NOTES: DNA to Protein
There are three types of RNA:
a. Messenger RNA (mRNA) – transfers the genetic
code from DNA in the nucleus to the ribosomes
in the cytoplasm.
b. Transfer RNA (tRNA) – transfers amino acids to
the ribosomes for addition to a protein chain.
c. Ribosomal RNA (rRNA) – makes up part of the
ribosomes for protein synthesis
(“protein synthesis” = making a protein)
How does DNA tell the cell which protein
to make?
A. It uses a nucleic acid called RNA.
B. RNA is a little different than DNA:
1. RNA has the sugar ribose instead of deoxyribose.
2. RNA is only a single strand.
3. RNA contains the nitrogenous base uracil
instead of thymine.
* Uracil bonds with adenine.
Steps in the process of protein synthesis:
Transcription:
1. The helicase… “unzips” part of the double
helix.
Transcription:
2. There is a “start” and “stop” sequence
in the DNA to tell the mRNA where to
start and stop.
UGA = stop
AUG = start
UAA = stop
UAG = stop
Transcription:
3. RNA nucleotides pair up to DNA nitrogenous
bases and…bond in a chain
4. The mRNA travels to the ribosome, where the
protein will be assembled.
(Note: DNA never leaves the nucleus!)
Steps in the process of protein synthesis:
Translation:
5. When mRNA binds to the ribosome,…
production of a protein begins
Steps in the process of protein synthesis:
Translation:
6. The mRNA code is read and converted into
a specific amino acid sequence in a protein
chain
7. This process continues until a functional protein
is made. This means the protein has a purpose,
such as a hormone, enzyme, or a structural part of
a cell membrane.
Summing Up Protein Synthesis
4. A strand of amino acids
make a protein.
3. The tRNA leaves to get
more amino acids.
2. The tRNA brings the
appropriate amino acids to
the mRNA in the ribosome.
1. RNA transcribes the
original DNA strand.