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Protein Synthesis
Essential Question
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How does DNA code for making proteins (protein synthesis) and
how is this process essential to life?
DNA complementary base pairs: ATGC
RNA complementary base pairs: AUGC
Transcribe the following DNA strand to RNA: ATGGCTATCTAA
UACCGAUAGAUU
Transcription- the process of making mRNA from DNA’s
instructions
1. Enzymes unzip the molecule of DNA by breaking what
specific bond? Hydrogen bond
2. Free RNA nucleotides attach to one exposed strand of DNA
3. The sugar-phosphate backbone bonds. This time is uses
_helicase_ instead of deoxy-ribose.
4. The mRNA breaks away as the DNA strands rejoin. The
DNA returns to its original state_
5. mRNA leaves the ____nucleus____ and enters the
_cytoplasm_. It is headed to a _ribosomes_.
- mRNA carries a genetic message (a sequence of
_nucleotides that instruct how to build proteins_)
- amino acids make up the proteins_
- there are only _20_ common amino acids in the world
Codon = a sequence of 3 nitrogenous bases that match with a
specific amino acid
Example: The RNA strand AUGUAAAUU is actually the
following three codons: _AUG__ _UAA__ _AUU_.
The order of the nitrogenous bases in the mRNA determines the
type and order of the amino acids in a protein.
There are _64_ possible codons but only _20_ Possible Amino
Acids
Stop codons = _UAA UAG UGA
Start codon = _AUG (Methionine or Met)_
More than one codon can code for the same amino acid BUT for
any one codon, there can only by one amino acid!!!
The genetic code is _universal_. (i.e. all organisms use this code
and follow it to make proteins)
Translation = the process of making proteins from amino acids
using the instructions written on mRNA
Translation happens in the _cytoplasm_ at the _ribosomes_.
1. The strand of mRNA attaches to the ribosome_.
2. A tRNA_ molecule brings the first amino acid to the
mRNA strand that is attached to the ribosome.
3. A tRNA _anticodon_ pairs with the first mRNA codon
temporarily. What is the first mRNA codon? _AUG_
Anticodon = region if tRNA that is complementary (or
reverse) to the codon of the mRNA. This is where attaches.
4. _AUG_ signals the start of protein production.
5. The __ribosome__ slides along the mRNA to the next
_codon_.
6. A new _tRNA_ carrying an _amino_ _acid_ pairs with the
second mRNA codon.
7. The first and second amino bond together in a peptide bond.
8. This process continues joining amino acids until the
ribosome reaches a stop codon on the mRNA strand.
9. The amino acid strand (now an amino acid chin ) is released
from the ribosome.
10. Once released the Amino Acid Chain folds into a protein
(tertiary structure!)
Comparison of Replication and Transcription
DNA Replication
DNA Transcription
1. DNA to DNA
2. DNA is permanently split and now has a
parent and daughter strand
3. final product prepares cells for division
but remains in the nucleus (b/c DNA never
leaves)
1. DNA to RNA
2. DNA returns to original state
3. final product shoots out of the nucleus
into the cytoplasm to make proteins at the
ribosomes
Assessment Prompt:
Using the Codon Chart determine the amino acid that matches the given codons below.
ACU- thr.
AUG- met
CCC-pro
TAT- lle
GCA-ala
UGA- stop
GGU- gly
CAT- val