1. RNA & PROTEIN SYNTHESIS
THE PROCESS OF MAKING PROTEINS

2. THE STRUCTURE OF RNA Made of long chains of nucleotides Sugar = ribose
Single stranded
Uracil replaces thymine
Major differences of DNA and RNA
The sugar of DNA is called deoxyribose
DNA has thymine not uracil
DNA is a double strand (double helix)

3. 3 TYPES OF RNA
Messenger RNA (mRNA) – carries copies of instructions from the DNA (serve as messengers from the DNA to rest of cell).
Ribosomal RNA (rRNA)– proteins that make up ribosomes.
Transfer RNA (tRNA)– transfers amino acids from mRNA to the ribosome.

4. TRANSCRIPTION
Transcription – RNA molecules are produced by copying part of the nucleotide sequence of DNA into a complementary strand.
RNA polymerase: enzyme that helps unwind and unzip the DNA strand.

5. During transcription:
RNA polymerase binds to DNA
It then separates the strands of the double helix
RNA polymerase uses one strand as a template or model
Nucleotides are assembled into a strand of RNA based on what nucleotides the DNA has.
DNA: AATTGGCC
RNA: UUAACCGG

6. TRANSCRIPTION Section 12-3 RNA polymerase DNA RNA Go to Section:
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA polymerase
DNA
RNA
Go to Section:

7. HOW DOES RNA POLYMERASE KNOW WHEN TO START & STOP
There are certain nucleotide sequences on the DNA that the enzyme will bind to = promoter.
The promoter is the signal so that RNA polymerase knows where to begin on the DNA molecule. Remember how big DNA is.
A similar signal stops transcription.

8. The Genetic code Your body is made mostly of proteins.
Proteins are made when amino acids are joined together in long chains called polypeptides.
Properties of proteins including how they function is determined by the order of amino acids in the polypeptide chain.
The language of mRNA is called the genetic code

9. Interactive: transcribe then translate.
Interactive: compare dna replication and protein synth

10. RNA is made of four bases: A,U,G,C.
The code is written in a language uses just these four letters.
The code is read 3 letters at a time so that each “word” of the coded message is 3 bases long.
Each 3 letter “word” in RNA is called a codon.

11. CODONS
Codon – 3 consecutive nucleotides that specify a single amino acid that is added to a polypeptide chain.
Bases on RNA: UCGCACGGU
Broken in 3’s: UCG-CAC-GGU
Amino acids the bases code for.
Serine – Histidine – Glycine
There are 20 amino acids in all.
Every protein in the world is a different arrangement of these 20 amino acids.
It like the 26 letters of the alphabet can make uncountable words. 20 amino acids makes uncountable numbers of amino acids.

12. 64 POSSIBLE CODONS

13. TRANSLATION
Translation – the cell uses the information from mRNA to make proteins.
Takes place in the ribosomes.
The ribosome reads the message.

14. 1st & 2nd Steps
After transcription of DNA in the nucleus, the mRNA leaves the nucleus, goes through the cytoplasm and to the ribosome.
mRNA attaches to a ribosome.
tRNA brings amino acids to mRNA on the ribosome.
tRNA has a 3 base code that is complimentary to the 3 base code of mRNA.
3 bases on the tRNA = anticodon.
Anticodons match up with codons.
mRNA codon: UUC
tRNA anticodon: AAG

15. tRNA has the anticodon so that it knows what amino acid to bring.
The ribosome will form a peptide bond between the first two amino acids.
Then tRNA goes to get another A.A.
This continues until the polypeptide chain (protein) is finished.
until it reaches a stop codon on the mRNA.
It then releases the polypeptide chain.

16. Translation: mRNA and tRNA
Nucleus
Messenger RNA
Messenger RNA is transcribed in the nucleus.
mRNA
Lysine
Phenylalanine
tRNA
Transfer RNA
The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.
Methionine
Ribosome
mRNA
Start codon
Go to Section:

17. Translation continued: FORMING THE POLYPEPTIDE CHAIN
The Polypeptide “Assembly Line”
The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids.
Growing polypeptide chain
Ribosome
tRNA
Lysine
tRNA
mRNA
Completing the Polypeptide
The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.
mRNA
Translation direction
Ribosome
Go to Section:

18. Bring amino acids to ribosome
Concept Map
RNA
can be
Messenger RNA
Ribosomal RNA
Transfer RNA
also called
which functions to
also called
which functions to
also called
which functions to
mRNA
Carry instructions
rRNA
Combine
with proteins
tRNA
Bring amino acids to ribosome
from to
to make up
DNA
Ribosome
Ribosomes
Go to Section:

20. Proteins Nearly everything in life is made of proteins.
Many proteins are enzymes that act as catalyst for chemical reactions. (they speed up reactions)
Flower colors, pea shape, eye color etc.
Mendel would have been surprised about this.

21. Summary: Protein synthesis takes place in 2 steps:
Transcription and translation
Transcription:
DNA unzips
mRNA is made by complimentary base pairing
Happens in the nucleus.

22. Translation:
mRNA leaves the nucleus and goes to the ribosome.
At the ribosome, a specific protein is made.
This is done by tRNA adding amino acids to a growing chain.

24. GCC:
AUG:
UUU::
ACG:
CGU:
TTT:

25. CCC:
GCA
UUU
AUG
AGG
AAA
CGC
ATG: