RNA (ribonucleic acid)
–
–
–
–
single stranded nucleotide chain
ribose sugar
G-C and A-U
Uracil instead of Thymine
– Different types:
– mRNA, tRNA, rRNA
Overview of gene expression:
Molecular biology of the gene
• http://highered.mheducation.com/sites/0077
290801/student_view0/chapter12/3d_animati
on_-_molecular_biology_of_the_gene.html
• www.masteringbiology.com
Username nadinebrown567
Password 1conceptualchemistry1
Play the bioflix called protein synthesis
Types of RNA
The three types of RNA are:
o Ribosomal or rRNA: combines with proteins
to make ribosomes.
o Messenger or mRNA: Carries instructions for
protein synthesis from nucleus to ribosomes
in the cytoplasm
oTransfer or tRNA: Carries amino acids to the
ribosome and matches them to the coded
mRNA message.
DNA Only
-Uses Thymine
RNA Only
Both
-Uses Uracil
-Uses A, G, C
-Single stranded
-Cannot leave the
nucleus
-type of
-Can leave the nucleus
nucleic acid
-Uses ribose sugar
-Uses deoxyribose sugar
-stores info
-Acts as blueprint for
protein production
-made of nucleotides
-Works in actual
protein production
-Double stranded
Proteins are large molecules that are made building blocks
called amino acids.
Hundreds of amino acids linked together by peptide bonds
and fold into a specific shape to make up a protein.
There are 20 different types of amino acids.
Different order of amino acids = different protein!
Functions of Proteins
Most structurally & functionally diverse group of biomolecules!
Function - involved in almost EVERYTHING!
1. Metabolism – enzymes: biological catalysts!
2. Structure – hair, skin, nails (keratin, collagen)
3. Transport (cell membrane channels & pumps, hemoglobin –transports oxygen in
blood)
4. Defense (immune system – antibodies)
5. Regulation- hormones (insulin, HGH, cell cycle )
6. Motion - muscle fibers (actin & myosin)
7. Communication – protein receptors in cellmembrane send and receive chemical
signals (nerve cells)
THE CENTRAL DOGMA
Protein synthesis occurs in two major
parts transcription and translation.
1. Transcription: Process in
which DNA serves as a template
to produce complementary mRNA
2. Translation: Process in
which mRNA is used to link amino
acids together to synthesize proteins.
DNA
 mRNA  Protein
transcription
translation
a
a
From gene to protein
nucleus
cytoplasm
transcription
DNA
a
a
translation
mRNA
a
a
a
a
a
a
a
a
a
a
a
protein
a
a
a
a
a
a
a
ribosome
trait
Transcription
• Making mRNA from DNA
• Occurs in the nucleus
– transcribed DNA strand = template strand
– Enzyme is RNA polymerase
5
C
DNA
G
3
build RNA
A
G
T
A T C
T A
G
A G C
A
T
C G T
C
T
3
G C A U C G U
C
G T A G C A
rewinding
A
T
T
A
A
C
T
A G
C T
G
unwinding
RNA polymerase template strand
mRNA
5
A
T
3
5
GENE = region of DNA that codes for a
protein!
• Eukaryotic genes are not continuous
– exons = the real gene
• expressed / coding DNA
– introns = do NOT contain code for
proteins
introns
come out!
• inbetween sequence
intron = noncoding (inbetween) sequence
eukaryotic DNA
exon = coding (expressed) sequence
mRNA Splicing
• Occurs after Transcription
• Introns are removed and exons are spliced
together to make the mature mRNA transcript
intron = noncoding (inbetween) sequence
~10,000 bases
eukaryotic DNA
exon = coding (expressed) sequence
pre-mRNA
primary mRNA
transcript
mature mRNA
transcript
~1,000 bases
spliced mRNA
The code of life
• Code for ALL life!
• Code is redundant
– several codons
for each amino
acid

Start codon


AUG
Stop codons

UGA, UAA, UAG
Part 2: Translation
1. Takes place in the cytoplasm.
2. mRNA finds a ribosome that is floating in the cytoplasm or attached
to the rough ER.
3. Ribosomes are the site of translation.
4. A sequence of three mRNA nucleotides is called a codon.
5. One codon codes for one amino acid.
6. tRNA molecules enter the ribosome carrying the correct amino
acid. The tRNA has an anticodon that matches the codon on the mRNA.
7. Amino acids are linked together to form a protein!
The types of proteins an organism
possesses depend upon the
sequence of nucleotides