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RNA
Ribonucleic Acid
&
Protein Synthesis
8.4, 8.5, 8.7
Protein Synthesis Terms
define these 11 terms for homework
1.
2.
3.
4.
5.
Central dogma
Transcription
Translation
Codon
Anticodon
6. Start codon
7. Stop codon
8. Mutation
9. Point mutation
10. Frameshift mutation
11. mutagens
The Central Dogma of
Molecular Biology
Francis Crick
Information flows in one direction
DNA
Replication
RNA
Transcription
Proteins
Translation
Structure of RNA
3 main differences between RNA and DNA
1. Sugar in RNA is ribose
2. RNA is single stranded
3. RNA contains uracil in place of thymine
Three Types of RNA
Messenger RNA mRNA- carries message
from DNA to ribosome
Ribosomal RNA rRNA- forms part of a
ribosome reads message and assembles
protein at ribosome
Transfer RNA tRNA- brings amino acids
from cytoplasm to ribosome to help make
protein
The Process of Protein Synthesis
Staring
m RNA
r RNA
t RNA
Act 1: Transcription
Act 2: Translation
Transcription
process where a complementary strand
of m RNA is formed from DNA
Scene: The nucleus
Transcription
1. Enzyme (RNA Polymerase) separates DNA strand
2. One strand of DNA used as template to assemble
strand of m RNA.
Translation
Information from DNA is
translated into a protein
Takes place at the ribosome
In the Cytoplasm
Translation- Translating language of
nucleic acids (base sequences) into language of
proteins (amino acids)
1. Gene on DNA carries code to make protein
a. Code written in language with only 4
“letters”, the nitrogen bases A,C,G,U
b. Code read 3 letters at a time, each 3
letter “word” known as a codon
Process uses all 3 types of RNA
a. mRNA from nucleus travels to ribosome
b. rRNA at ribosome reads genetic code from
mRNA , calls for appropriate tRNA
The Genetic Code
consists of 20 amino acids
c. Each tRNA has an anticodon whose bases
are complementary to codon on mRNA. tRNA
brings amino acids to ribosomes
anticodon
codon
d. Ribosome moves along mRNA, binding
new tRNA molecules and amino acids
Mutations
Change in the DNA
May or may not be expressed
Can be beneficial or lethal
Can be spontaneous or caused by
exposure to radiation or toxic chemicals
(mutagens)
Point mutation
one nucleotide is substituted for another
Frameshift Mutation
Changes the way the DNA is read
THE CAT ATE THE RAT
Remove the E
THC ATA TET HER AT
The insertion or deletion of a nucleotide