Download Protein Synthesis Review Guide

Protein Synthesis Review Guide:
Central Dogma of Molecular Biology: DNA  RNA  Protein
DNA
RNA
Double stranded
Vs
Single stranded
Deoxyribose sugar
Vs
Ribose sugar
Thymine
Vs
Uracil (ie – NO T’s in RNA)
Must stay in the nucleus
Vs
Can enter the cytoplasm
Three main VERBS you need to know:
1) REPLICATE: DNA  DNA. Replicate means to make a copy. DNA replicates because cells are
continually growing and dividing. New copies of DNA are needed for those new cells. DNA cannot leave
the nucleus, so replication takes place in the nucleus.
So when we say replicate, we are talking about DNA making another copy of DNA.
Let’s Practice. REPLICATE this strand: ATTACGTAGGCCTAG
____________________
2) TRANSCRIBE: DNA  RNA In transcription, mRNA is made. Remember, DNA is used as the template
to make the RNA, so this has to take place in the nucleus (DNA can’t leave the nucleus!).
RNA is a nucleic acid like DNA, but it is single stranded (smaller – it can get out of the nucleus!) and RNA
does not have Thymine (T). Instead it has U.
Base pair like this: A-U, T-A, G-C, C-G
Let’s practice. TRANSCRIBE this strand: ATTACGTAGGCCTAG
_____________________
What kind of molecule was the template? _______________
What kind of molecule did you make? _______________
Why do we transcribe RNA? RNA is smaller than DNA and can take DNA’s message out to the
cytoplasm so our cells can make proteins and keep us alive!
Messenger RNA or mRNA carries DNA’s message.
Next up, turning this message (mRNA) into PROTEIN!
3) TRANSLATE: RNA  Protein: When you see “translate” – think NEW LANGUAGE. This word should be
your big hint that you are not going to make another nucleic acid. You will translate that nucleic acid
into the language of proteins. Proteins are built using amino acids as building blocks.
During translation the cell uses information from messenger RNA to build proteins.
Remember, RIBOSOMES are the organelles that make proteins. This happens in the cytoplasm.
If you are going to translate nucleic acid into protein you will need a translator. We use the amino
acid chart or wheel to decode the message in the mRNA into amino acids. Here is the chart.
Let’s Practice. TRANSLATE this mRNA strand: AUGGGUAGU
a) Draw a line down through the sequence after every three bases
b) Three bases on the mRNA = 1 amino acid. We call these three bases a CODON.
c) Use the first letter of the codons to determine what row across you need in the table.
d) Use the second letter of the codons to determine what column down you need.
e) Use the third letter of the codon to determine what amino acid is “coded” for by that codon.
f)
Write down the three letter abbreviation of the amino acid and then a dash, then keep
translating. For example, “met-tyr-ser-gly-Stop”
g) If you encounter a Stop codon while translating - Lucky You! You can STOP translating!
That’s it! Those are the verbs you need to know…
Replicate (make another copy of DNA), Transcribe (make RNA), Translate (make a protein)
Let’s Review Key Players:

DNA – carries our genetic code. The sequence of the bases is what makes each of us unique. All organisms have
the same 4 bases (AGTC), just in a different order!

RNA – mRNA carries the message for making proteins out to the ribosomes in the cytoplasm (blueprint of
genetic code), t-RNA’s transfer amino acids to the ribosomes as proteins are made, rRNA’s make up part of the
ribosomes. All RNAs play a role in protein synthesis.

Codon – three base sequence on mRNA that codes for an amino acid

Anti-codon – three base sequence on tRNA’s that pairs to its complementary codon on mRNA

Gene – section of DNA that codes for a protein.
Amino acid
Anti-codon (3 baes on tRNA)
Codon (3 bases on mRNA)
An important note: This whole process, of a gene on your chromosome being transcribed into mRNA and
then translated into a protein, is a VERY regulated process! The body has control measures in place so
that you don’t just make the protein willy-nilly. You only make it when your body requires it. The
process of GENE REGULATION or GENE EXPRESSION can be controlled at many different points and by
many different factors. Some such factors include transcription factors, promoter location on the
mRNA, RNA editing, and ribosomal binding sites during translation.
MUTATIONS: When something goes wrong!
Mutations are a change in the sequence of nucleotide bases.
This can happen during Replication (DNA  DNA) or during Transcription (DNA  RNA).
There are 3 major types of mutations:
1) Point Mutation: A mutation that involves a single nucleotide is called a POINT mutation (it happens
at a single point). Point mutations may affect 1 amino acid, or perhaps it won’t change the amino
acid at all! (Look at the chart and see what that may be the case).
2) Frameshift Mutation: When you insert a base where it doesn’t belong, or delete a base from the
sequence (insertion & deletion) you have messed with a very delicate language that is read in 3
letter words – codons! This has very serious consequences for the protein if all the amino acids
change.
See here: THE FAT CAT ATE THE RAT.
Insertion: ATH EFA TCA TAT ETH ERA T (I just inserted an A before the sentence, but it messed up
every word following the insertion!)
Deletion: HEF ATC ATA TET HER AR (I just removed the first T in THE and the sentence became
nonsense)
Try your own! Write a sentence with only three letter words and then insert or remove a letter and
see what happens.
3) Chromosomal Mutation: These have major effects on the organism as many proteins are affected.
a) Translocation – piece of chromosome breaks off and attaches somewhere else
b) Inversion – broken chromosome is inserted back in, but in reverse direction
c) Duplication – extra copies of genes on the chromosome
d) Deletion – part of the chromosome breaks off and is lost