
U
…G A T T A C A T A…
RNA polymerase
G
C
A
U
DNA
TRIPLET
mRNA
CODON
GAT
CUA
TAC
AUG
UAC
ATA
UAU
AUA
U
A
RNAnucleotides
tRNA
Amino Acid
ANTICOD
ON
GAU
1. WRITE THE
CORRECT LETTER
BELOW EACH
SYMBOL.
2. USE “BASE PAIR”
RULES TO WRITE
THE mRNA
3. TRANSFER THE
CODONS BELOW.
4. USE “BASE PAIR
RULES” TO WRITE
THE ANTICODONS.
5. USE CODONS &
THE CHART TO
FIND AMINO
ACIDS.
CHECK
YOUR
WORK.
HOW DID
YOU DO?
ANY
QUESTIONS?
YOUR Classwork/
homework… plus the
Other sheets.