Download Building Proteins - Marblehead High School

Building Proteins
From RNA to protein
molecules
12-3
By the end of this lesson, you
should be able to:
1)
2)
3)
4)
5)
6)
Tell how DNA differs from RNA
Compare the 3 types of RNA
Describe the process of
transcription
Describe the process of translation
Explain the relationship between
genes and proteins
Explain how a mutation occurs
How does the information on the
DNA get used by the cell?
Proteins NEED to
be made!!!
 By who?
 How does the
information get
there?

Genes – sections of DNA that
code for a protein
ONE Gene  RNA  ONE Protein
Types of RNA:
1) Messenger RNA
(mRNA)
2) Ribosomal RNA
(rRNA)
3) Transfer RNA
(tRNA)
rRNA
Types of RNA:



Messenger RNA (mRNA)- carry
instructions on the DNA to the
ribosome
Ribosomal RNA (rRNA)-make-up
the ribosome
Transfer RNA (tRNA)-carries the
correct amino acid to the ribosome
to build proteins
How is it different from DNA?
 Carries
out the cell’s instructions
instead of…
 Is single stranded instead of…
 Contains the sugar ribose instead
of…
 Contains the nitrogenous base Uracil
that binds to adenine instead of….
Process of Transcription
1) RNA polymerase binds to the
promoter region on the DNA
Promoters – nucleotide sequence
that signals the RNA polymerase to
bind to them
2) RNA polymerase separates the DNA
strands
Process of Transcription
3) Following the base pairing rules, the
RNA polymerase adds the correct
sequence of nucleotides to the
growing RNA molecule
4) The RNA strand stops growing when
the RNA polymerase reaches the
STOP signal on the DNA
5) The RNA is edited before it is used
by the cell
RNA editing
Introns – non-coding segments of RNA
Exons – regions of the RNA that code for proteins
Its your turn….
You be the RNA polymerase
binding to this gene
DNA
A T G G C C A T T C G A C G T A
T A C C G G T A A G C T G C A T
RNA
Then what?
1)
2)
3)
The mRNA leaves the nucleus and travels
to the ribosome
Its code is held in groups of three
nucleotides (codons)
One codon codes for one amino acid
UGCACGAUCGCA
is read
UGC-ACG-AUC-GCA
How do you know what amino acid
it codes for?



There are 20 possible
amino acids to choose
from
Example: GGA codes
for Glycine
How about…
– AUG
– UAU
– UAG
Translation



Occurs at the ribosome
De-codes the message on mRNA
Amino acids are bonded together in order to build
a polypeptide (protein)
Steps of Translation:
1) mRNA leaves the nucleus and
travels to the ribosome
2) mRNA attaches to the ribosome at
the start codon
3) tRNA attaches the correct amino
acid to the growing polypeptide (ex:
mRNA reads AUG  methionine is
added)
Steps of Translation:
4) tRNA follows the base pairing rules
and matching the correct anticodon
on the tRNA to its codon on the
mRNA
5) The amino acids join together with
peptide bonds as the ribosome
continues to move down the mRNA
and read its codons
6) The ribosome stops when it
reaches a stop codon on the mRNA
What is the result of translation? Why is it important?
http://phschool.com/webcodes10/index.cfm?wcprefix=cbe&wc
suffix=4123&fuseaction=home.gotoWebCode&x=6&y=14
Uh-oh! Cells can make mistakes!!!!
Mutations:
1) Gene mutation –
changes in a
single gene
1)
2)
3)
Substitution Point mutation
Insertion
Frameshift mutation
Deletion
Mutations
2)
Chromosomal
mutations –
changes in a
whole
chromosome
**Polyploid
individuals have
an extra set of
chromosomes
Your turn:
 Complete
mutations
the 12-4 worksheet on