Transcript Nucleic Acids and

Nucleic Acids
and
Protein Synthesis
Nucleic Acids
 DNA
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Deoxyribonucleic Acid
 RNA
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Ribonucleic Acid
DNA
Double
stranded helix
Never leaves the nucleus
Watson, Crick, Wilkins
won Nobel Prize in 1962
Franklin died in 1958
never recognized
DNA
Nucleotide
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Building Blocks of nucleic acids are
NUCLEOTIDES!
 Phospate group
 Sugar molecule (deoyribose)
 Nitrogenous bases
Nitrogenous Bases of DNA
How do the N-Bases pair up?
A-T (2 bonds)
 G-C (3 bonds)
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How Does DNA Replicate?
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1. double helix unwinds
2. Each chain serves as a template for new
nucleoide chain
3. point at which 2 chains separate is called the
REPLICATION FORK.
4. HELICASE = the enzyme that separates the
chains (breaks H bonds)
5. DNA POLYMERASE moves along the chains and
helps assemble new nucelotides forming new chains
(3’ to 5’ ONLY)
DNA LIGASE – ligates 5’ to 3’ (DNA polymerase
brings the nucleotides)
DNA replication continue…
The 3’ sugar has an –OH GROUP
 The 5’ sugar has a PHOSPHATE GROUP
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LEADING STRAND – formed from 3’-5’
 LAGGING STRAND – formed from 5’- 3’
with the help of DNA LIGASE!
 OKAZAKI FRAGMENTS – fragments that
will be ligated together
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Can you see how DNA is making
an exact copy of itself!
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This a little more difficult
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Can you figure out the diagram?
Simplest Illustration of DNA
replication…
What is a
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mutation??
A CHANGE in the
nucleotide sequence at
even ONE location!!
RNA
RIBONUCLEIC ACID

SINGLE STRANDED
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RESPONSIBLE FOR BRINGING THE
GENETIC INFO. FROM THE NUCLEUS
TO THE CYTOSOL!
RNA Nucleotide
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Phosphate group
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Sugar molecule (ribose)
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Nitrogenous bases
Adenine – URACIL
 Cytosine - guanine
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3 Kinds of RNA
mRNA – (messenger) brings info from
DNA in nucleus to cytosol in eukaryotic
cells (uncoiled)
 tRNA –(transfer) brings amino acids to
mRNA for translation (hairpin shape)
 rRNA –(ribosomal) most abundant, rRNA
makes up the ribosomes where proteins
are made (globular)
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TRANSCRIPTION!!
DNA  RNA
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1.RNA polymerase-initiates transcription by
binding to region on DNA called PROMOTER
(causes DNA to separate)
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2. only ONE of the DNA chains will be used for
transcription it’s call the TEMPLATE
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3. RNA POLYMERASE – attached to first DNA
nucleotide of template chain – then begins
adding complementary RNA nucleotides
Cont. Transcription
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4. transcription continues until RNA
polymerase reaches a TERMINATION
SIGNAL on the DNA
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5. RNA polymerase releases both the
DNA mol. And newly formed RNA mol. Are
transcribed in this way (all three!!!)
RNA
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RNA replications
Protein Synthesis
PROTEINS
CARRY OUT
THE GENETIC
INSTRUCTIONS
ENCODED IN AN
ORGANISM’S DNA!!!!
TRANSLATION
The process of assembling from
info. Encoded in a mRNA!
1. mRNA leaves nucleus
 2. mRNA migrates to ribosome in cytosol
for protein synthesis
 3.amino acids floating in cytosol are
transported to ribosomes by tRNA mole
 4. peptide bonds join the amino acids to
make polypeptide chain
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Vocabulary!
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1. GENETIC CODE: correlation between a
nucleotide sequence and an amino acid
sequence
2. CODON
3 mRNA nucleotides, codes for
a specific amino acid (64)
3. START CODON (AUG) & a.a. methionine
4. STOP CODON (UAA, UAG, UGA)
5. ANTICODON – 3 tRNA nucleotides carrying
a specific amino acid!
Protein Synthesis
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Protein Synthesis
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Protein Synthesis
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THE SUMMARY!