1. Transcription
Part of the message encoded within the sequence of bases in DNA must be transcribed into a sequence of bases in RNA before translation can occur
mRNA, tRNA, and rRNA all must be transcribed
Occurs in the nucleus
An enzyme called RNA polymerase separates a section of the DNA molecule and adds complementary base pairs to one strand of the DNA molecule forming an RNA strand.
The new RNA single strand peels off and the DNA double strand goes back together as RNA polymerase moves down the DNA molecule.
Remember RNA contains uracil instead of thymine. So if the DNA strand contains an adenine, then uracil will be added to the RNA strand.

2. Transcription

3. Transcription Modifications of mRNA Poly-A tail added G-cap added
Introns = noncoding region are cut out
Exons = coding region are spliced together

4. Translation
The base sequence in DNA determines the base sequence in RNA (transcription), and the RNA sequence determines the amino acid sequence which makes up the protein (translation).
During translation the RNA bases are “read” in groups of 3. 3 bases are called codons and each combination of 3 bases codes for a specific amino acid.
Some amino acids are coded for by several different codons, but a specific codon always codes for the same amino acid.
Genetic Code p92

5. Translation Types of RNA
mRNA (messenger RNA)- messenger, contains the codons that are translated into an amino acid sequence by the ribosomes
tRNA (transfer RNA)- interpreter, contains an anticodon which is complementary to the codon in mRNA. Also carries the corresponding amino acid which is added to the polypeptide chain (protein)
rRNA (ribosomal RNA)- coordinator, makes up the ribosomes along with proteins. Ribosomes can be free-floating in the nucleus or embedded in the RER. They coordinate the process of translation.

6. Translation
Initiation – the two subunits of the ribosome come together and the first codon that is read is always AUG. It is called the start codon and it codes for the amino acid, methionine.
Elongation – as the ribosome moves along the mRNA, each codon matches an anticodon in a new tRNA, and the tRNA brings the corresponding amino acid and adds that to the chain.
Termination – the stop codons are UAA, UAG, and UGA. When one of these is read the subunits of the ribosome break apart and the polypeptide is released.