Download RNA & Protein Synthesis

RNA & Protein
Synthesis
How does DNA make the proteins
that make living things?
RNA

RiboNucleic Acid
 Made of nucleotides
* 5 carbon sugar
(ribose)
*phosphate group
*nitrogenous bases
(A,U,C,G)

There are 3 types of
RNA:
1) rRNA - (ribosomal
RNA)
2) tRNA - (transfer RNA)
3) mRNA -(messenger
RNA)
Some important differences
between DNA & RNA
1) RNA uses a different
5 carbon sugar!
Ribose instead of
Deoxyribose
2) RNA is a single
strand, DNA is a
double strand
3) RNA uses uracil
instead of thymine
Protein Synthesis
DNAmRNAprotein
Protein synthesis
 Includes
2 processes: TRANSCRIPTION
& TRANSLATION!
 Uses many enzymes…
 Makes a “copy” of instructions from the
DNA and sends those copies to the
ribosome to make a specific protein.
Transcription

Process of making mRNA
from a strand of DNA.

Happens in the nucleus.

Only uses one side of the
DNA

RNA polymerase is the
major enzyme used

Starts at a “promoter” on
the DNA…this is the start
of the gene.

RNA nucleotides are
added to the
complimentary strand on
one side of DNA until the
“termination” portion is
reached.
Transcription
mRNA
 Has
a triplet codon (a sequence of 3
nitrogen bases, like AGC or UAC)
 The
codons code for the same amino
acids in almost all living things.
The Universal Genetic Code
Another way to display it…
Tweaking the RNA
 Some
of the stuff on DNA is “junk”.
 mRNA
is “edited” to cut introns from the
mRNA. (Using special enzymes!)
 The
“good” parts, exons, are kept and
“pasted” together to make the expressed
part of the gene…the stuff that actually
gets made!
Example:
 I’ve
had a bad day. Farleyfarleyfarley
Hafharl. Bolrnt daffigty coombin
snagglefahrt. I sat down on the couch with
a bowl of cereal. Axd nadherul klahsur
gususj! Then, my cat attacked me. Ukl
tolsuie hudla di. She jumped right in the
bowl and started drinking the milk! Can
you believe that? Naah gouu!
 You
get all that?
 Much
of that paragraph is nonsense, just
like much of the DNA.
 Also, just like the DNA, it has to be edited
to make it sensible.
Using the last example…
 I’ve
had a bad day. I sat down on the
couch with a bowl of cereal. Then, my cat
attacked me. She jumped right in the bowl
and started drinking the milk! Can you
believe that?
 The
introns have been removed from the
message and now it is ready to be
expressed.
Switching gears…now on to:
Translation!

Makes a protein using tRNA, enzymes and
mRNA.

Occurs in the ribosome.

tRNA has the anticodon (a matching codon that
allows the tRNA to attach to the ribosome at the
mRNA).

mRNA  Protein
Translation Steps:

1.) Ribosome “reads” the mRNA one codon at a time (3
bases at a time).
2.) Ribosome “calls” the tRNA that has the anticodon to
bring the amino acid.
3.) Amino acid attaches and tRNA is released.
4.) The next codon is read and another amino acid is
brought by tRNA and attached to the 1st amino acid.
5.) This continues until the “Stop” codon is reached.
Translation
mRNA
The Universal Genetic Code
Another way to display it…
Mutations
 …are
any change in the DNA of an
organism.
 May
not have any affect or may cause a
major deformation, illness.
Gene Mutations

Point Mutation


only 1 codon is affected
example: “substitution mutation”
AUC GGA UCC  AUC CGA UCC
THE FAT CAT WAS MAD
THE FUT CAT WAS MAD
More Gene Mutations
 Frameshift


Mutations –
will affect several if not all of the following
codons! (MAJOR PROBLEM!)
Example: “Deletion” – one base was left out.
AAU CGA GGA …  AAC GAG GA…
(What is missing?)
AAU CGA GGA …  AAC GAG GA…
Did this make a difference in the
amino acid sequence???
 AAU
CGA GGA …  AAC GAG GA…
 Find
the a.a. sequence for the right side:
 Asp
– Arg – Gly
 Find
the a.a. sequence for the changed
side:
 Asp – Glu – (either Glu or Asp)
So what happened?
 The
a.a. sequence changed from:
 Asp
– Arg – Gly
 to…
 Asp

– Glu – (either Glu or Asp)
This is bad. It changes the entire protein, making
the protein not able to do its intended job. (Like
changing the shape of a key makes it not fit in
the lock.)
Back to the Fat Cat…
THE FAT CAT WAS MAD…
THE FAC ATW ASM AD…
Deletions cause a shift in the codons…just
like leaving a letter out, it makes no sense!
Other Frameshift Mutations:

“Insertion” – an extra base is added.
ACC GAU GUC…  ACU CGA UGU C…
(What was added?)
ACC GAU GUC…  ACU CGA UGU C…
THE FAT CAT WAS MAD
THE FAD TCA TWA SMA D…
Once again, this makes no sense!
Chromosome Mutations
 …are
usually damaging.
 An
entire piece of a chromosome may be
deleted, moved or damaged.
 ALL
INFORMATION ON THE AFFECTED
SECTION MAY BE LOST OR FOREVER
CHANGED (and is useless).
Types of Chromosome Mutations

Deletion – the whole chromosome is gone!
Duplication – now you have 2 sets of the same
stuff.
 Inversion – one part of a chromosome gets
moved to another area on the SAME
chromosome.
 Translocation – a section of a chromosome is
stuck on a DIFFERENT chromosome

Chromosome Mutations