Transcript Part 2 - Latona

Ch 12-3 Notes, part 2
The Central Dogma =
Protein Synthesis
II. Genetic Code
A. The CODE is located in DNA (stays in nucleus)
B. The code is transcribed from ½ the DNA ladder into a
single stranded RNA
C. mRNA holds the code in CODONS
D. A codon is three (nitrogen) bases long
E. There are ________ possible combinations- (_____)
Ex.
DNA = T G C C A G T G G
mRNA = A C G G U C A C C
mRNA codons are read as = ______ ______
_______
1. Read
from
CENTER
of circle
out
toward
edges
3. Which AA’s
Are found on
The chart twice?
2. What are the
2 possible
Codons for
phenylalanine?
4. Name
stop
codons
D. Codons code for SPECIFIC amino acids.
1. There are _____ amino acids
2. There are _____ codons
3. Each codon represents an amino acid
4. Some amino acids have more than one codon.
5. There is one start codon- AUG which also
codes for the aa – methionine ( this is
usually the 1st aa in a protein)
6. There are 3 stop codons- UAA, UAG and UGA
=Protein synthesis
IN NUCLEUS
IN RIBOSOME
III. Protein Synthesis-2 Parts
A. TRANSCRIPTION-in the NUCLEUS
A. TRANSLATION-in the RIBOSOMES
(ALL OF THEM)
IV. Transcription making RNA from DNA in the nucleus
A. Initiation: RNA polymerase opens up a section(Gene) of
the DNA strand which is signaled with the start codon.
B. Elongation: RNA nucleotides move in to make a
complementary copy from DNA
NOTE*:
-RNA is always single stranded and shorter than DNA
because it is a complementary copy of ONLY ONE
gene.
-All three types of RNA are produced by transcription,
we will focus on mRNA.
D
N
A
m
R
N
A
t
R
N
A
Or
r
R
N
A
D
N
A
C. mRNA is edited
1. Introns are REMOVED
a. used to be thought of as
junk DNA.
b. Now believed to allow cells
to pick and choose which
exons/genes will be
transcribed, therefore which
proteins are made.
2. Exons remain and are
spliced together to become
genes that are expressed.
What do exons do?
Code for Genes/proteins
3. Cap and tail added to finish
D. Once mRNA is edited. Transcription is
finished.
E. The instructions for one GENE has
been copied
F. mRNA can now leave the nucleus and
travel to the ribosome where
Translation can begin.
V. The Genetic Code
A. The mRNA strand is carrying the instructions
from DNA for making a protein.
B. The mRNA copy is used to make proteins in
the process of TRANSLATION
Part 2
of
The Central Dogma
VI. TRANSLATIONmaking proteins in the
ribosome!
A. INITIATION1. AUG on mRNA signals the start of
translation.
2. The mRNA enters the ribosome complex
(ribosome + rRNA) and the first tRNA with the
complementary anticodon (UAC) and amino
acid (methionine) also enter the ribosome
complex.
B. ELONGATION: This is when the
polypeptide chain is growing
1. A second tRNA anticodon attaches to the next mRNA
codon.
2. The enzyme Ribozyme catalyzes a reaction that creates a
peptide bond between the first two amino acids.
3. The order of amino acids is determined by the mRNA
codons, which came from DNA.
Elongation
PHENYLALANINE
METHIONINE
RIBOSOME
mRNA
Start codon
tRNA
lysine
4. The enzyme Ribozyme creates a new ___________ bond to
attach the amino acid to the polypeptide.
5. This process continues like an assembly line as the mRNA
strand moves through the ribosome complex from the 5’ to the 3’
end.
lysine
tRNA
Translation direction
C. Termination- The final step in
proteinPeptide
synthesis.
bond
1. A stop
codon
Amino
signals theacids
finished leave
polypeptide
to be
released
from the
ribosome
complex.
Polypeptide chain
ribosome
tRNA
R
i
b
o
s
o
m
e
s
a
r
e
c
u
t
e
2. The polypeptide may or may not join with
other chains, then it begins folding into its
unique 3-D shape.
** Remember there are many ribosomes in each
cell, and this is occurring all the time in each of
them!
VII. Proteins become either functional or
structural.
A. Name 3 structural proteins.
B. Name 3 functional proteins.
C. What makes one protein
different from another?
1. TYPES, NUMBER, and ORDER of
amino acids in the chain.
3. # of Polypeptide chains of which
they are composed.
4. Type of folding
a. 2 folds-secondary protein
b. 3 folds-tertiary protein
c. 4 folds-quaternary protein
United Streaming “Messenger RNA,
Transfer RNA and Protein Synthesis”
• ADD TO FINAL EXAM REVIEW!
• INITIATION
• ELONGATION
• TERMINATION….
A. INITIATION
1. RNA POLYMERASE
(RP) recognizes a promoter
on the DNA sequence
– PROMOTER: Nitrogen
base sequence that
signals the start of a
gene (AUG)
2. DNA is split by RP and
one strand is used as a
template to build a
complementary RNA
B. ELONGATION:
1. During this stage, a polypeptide is increasing in
length.
a. For each codon, the ribosome verifies tRNA and mRNA
are complementary, and the enzyme ribozyme creates a new
peptide bond to attach the amino acid to the growing peptide
chain.
C. TERMINATION
1. The final step in protein synthesis.
a. A stop codon signals the finished polypeptide to be
released.
b. The polypeptide may or may not join with other chains,
then it begins folding into its unique 3-D shape