1. Unit B7 - 8: Cell Biology
(Protein Synthesis)
Authored by Michelle Choma©
Students who have fully met the prescribed learning outcomes
(PLO’s) are able to:
 B7. Demonstrate an understanding of the
process of protein synthesis.
 identify the roles of DNA, mRNA, tRNA,
and ribosomes in the process of
transcription and translation, including
initiation, elongation, and termination.

2. Unit B7 Continued
 determine the sequence of amino acids
coded for by a specific DNA sequence
(genetic code), given a table of mRNA
codons.
 identify the complementary nature of the
mRNA codon and the tRNA anti-codon.

3. B8. Explain how mutations in DNA
affect protein synthesis.
 give examples of two environmental
mutagens that can cause mutations in
humans.
 use examples to explain how mutations in
DNA change the sequence of amino acids in
a polypeptide chain, and as a result may
lead to genetic disorders.

4. Web Sites & Links for Protein
Synthesis
 http://www.coolschool.ca/lor/BI12/unit6/U06L00.htm
(Unit 06)
 ☺Scroll to Lesson 01 – Lesson 04 (‘U06L01 – L04’)
 http://highered.mcgraw-
hill.com/sites/0072421975/student_view0/chapter2
4/
 (Mader’s Student Edition Website Support for Chapter 24;
Animations, quizzes, flashcards, Thinking Scientifically etc.)
 http://sps.k12.ar.us/massengale/pwpt_biology.htm
 Power point presentation on Protein Synthesis
 http://sps.k12.ar.us/massengale/nucleic_acids_.htm
 (Nucleic acids & protein synthesis, animations)

5. Some more….
 http://
www.phschool.com/science/biology_place/index.html
 Check out the ‘The Biology Place’; Click on link to ‘BioCoach’
activities on Transcription & Translation.
 Fabulous Reviews, Animations, Practice & Self-quiz etc.
 http://www.scilinks.org/retrieve.asp
 (Sign up on this site. Great links on protein synthesis: Link
code, cbn-4123)
 http://www.phschool.com/webcodes10/index.cfm?wcp
refix=cbe&wcsuffix=4123&fuseaction=home.gotoWeb
Code&x=11&y=18
 (Great animation on protein synthesis)

6. And some more….
 http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html
 http://www.pbs.org/wgbh/aso/tryit/dna/index.html#
 (Protein Synthesis activity & animation)
 http://nobelprize.org/educational_games/medicine/dna/intro.htm
l (Review & Animations of protein synthesis)
 http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302
 http://www.eurekacityschools.org/ehs/riggsw/Transcription.ppt
(Powerpoint)
 http://learn.genetics.utah.edu/ (Animation)
 Terrific activities. Check out the Genetics Reference Series and
click on link to ‘The Basics and Beyond’. Follow directions for
Transcribing & Translating a Gene.

7. And more!
 http://
www.pbs.org/wgbh/aso/tryit/dna/shockwave
 www.lewport.wnyric.org/jwanamaker/ani
mations/Protein%20Synthesis%20-
%20long.html
 http://www.wisc-
online.com/objects/index_tj.asp?objid=A
P1302

8. And more links
 http://waynesword.palomar.edu/lmexer3.htm
 ☺Check out the many topics & related articles in the ‘Table of
Contents’
 http://www.estrellamountain.edu/faculty/farabee/biobk/BioBook
PROTSYn.html
 http://distance.stcc.edu/BIOL102/Lectures/lesson10/makeprot.
htm
 http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookgl
ossN.html#nucleic acids
 http://workbench.concord.org/web_content/unitV/sickle_cell_wo
rksheet_s.html (a model-based activity to make a sickle-cell
mutation)
 http://workbench.concord.org/web_content/unitV/muta_wksht_s
.html (a model-based activity to make substitution & deletion
mutations)
 http://www.quizmebc.ca/

9. Introduction
 Protein synthesis is the
manufacture/synthesis of proteins.
 Occurs in the nucleus and cytoplasm.
 The genetic codes for specific proteins are
located on the DNA, e.g. codes for keratin,
collagen, Hb, polymerase, amylase, pepsin etc.

