Transcript RNA and Protein Synthesis

RNA and Protein
Synthesis
Mr. Cobb
GCA Fall 2011
Review DNA
What is a nucleotide?
What shape does DNA have?
What are the nitrogen bases in DNA?
Where do you find DNA?
Review DNA
What is a nucleotide?
Sugar, phosphate, and base
What shape does DNA have?
Double Helix
What are the nitrogen bases in DNA?
ADENINE, THYMINE, GUANINE AND
CYTOSINE
Where do you find DNA?
NUCLEUS
BASE PAIRING
• ADENINE – THYMINE (URACIL IN RNA)
• GUANINE – CYTOSINE
• A–T
• G–C
ALWAYS!!
Complete the DNA strand:
A - ___
T - ___
G - ___
G - ___
C - ___
C – ___
C - ___
G - ___
T - ___
A - ___
G - ___
A - ___
RNA
Ribonucleic Acid
Contains Ribose as its 5-carbon sugar
Single strand-not double helix
Nitrogen Bases are A, C, G, and U
(Uracil)
NO Thymine in RNA!!!!!
If you are looking at:
A strand of bases and you are told to
identify them as DNA or RNA,
IF you see Uracil, you will KNOW
that it is RNA!!!
WHY TALK ABOUT
PROTEIN SYNTHESIS
•
CELL FUNCTIONS DEPEND ON ENZYMES (BIOLOGICAL
CATALYST), WHICH ARE PROTEINS!
•
MOST SUBSTANCES MADE BY CELLS CONTAIN A
PROTEIN.
•
UNDERSTANDING THIS PROCESS, SCIENTISTS CAN
MAKE CHANGES TO WHAT PROTEINS ARE PRODUCED
(ANTIBIOTICS)
PROTEIN REVIEW
•
POLYPEPTIDE CHAINS OF AMINO ACIDS
(AA)
•
21 AMINO ACIDS
•
2 THINGS MUST BE CORRECT FOR PROTEIN
TO BE FUNCTIONAL
•
1. SEQUENCE OF AA
•
2. SHAPE
PROTEIN SYNTHESIS
THE CELL CAN MAKE THOUSANDS OF
DIFFERENT PROTEINS
OR
THE CELL CAN MAKE THOUSANDS OF THE
SAME PROTEIN.
PROTEIN SYNTHESIS
STEPS
•
2 STEPS to making Proteins:
•
STEP 1 TRANSCRIPTION: Getting
the information from the DNA
copied onto a mRNA strand.
•
STEP 2 TRANSLATION: The mRNA
strand goes out to a ribosome and
builds a AA strand with the help of
tRNA.
Protein Synthesis in a
nutshell
Here’s a better look:
THE CODE OF LIFE
•
COMPARE TO ALPHABET
•
DNA’S CODE IS THE 4 NUCLEOTIDE BASES OF
ADENINE, GUANINE, CYTOSINE, AND THYMINE
•
THREE OF THESE BASES COME TOGETHER TO
MAKE A CODE FOR AN AMINO ACID.
THE CODE OF LIFE
•
THREE BASES MAKE A CODON.
•
•
(THINK OF IT AS A 3 LETTER
WORD MEANING A SPECIFIC
AMINO ACID)
A CODON CODES FOR A
SPECIFIC AA.
THE CODE OF LIFE
•
COMPARE TO THE ALPHABET CODE WE DISCUSSED.
•
EX. THE DOG CAN RUN
•
EACH LETTER IS A NUCLEOTIDE BASE.
•
EACH THREE LETTER WORD IS A CODON THAT CODES
FOR A SPECIFIC AMINO ACID.
•
A STRING OF AMINO ACIDS MAKE A FUNCTIONAL
PROTEIN, JUST LIKE A STRING OF WORDS MAKE A
SENTENCE.
THE CODE OF LIFE
•
LETS SEE WHY THE SEQUENCE IS
IMPORTANT!
•
THE RUN CAN DOG
•
ONE AMINO ACID CHANGE CAN CHANGE
THE PROTEIN, JUST LIKE ONE WORD CAN
CHANGE THE SENTENCE.
•
THE CAT CAN RUN
•
THE DOG CAN SIT
•
THE DOG CAN HOP
Amino Acid Chart
Amino Acids
There are 21 Amino Acids, but as you can
see 64 combinations.
So, there are multiple codons per amino
acid.
Also “stop” and “start” codons.
3 kinds of RNA:
Ribosomal RNA (rRNA) –makes up
ribosomes
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Why do we need RNA?
RNA is the key mechanism
behind:
PROTEIN SYNTHESIS
Your characteristics are
determined largely by the kinds of
proteins your cells make out of
amino acids.
PROTEIN SYNTHESIS
Where are proteins made? What organelle?
Where are ribosomes located?
Where are the directions for making proteins
found?
OK, if the directions are in the
nucleus, but the ribosomes are in
the cytoplasm or on the E.R.,
How do the directions get to
the ribosomes????
That’s why we need
messenger RNA (mRNA)
mRNA is made in a process called
TRANSCRIPTION
•
Transcription is “the process of
copying the DNA code onto a strand
of mRNA”
“-scribe” means “write” so the code
is copied or written onto mRNA
during transcription
mRNA
Is made from a DNA strand
pattern.
DNA “unzips” just the section
that codes the directions for
the needed protein.
RNA nucleotides come in and
bind with the DNA nitrogen
bases
So, transcription is
“Writing” the mRNA code from a
strand of DNA
Occurs in the nucleus so the message
can be sent from DNA to the
ribosomes
DNA never leaves nucleus!
Cool facts about mRNA
•
mRNA has a “cap” on one end and a Poly A tail
on the other end.
•
There are parts that are not used caused
“introns” that are edited out before the mRNA
gets to the ribosomes.
•
The “exons” are the parts that are not edited out
and thus used to make the protein.
Here’s a better look:
Now that we have our
message,
The mRNA can move through the
nuclear pores to go to ribosomes
Ribosomes will “read” the mRNA to
build a protein
mRNA moves to ribosome
mRNA is read 3 letters at a time—
codons
So, in our example, the first codon
would be GUA
Codons become important in the
next step
When mRNA gets to the
ribosome:
The third kind of
RNA comes into
play.
Transfer RNA
(tRNA)
Notice the 3-letter
anticodon & amino
acid
TRANSLATION
mRNA is read in codons (3 letters
at a time)
A tRNA anticodon matches up
with the mRNA codon
tRNA has an amino acid attached
at the top
See your amino acid chart
Translation is:
The process of
synthesizing amino
acids into proteins
with the aid of RNA
Protein Synthesis in a
nutshell
Translation
(this is not in the notes)
•
The mRNA brings the DNA blueprints (plans) to
the cytoplasm.
•
The rRNA (ribosomes) bind to the mRNA. This is
the construction site, where we build the protein.
•
The tRNA brings the materials (Amino Acids) to
the construction site (ribosomes).