Transcript DNA & RNA - East Pennsboro High School

THEIR ROLE IN PROTEIN
SYNTHESIS

Polymer of nucleotides



Deoxyribose
(5 carbon sugar)
Phosphate group
Nitrogen base






Adenine
Guanine
Thymine
Cytosine
Hydrogen bonds
Double helix - two
strands twisted


Sides – alternating sugar
& phosphate grps
5’ end


3’ end


phosphate
sugar
Steps – base pairs



Adenine – Thymine
Cytosine – Guanine
Connected by H-bonds

Blue prints for life


Carries an organisms
genetic code
Carries instructions
for making proteins:
 Immunology
 Metabolism
 Respiration
 Energy/Storage

Found in nucleus of
cell

Make a copy of DNA


Occur prior to cell
division
Steps:


Enzyme DNA
polymerase unzips
DNA
Two new
“complimentary”
strands built

Single strand




Sugar – ribose
Phosphate grp
Uracil replaces
Thymine
3 Types



Messenger (mRNA)
Ribosomal (rRNA)
Transfer (tRNA)



Process used to make
mRNA from DNA
Occurs in nucleus
RNA polymerase


Enzyme splits DNA
so RNA can form
Role of mRNA

Carries directions
making protein to the
ribosome

Promoter


Section DNA where
enzyme attaches
TATA Box
Repeating sequence
bases – signals where
transcription should
begin
 Immediately
followed by start
codon  AUG


CODONS –
Groups 3 bases code
for an amino acid
 AUG – “start” codon,
codes for methianine
 64 different “3-letter”
codes for 20 different
amino acids


Terminator – stop
signals

UGA, UAA, UAG


Assembly of amino acids at the ribosome to produce a
protein
Initiation – joining of mRNA, tRNA & ribosome

Elongation – the
joining of amino acids



tRNA bring A. acids
to ribosomes
Anticodons on tRNA
match to codons on
mRNA
Termination –
production A. acid
stops – no tRNA to
match STOP codon
DNA
TAC GCT AAG ACT
 MRNA


A. ACIDS

TRNA


Single base is changed – change in 1 a. acid
Silent (no change A.Acid) or result in disease

Insertion


Deletion



Addition of base
Removal of base
Both types result in
change of entire
amino acid sequence
Cytosine insertion on
chrom. 16 believed
cause Crohn’s disease