10. Introduction Continued
 The triplet genetic codes on DNA are
called codons. This is a sequence of
three DNA bases.
 The site for protein synthesis occurs on
the ribosomes (rRNA and protein) in the
cytoplasm.

11. Protein synthesis:
divided into 2 processes:
(A) Transcription: copying the codons
for a protein from a segment of the
DNA strand to make mRNA (messenger
RNA); requires 2 enzymes (helicase,
RNA polymerase).
Includes steps of initiation, elongation
and termination.

12. Second Process
(B) Translation: translate the sequence
of codons for the protein on the mRNA
to build a protein at the ribosome; tRNA
assists in this process.
Includes steps of initiation, elongation
and termination.

16. B7– Roles of the Molecules
Involved in Protein
Synthesis
(a) DNA
 Contains the information/genetic
code/triplet codes/codons for the
synthesis of proteins, e.g. TCG, ATG,
ATT.
 Provides a template for mRNA to be
produced.

18. Let’s draw this together!!

20. (b) mRNA
 Carries the coded message from the
nucleus to the cytoplasm, e.g. codons
UAA, CGC, AGU
 Sets the order of amino acids for
protein synthesis by the sequence of
codons. (Codon = 3 bases/ nucleotides in
a DNA or RNA sequence which specify a
single amino acid.)

22. (c) Ribosomes
 Provides a site for mRNA and tRNA to
join together by complementary base
pairing.
 Site for protein synthesis (i.e.
translation) where it translates mRNA
and allows amino acids to bond (peptide
bond).

23. Note:
 rRNA & protein make up the small and
large subunits of ribosomes. The small
subunit contains the binding site for
mRNA and the large subunit contains 2
binding sites for tRNA ~ amino acid and
a dehydration synthesis site!

24. Remember this!!??

26. (d) tRNA
 Carries the specific
amino acid to the
ribosome where its
anticodon
complementary
base pairs with the
mRNA codon, e.g.
mRNA codon- UUA;
anticodon- AAU.

30. (e) Amino acids
 These are the monomers of proteins and
are picked up by tRNA in the cytoplasm,
i.e. tRNA~ amino acids.

31. Note:
 mRNA Codon Table (see below) tells what 3
bases on mRNA code for each amino acid (64
combinations of 3 bases)
 Methionine (AUG) on mRNA is called the
‘START codon’ because it triggers the linking
of amino acids
 UAA, UGA, & UAG on mRNA signal
ribosomes to stop linking amino acids
together

33. mRNA tRNA Amino
DNA
Codon Anticodon Acid
Codon
GCU
TAC
AUU
UUU
TCA
UCU
CTT

35. B7– Steps of Protein Synthesis
 Key words: initiation, elongation,
termination, transcription, translation,
elongation, DNA, mRNA, tRNA, ribosome,
amino acid, triplet code/codons,
template, H-bonds, complementary
pairing, RNA polymerase, anticodon,
peptide bond, polypeptides, dehydration
synthesis.

36. Animations
 http://highered.mcgraw-hill.com/sites/0072421975/stude
 http://www.pbs.org/wgbh/aso/tryit/dna/index.html#
 (Protein Synthesis activity & animation)
 http://www.lewport.wnyric.org/jwanamaker/animation
s/Protein%20Synthesis%20-%20long.html
 http://www.wisc-
online.com/objects/index_tj.asp?objid=AP1302
 http://learn.genetics.utah.edu/
 http://www.eurekacityschools.org/ehs/riggsw/Transc
ription.ppt

37. 1. Transcription
(involves steps of initiation, elongation &
termination)
 Location: nucleus
 Product: mRNA
 Requires 2 enzymes: helicase and RNA
polymerase.

42. Here we go…..
(a) DNA containing genetic code for
protein is in triplet codes.
(b) Initiation: RNA polymerase initiates
transcription by locating and binding to
the beginning of a gene/code (i.e. the
promoter region).

