12.3 RNA and Protein Synthesis Notes
 Nevada State Science Content Standard:
L.12.A.2 Students know DNA molecules provide instructions for assembling
protein molecules. E/S
 Objective:
Identify the 3 main types of RNA.
Differentiate between transcription and translation.
 Set: We have talked about the fact that DNA contains genetic material
but as of yet we have not discussed how that material tells an organism
what it should look like or what it should do. Today we will start down
that path.
 Key Vocabulary
Messenger RNARibosomal RNA –
Transfer RNA –
Transcription –
RNA polymerase –
Promoter –
Intron –
Exon –
Codon –
Translation –
Anticodon –
3 main differences between RNA and DNA
1. The sugar in RNA is ribose whereas in DNA it is deoxyribose.
2. RNA is single-stranded.
3. *RNA contains uracil in place of thymine.
3 types of RNA
Message RNA- (mRNA) carries copies of instructions from DNA to the rest of
the cell – blueprint of the genetic code.
Ribosomal RNA – (rRNA) a form of RNA that is a main ingredient in making
ribosomes
Transfer RNA – (tRNA) transfers amino acids to ribosomes for making proteins
*The main job of all RNA, no matter what kind, is protein synthesis.
Transcription – process in which part of the nucleotide sequence of DNA is
copied into a complementary sequence in RNA.
First a strand of DNA is separated into 2 strands then it is copied into RNA.
*RNA is made inside the nucleus during transcription.
RNA polymerase – an enzyme that binds to DNA and separates the DNA strands
during transcription (p 301)
Promotor – a region of DNA that indicates to an enzyme where to bind to make
RNA (p 301)
ANIMATED BIOLOGICAL CONCEPTS DNA Transcription
Intron – intervening sequence of DNA; it does not code for a protein (p 302)
Exon – expressed sequence of DNA; codes for a protein (p 302)
Codon – a 3-nucleotide sequence on messenger RNA that codes fo a single amino
acid (p 302)
*Each codon represents an amino acid.
*Go over the genetic code (P 303) – start from the middle and work out
*The order of nitrogenous bases in DNA determines the order of amino acids in
proteins b/c RNA is a copy of DNA and RNA determines the order of the amino
acids.
*There is no amino acid coded as a stop codon on an mRNA molecule.
Translation – decoding of a mRNA message into a polypeptide chain (protein)
(p 304)
Anticodon – group of 3 bases on a tRNA molecule that are complementary to an
mRNA codon (p304)