Download Protein Synthesis: Transcription & Translation

Protein Synthesis:
Transcription & Translation
DNA > mRNA > ribosome > protein
Protein Synthesis Overview
• Two processes are required:
– 1.
– 2.
Transcription: DNA > mRNA
Transcription:
-
• Steps of Transcription
1. DNA strands unwind & separate
2. DNA strand containing a specific gene
serves as a template strand
3. RNA nucleotides are matched to
complimentary DNA bases
4. mRNA molecule is complete and DNA
rewinds
• The bases of mRNA pair with DNA
bases but RNA replaces T with U
DNA
A
T
G
C
• DNA:
• mRNA:
RNA
U
A
C
G
CTG TAC GGA
---> Transcription
GAC AUG CCU
template
strand
Transcription
• mRNA leaves the nucleus
Translation: mRNA > protein
• Process of making
proteins from info
on mRNA
– mRNA travels out of
nucleus to the
ribosome, which
“reads” the mRNA
as a series of 3 letter
words called codons
• Codon: 3-base code on mRNA that
codes for a specific amino acid
– Ex. CGU = alanine
GUU = valine
• The sequence of bases in DNA tell
mRNA what order amino acids must
join together to make a particular
protein.
Codons
found in
mRNA
Third Base
First Base
Second Base
• Transfer RNA (tRNA) matches up with
each codon and transfers the correct
amino acid
• Each tRNA molecule has 3 unpaired
bases called the anticodon that is
complementary to one mRNA codon.
• Each amino acid is added to a growing
chain of amino acids
• Protein = peptide bonds connecting amino
acids
– Many different types of proteins exist because
the number and sequence of amino acids can
be different
Second Base
First Base
Practice translating
mRNA into amino acids:
mRNA: AUG AAA AGU UGU CUG GUU UAA
A.A:
Met - Lys – Ser - Cys – Leu – Val - Stop
______________________________________
Third Base
Codons found
in mRNA
How DNA determines proteins
• DNA molecules serve as templates for making
messenger RNA molecules
• Messenger RNA molecules move to ribosomes
• Transfer RNA molecules bring amino acids to the
ribosome
• Polypeptides (proteins) are formed as ribosomes
move along the messenger RNA strand
Gene Expression
• DNA in all of your body cells is the same!
– Ex: DNA in your eye cells is the same DNA
that is in your skin cells.
• Different types of cells express different
genes.
– Ex: Your eyes may be green, while your skin
is brown.
• Specialization of cells is due to different
patterns of gene expression, rather than
different genes themselves.
– Liver cells express different genes than blood
cells
• DNA:
TAC TCC AGC GCA ACT
----Transcription---->
• mRNA: AUG AGG UCG CGU UGA
----Translation--->
• A.A.:
met arg ser arg stop
Learning Goals
• 1. Summarize the overall process of protein
synthesis including the “central dogma
rule”.
• 2. Describe Transcription in detail including
where it takes places and the roles of
introns and exons.
• 3. Describe Translation in detail including
where it takes place, codons, anti-codons,
tRNA, amino acids, and protein
• 4. Explain how gene expression works.