Download Genes

Gene
Expression
SEC 25.2 PG 510-516
Rapid Review…
 Last Class: DNA & Replication

What enzyme is
used in STEP 1?

What do it do &
accomplish?

What happens in
Step 2?

Where do these
materials come from

What enzyme is in
step 3? What does it
join up?

Why is the process
“semiconservative”?
Replication Video
Why must DNA Replication occur?
What’s the link between the
images to follow and the words
DNA….
GENE…
PROTEIN…
AMINO ACID…
BEGIN WITH I WONDER…
Let’s Take
another look
"Parenthood is about raising and celebrating the child you
have, not the child you thought you would have. It's about
understanding that he is exactly the person he is supposed to
be. And that, if you're lucky, he just might be the teacher who
turns you into the person you are supposed to be.” -Joan
Ryan
Ava’s health quirks are due to an eight base-pair deletion
(c.1547_1554del8) on her CDKL5 Gene
This Is called the CDKL5 disorder& is also refered
to Atypical Rett Syndrome .
CDKL5 is a kinase gene which are regulators of cell function
UGG
Must be…
 U:
uracil
 G: guanine
 G: guanine
MUST
BE RNA!
PKU
 Loss
of mental functioning
 Due to faulty enzyme
Unable to convert
phenylalanine to tyrosine
 Cannot break down proteins
Translation

The message in DNA is copied into RNA then must
be TRANSLATED into the order of amino acids
Mutations

Changes in the order of amino acids can be

Good

Bad

No effect

Abinism: faulty enzyme, cannot covert tyrosine
into melanin

Result: No Natural pigment in skin
The Genetic Code
Gene:
 a short section
of DNA that
codes for a
protein
 Codes for the
order of amino
acids
Genes
 The
order of bases in DNA codes for
amino acids
 The
bases can be re- arranged to
make 20 different amino acids!
 Every
3 bases code for 1 specific
amino acid
HOW?
PROTEIN
AMINO
ACIDS
CODONS
WORDS
SENTENCES
CODONS
A
group of 3 bases that code
for an amino acid
Example:

AUG
codes for methionine.
Amino Acids and Codons
50
Cents favourite codon:
UAG
Gene Expression:
From DNA  RNA Protein
Simplified Overview:
DNA unwinds
2. an RNA copy of the gene is made
3. RNA leaves the nucleus & carries the
message into the cytoplasm
4. RNA attaches to a ribosome
5. Code is “read” & “translated” into amino
acids
6. The correct order of amino acids are
brought to ribosome.
7. Amino acids join up = PROTEIN
TADAAAA!!!!
1.
Three Types of RNA needed to
make a Protein:
1.
Messenger RNA (mRNA):
Carries the code from DNA in the nucleus out to a ribosome
in the cytoplasm
2. Ribosomal RNA (rRNA)
 Forms
one of the 2 subunits needed to
make up a ribosome
 site
where polypeptides (proteins) are
made
3.Transfer RNA (tRNA)
 Brings
the amino acids to the ribosome
 Helps translate the message!
 Made of a single RNA Strand folded
in “t shape”
 Picks up & binds
Amino acids on
one end
 Attaches to
mRNA at
other end
Understanding the Details…
2 main events:
I.
TRANSCRIPTION
II.
TRANSLATION
I. Transcription:“to make a close copy”

makes an RNA molecule that is
complimentary to the DNA segment
 DNA
sequence:
AAGCT
 RNA
complimentary sequence:
UUCGA
 ENZYME:

RNA polymerase
splits apart the DNA and joins the RNA
nucleotides together
 mRNA
is made & exits the nucleus!

transcription
LAST CLASS:
TODAY:
Transcription!
Translation!
One thing to add…
re: transcription
PROCESSING of mRNA
 There
are some “non-coding” regions on the
DNA/mRNA copies
 Introns:
sections that don’t code for genes
 Introns
are removed before mRNA leaves the
nucleus
 mRNA
contains only EXONS:
 codons
for proteins that will be “expressed”
II. Translation:“to put info into a different language”
 mRNA message is translated into a protein!
II. Translation
II. Translation: “to put info into a different language”
 Amino
acids are brought to ribosome by
tRNA & form a growing polypeptide
 REQUIREMENTS:
 Ribosome
 mRNA,
 Amino
rRNA & tRNA
acids
What do you
see in this
picture?
Detailed Steps of Translation
Initiation:
I.
•
The codon “AUG” ( methionine) occurs
on the mRNA strand and signals START
•
tRNA- brings the correct amino acid to the
mRNA strand
• tRNA attaches to mRNA at it’s anticodon
ANTICODON:
•
Area at bottom
of tRNA
•
3 bases that are
complementary
to mRNA
•
Binding site to
mRNA
Enzyme:
tRNA- synthase
•
Helps join correct
amino acid to tRNA
•
Requires ATP
Amino Acid
tRNA synthetase helps
bind the amino acid to
the tRNA molecule
tRNA
Anticodon
mRNA strand codon
Understanding Codes…
DNA:
AGCTTGCAA
mRNA:
UCGAACGUU
ANTI-CODONS:
A G C U U G C AA
Amino Acids? p511
serine, asparagine, valine
II.
Elongation

one amino acid at a time is added
Polypeptide gets longer

Each ribosome has space for 2 tRNAs at once

III. Termination
 “STOP”
 “Cut
codon (UAA, UGA or UAG) is read
n Release”
 Enzyme
cuts polypeptide off
 Ribosome
separates & falls off mRNA