1. 12-3 RNA & Protein Synthesis
Fill-in Notes

2. A Molecular Definition of Genes
Genes are coded DNA instructions that control the production of proteins in the cell
DNA
RNA
Proteins
Transcription
Translation
A Molecular Definition of Genes

3. What is RNA? Ribonucleic acid Like DNA (deoxyribonucleic acid) EXCEPT:
1) 5-carbon sugar is ribose
2) Single-stranded
3) Contains URACIL (U) instead of thymine (T)
What is RNA?

4. Types of RNA Messenger RNA (mRNA)
Serves as “messengers” from DNA to the rest of the cell
Ribosomal RNA (rRNA)
Makes up ribosomes, along with protein
Transfer RNA (tRNA)
Transfer amino acids to the ribosome
Types of RNA

5. TRANSCRIPTION is the copying of a sequence of DNA into a complementary sequence of mRNA
Requires enzyme, RNA polymerase
Binds to and separates DNA strands
Uses strand of DNA as template to assemble mRNA
RNA polymerase binds to promoters, sequences of DNA that signal where to begin transcription
Transcription

6. DNA sequence: GTAAGCTC mRNA sequence: CAUUCGAG
How would we transcribe this sequence of DNA into mRNA?
DNA sequence: GTAAGCTC
mRNA sequence: CAUUCGAG

8. DNA of eukaryotic genes contains sequences called introns, which are NOT involved in coding for proteins
Exons are sequences that code for proteins
RNA Editing

9. Things Found in a Cell Amino acid = smallest part of a polypeptide
Polypeptide = a chain of amino acids.
Protein = a complex structure made of polypeptides
Things Found in a Cell

10. The genetic code is responsible for building all the proteins in the body using 20 different amino acids.
mRNA is the genetic code
4 RNA bases: U, A, G, C
Each coded “message” is 3 bases long
How many 3 letter words can you make from the letters A,T,G and C?
4 x 4 x 4 = 64
The Genetic Code

11. Codons Codons are three letter “words” that specify an amino acid
There are 64 possible codons
Example mRNA sequence:
UCGCACGGU
We would read this as:
UCG – CAC – GGU
Corresponding amino acids:
Serine – Histidine – Glycine
Some amino acids are specified by more than one codon, and some codons are “START” and “STOP” signals
Codons

12. 2 different types of amino acid charts…

13. Which amino acid does AUG stand for?
MET = methionine

15. Which amino acid does CUC stand for?
LEU = leucine
Which amino acid does UGA Stand for?
UGA = Stop

16. TRANSLATION is the process of decoding the information from mRNA to produce proteins
mRNA = instructions
Ribosomes join the amino acids together as directed by the tRNA
Starts with codon-AUG
Ends with a stop codon
Translation

17. Step 1
mRNA that has been transcribed from DNA in the nucleus is released to the cytoplasm

18. Step 2 mRNA attaches to the ribosome
As codons move through the ribosomes, tRNA transfers the correct amino acid to the growing polypeptide chain
Step 2

19. tRNA Transfers the correct amino acid to the chain
At one end an amino acid is attached
At the other end there is an anticodon that pairs with the mRNA
Occurs at the ribosome
tRNA

20. Anticodons are complementary to the mRNA sequence
Which anticodon would be on the tRNA that would pair with UCG on the mRNA?
AGC

21. Step 3
Ribosome forms a bond between the amino acids and releases the used tRNA
Protein grows until the STOP codon is reached
Ribosome then releases the protein and the mRNA

22. Genes & Proteins Genes contain instructions for making proteins
Many proteins are enzymes that catalyze and regulate chemical reactions
These proteins can determine an organism’s traits
For example:
Enzymes can determine pigment color of a flower or human blood type
Genes & Proteins

23. Put your answers at the bottom of your notes (they will be returned to you after they are graded)
Open textbook to pg. 303
Quiz Time

24. 1. Which nitrogenous base replaces thymine (T) in RNA. 2
1. Which nitrogenous base replaces thymine (T) in RNA? 2. How many strands are in RNA? 3. How many letters or bases, make up a codon? 4. What gets made during Translation? 5. Which amino acid gets made from the codons U-U-C? Use pg 303 in book.
QUIZ