UNIT 8 – PART 2: PROTEIN
SYNTHESIS
http://simplebooklet.com/userFiles/a/8/0/4/0/1/58zw61uZJ2
MmlQe1qywGWW/U6ErNaAx.jpg
The summary color on the
following slides is green and the
underlined words are
vocabulary and hyperlinks are in
blue!
THE CENTRAL DOGMA
 The Central Dogma of biology
states that genetic information
within each cell flows from:
 DNA to RNA to Proteins
 With the help of numerous
enzymes, DNA information
is translated into proteins.
https://cm.jefferson.edu/learn/dna_and
_rna_files/central_dogma_of_molecula
r_biochemistry_with_enzymes.jpg
http://www.csun.edu/~cmalone/pdf360/Ch14-1gen%20code.pdf
WHAT ARE GENES?
chromosomes in the nucleus.
 Sections of the DNA strand code for specific information,
called genes.
 These genes code for proteins.
http://www.accessexcellence.org/RC/VL/GG/images/genes.gif
 We know that DNA within cells is contained within
http://www.accessexcellence.org/RC/VL/G
G/images/genes.gif
GENES CONT.
http://www.virtualmedicalcentre.com/uploads/VM
C/TreatmentImages/2437_dna_450_v2.jpg
 Proteins (AKA polypeptides)
are involved in many biological
functions and are made of
strings of amino acids (AA).
 EX fighting diseases
(antibodies) and speeding
up chemical reactions in our
body (enzymes).
 Proteins also make up
several structures in
multicellular organisms like
skin, hair, and muscles in
animals, too.
FROM DNA TO RNA
http://www.biologycorner.com/resources/mRNA-colored.gif

DNA is held within the nucleus
of eukaryotic cells; the message
of DNA is carried in RNA.
 RNA is single stranded, not
double like DNA.
 There are three types of RNA
(mRNA, tRNA, and rRNA).
RNA CONT.
 RNA is composed of nucleotides with:
 sugar called ribose
 a phosphate group
 and 4 nitrogenous bases
 Uracil
 replaces Thymine
 Adenine
 Guanine
 Cytosine
http://i.livescience.com/images/i/000/053/587/i02/dnarna-structure.jpg?1370549225
TRANSCRIPTION
 mRNA (messenger ribonucleic acid)
carries a copy of the “message” to make
proteins at the ribosomes (rRNA) of the
cell.
 mRNA is created in the nucleus in the
process called transcription (or the
process of copying genetic information
from DNA into mRNA).
 Transcription happens in the nucleus.
http://www.tokyo-med.ac.jp/genet/mutation/nort.gif
TRANSCRIPTION CONT.
 If the DNA code reads like this…





ATC-GTA-CGC-AAT-TGC
…Then the mRNA code reads like this…
UAG-CAU-GCG-UUA-ACG
The enzyme RNA polymerase separates two strands of a DNA
double helix and builds a strand of RNA using RNA nucleotides.
Remember, RNA coding:
 DNA: A T C G
 RNA: U A G C
 “I wish I was adenine so I could pair with “U”
 “U a gansta child”
TRANSLATION – STEP 1
(THE RIBOSOME)
 Translation occurs when the cell
uses the genetic information in
mRNA to build proteins.
 The mRNA carries the “code”
(or instructions) to the
ribosome [organelle in the
cell which builds proteins];
 Ribosome is made of
ribosomal RNA (rRNA).
"Protein Synthesis." Science Online. Facts On File,
Inc. Web. 18 Nov. 2013.
TRANSLATION – STEP 2
(CODONS)
 The ribosome reads mRNA three bases at a time.
 Three nitrogen bases (called a codon or a triplet; EX
“AUG”) code for a specific amino acid; amino acids make
up proteins.
 There is only one “start” codon (AUG) that can begin the
process [the amino acid, methionine].
 UAA, UAG and UGA are 3 stop codons and signal the
ribosome that the protein is complete.
"Protein Synthesis." Science Online. Facts On File, Inc. Web.
18 Nov. 2013.
TRANSLATION – STEP 3
(TRANSFER RNA)
 Based on the mRNA code,
transfer RNA(tRNA) carries
amino acids (AA) to the
ribosome.
 tRNA is a single strand
of RNA that loops back
on itself.
 On one end, a three
letter anticodon that
matches the mRNA
 The other end, the AA
"Elongation of Translation." Science Online. Facts On File, Inc. Web.
18 Nov. 2013.
TRANSLATION – STEP 4
(ELONGATION)
 During elongation,
 tRNA adds AA to the A [attachment] site
 peptide bonds link those AAs together
 mRNA slides through the ribosome to complete to the
growing protein until a stop codon is read.
"Messenger RNA Translation." Science Online. Facts On File, Inc. Web. 18
Nov. 2013.
ANIMATED PROTEIN SYNTHESIS
COPY THE FOLLOWING DIAGRAM
 Complete the missing sections [shown with question
marks]. Turn and talk to your neighbor.
DNA
?
mRNA
?
Protein
?
?
KNOWLEDGE CHECK
 The diagram shows a visual of the central dogma; the
process of creating proteins from the DNA code.
DNA
Transcription
Translation
mRNA
Protein
Ribosome
Nucleus
READING AN AMINO ACID CHART
 An AA chart
helps to
translate
codons.
 There are
various types of
charts.
 Practice: GGA
codes for….?
First
Letter
U
C
A
G
Second Letter
U
C
A
G
Third
Letter
phenylalanine
serine
tyrosine
cysteine
U
phenylalanine
serine
tyrosine
cysteine
C
leucine
serine
stop
stop
A
leucine
serine
stop
tryptophan
G
leucine
proline
histidine
arginine
U
leucine
proline
histidine
arginine
C
leucine
proline
glutamine
arginine
A
leucine
proline
glutamine
arginine
G
isoleucine
threonine
asparagine
serine
U
isoleucine
threonine
asparagine
serine
C
isoleucine
threonine
lysine
arginine
A
methionine
threonine
lysine
arginine
G
valine
alanine
aspartate
glycine
U
valine
alanine
aspartate
glycine
C
valine
alanine
glutamate
glycine
A
valine
alanine
glutamate
glycine
G
http://bioephemera.com/wp-content/uploads/2007/03/image003.jpg
"Genetic Code." Science Online. Facts On File, Inc. Web. 19 Nov. 2013.
http://scienceofknowing.files.wordpress.com/2012/12/codonchart.jpg?w=408
http://www.magrinscience.com/wpcontent/uploads/2013/02/codon-chart.png
KNOWLEDGE CHECK
What determines
the sequence of
amino acids in the
protein shown here?
Discuss the role of
the mRNA codon
and tRNA anticodon
in your answer. Turn
and talk to you
neighbor.
http://upload.wikimedia.org/wikipedia/commons/thumb/3/38/Protein_prima
ry_structure.svg/447px-Protein_primary_structure.svg.png
"Transcription and the Genetic Code." Science Online. Facts
On File, Inc. Web. 19 Nov. 2013.
GENE EXPRESSION
 Multicellular organisms need a variety of cell types to
perform specific functions for the organism; therefore,
individual cells differentiate and become specialized in
structure and function.
 Differentiation happens due to selective gene
expression – some genes are turned off, some are
turned on.
 Internal and external environments can influence gene
expression.
 EX hormones, sex
 EX temperature, nutrition
GENE EXPRESSION EXAMPLE
The arctic fox only
has white fur during
the winter months,
they have brown fur
during warmer
temperatures. This
change in fur color is
an example of
controlled gene
expression.
Image