Transcript PROTEIN SYNTHESIS - Gull Lake Community Schools / Overview

GENE EXPRESSION 13.3
(protein synthesis)
Defn.: the process by which an
organism’s genotype (genetic
makeup) is translated into its
phenotype (physical appearance).
Genes  Traits
Proteins are made up of a particular sequence
of amino acids.
Genes code for the sequence of amino acids
that make up proteins.
Think of DNA as being a “blueprint” or recipe for
making proteins.
DNA works with RNA in making proteins.
STRUCTURAL DIFFERENCES
DNA
RNA
Double-Stranded
Single-Stranded
Sugar: deoxyribose
Sugar: ribose
Base Pairs: T (thymine)
Base Pairs: U (uracil)
Types of RNA
mRNA: complementary to the DNA
sequence of a gene; produced by
transcription.
tRNA: translates (reads) mRNA sequence
into a specific sequence of amino acids;
occurs during translation; has amino acids
attached to it.
rRNA: found in ribosomes (remember that
ribosomes are organelles that make
proteins).
2 Stages of Protein Synthesis
(in order)
Transcription: Genetic information from a
strand of DNA is copied into a strand of
mRNA; “copying notes from the board to
your notebook”.
Translation: process in which the
“language” of nucleic acids (bases) is
changed into the “language” of proteins
(amino acids); mRNA  amino acids 
proteins.
TRANSCRIPTION
RNA polymerase (an enzyme) “unzips” a section
of the DNA strand ….breaks the hydrogen bonds
holding the nitrogenous bases together (the
“steps” of the ladder) at the promoter site.
Unattached RNA (free) nucleotides bind to their
complimentary bases on the DNA strand to form a
molecule of mRNA (messenger RNA); RNA
polymerase works like a “train moving down the
tracks”.
This process repeats until DNA signals to STOP!
The stop signal marks the end of each gene.
mRNA then moves out of the nucleus into the
cytoplasm and attaches to a ribosome  proteins
begin being made.
TRANSLATION
Codon: a 3 base section of mRNA
ex. ATC…__ __ __
* this is how tRNA (transfer RNA) delivers
the amino acids in the correct order.
* codons carry a code for a specific amino
acids.
TRANSLATION (cont.)
Anticodon: a sequence of 3 bases found on
tRNA.
* each tRNA carries only 1 anticodon
which complements a specific mRNA
codon.
* what is the tRNA anticodon for the
mRNA codon GCA?
* what is the tRNA anticodon for the mRNA
codon GCU?
http://users.rcn.com/jkimball.ma.ultranet/Bi
ologyPages/T/Translation.html
http://www.wisconline.com/objects/index_tj.asp?objID=AP
1302