Name_______________________________________
Lecture Notes Part II: Protein Synthesis
Why transcription
 DNA cannot leave the ____________, it is too dangerous.
 It must use a messenger _____________
 DNA needs its message to be expressed so the cell can perform all of
its jobs (the proteins go on to do the jobs)
Steps of transcription
Step 1: ___________________
1. Initiation is the beginning of transcription.
 It occurs when the enzyme RNA polymerase binds to a region of a gene called
the _________________
 This signals the DNA to unwind so the enzyme can “read” the bases in one of the
DNA strands.
 The enzyme is ready to make a strand of mRNA with a ______________________
sequence of bases.
Step 2: _____________________
Elongation is the addition of nucleotides to the mRNA strand.
Step 3: _______________________
Termination is the ending of transcription. The mRNA strand is complete, and it detaches from DNA.
Processing RNA
These processes (below) modify the mRNA in various ways. Such modifications allow
_________________________________________________________________________________________________
 Splicing removes ______________ (regions that do not code for proteins) from
mRNA. Only ___________ are left.
 Editing changes some of the nucleotides in mRNA. This creates different forms of
the protein.
 Polyadenylation adds a “tail” to the mRNA (consists of a string of As -adenine
bases). The tail protects mRNA from ______________ that might break it down.
The genetic code
The set of rules by which information in DNA is turned into proteins by living cells.
 The genetic code is ___________________ All known living things have the
same genetic code. This shows that all organisms share a common evolutionary history.
 The genetic code is __________________ Each codon codes for just one amino
acid (or start or stop).
 The genetic code is ___________________. Most amino acids are encoded by
more than one codon.
Translation
 ____________________ is the second part of the central dogma of
molecular biology: RNA → Protein.
 It is the process in which the genetic code in mRNA is read to make a
___________________.
Steps of translation
1. After mRNA leaves the nucleus, it moves to a _______________________, which consists of rRNA and proteins.
2. The ribosome reads the sequence of ________________ in mRNA.
3. Molecules of tRNA bring ____________________________ to the ribosome in the correct sequence
4. While bound to mRNA, tRNA gives up its amino acid.
5. _____ form between the amino acids as they are brought one by one to the ribosome, forming a polypeptide chain.
6. The chain of amino acids keeps growing until a _______________________ is reached
Codons and anticodons
Protein formation
 The polypeptide is the protein’s INITIAL structure (it’s ______________ structure)
 Now based on many factors (amino acids it contains, pH, temperature etc,) it will
FOLD up / or combine with other polypeptides to form its FINAL structure.
Protein functions
Antibodies: Fighting ______________________
Contractile Proteins: Movement!
Enzymes: Facilitate biochemical __________________
Hormonal Proteins: Coordinate bodily activity (blood sugar, childbirth)
Structural Proteins: hair, feathers, horns, beaks, _________________, tendons
Storage Proteins: Store _______________________________
Transport Proteins: Ex: hemoglobin transporting ______________________
Regulatory proteins: Decide which _______________ are turned “on” and “off”