43. (c) Elongation: -Helicase unwinds, unzips DNA,
breaks H-bonds and provides a template for
mRNA formation.
 RNA polymerase travels down the template
and complementary base pairs RNA
nucleotides with DNA codons forming a
mRNA,
 e.g. DNA – CAT; mRNA – GUA.
 RNA polymerase joins adjacent
nucleotides to mRNA, forming the S-P-S
backbone.

44. (d) Termination: -RNA polymerase reaches
termination sequence at end of
gene/code and STOPS mRNA synthesis.
RNA polymerase releases the mRNA and
detaches from the DNA.
 mRNA exits nucleus through its pores
and enters the cytoplasm; DNA rejoins.

45. Note:
 mRNA carries a sequence of codons
(linear order of three RNA bases
complementary to DNA triplet code) to
the ribosome…
 One is a “STOP” codon, e.g. UAA, UAG
and UGA and a “START” codon, e.g. AUG
(Methionine).

46. 2. Translation (involves steps of
initiation, elongation and termination)
 Location: cytoplasm at the ribosome
 Product: protein/polypeptide

49. Translation
(a) tRNAs in the cytoplasm attach the correct
amino acid to one end (aided by enzymes).
(b) Initiation: tRNA~methionine binds to small
subunit and this binds to the mRNA. tRNA
anticodon (UAC) complementary pairs with
mRNA “ START” codon (AUG). Large subunit
binds to the small subunit assembling a
ribosome.

50. Translation continued
(c) Elongation: -Another tRNA (i.e.
tRNA~amino acid) with its anticodon
complementary base pairs with mRNA
codon on the ribosome. (It has 2 binding
sites for incoming tRNA~aa)
 Ribosomes move along one codon to
receive the next incoming tRNA~aa.

51.  Amino acid undergoes dehydration
synthesis and forms a peptide bond.
 “Empty” or outgoing tRNA will bond with
another amino acid in the cytoplasm, i.e.
tRNA~aa.

52. (d) Termination: Synthesis of polypeptide
until a “STOP” codon on mRNA (UAA,
UAG, UGA).
Termination of protein synthesis and the
polypeptide chain and mRNA are
released from the ribosome.
Ribosome subunits separate.

53.  Ribosomes can synthesize 5-15 peptide
bonds/sec!
 Most proteins are 100-200 aa long &
takes less than a minute to be
synthesized!

54.  http://nobelprize.org/educational_games/medicin
(click on animation icon)
 http://highered.mcgraw-
hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535:
:535::/sites/dl/free/0072437316/120077/mi
cro06.swf::Protein%20Synthesis (Great
animation)
 http://sps.k12.ar.us/massengale/proteinsynth
esis%20ppt.ppt (Nice power points 1 & 2 on
Transcrip/lation)
 http://sps.k12.ar.us/massengale/protein%20s
ynthesis2%20ppt.ppt

59. B7– Problems Using the “Table
of mRNA codons”
 Use the following table to answer
questions 1 – 7.
 Note: most of the amino acids are coded
with 2, 3 or even 4 different codons. Of
these 64 codons, 61 are used to program
the 20 amino acids. Three of the 64
codons are used as signals to start or
stop the program.

63. Links
 http://learn.genetics.utah.edu/ Visit the
Genetics Reference Series and click on
link to ‘The Basics and Beyond’. Follow
the directions for synthesis of a protein.

64. Ok Let’s Try it Out!
1.) What are the RNA triplet codes for
Lysine? Leucine?
 using the mRNA table, the codons for
Lysine are AAA or AAG.
 using the mRNA table, the codons for
Leucine are CUU, CUC, CUA, CUG, UUA
and UUG.

65.  2.) What is the DNA triplet code for
Tryptophan?
mRNA = UGG (from table)
DNA = ACC.
 3.) What are the mRNA triplet codons
for “STOP”?
using the mRNA table, the codons
are UAA, UAG and UGA.

66. 4.) The anticodon on a tRNA is GCU.
Determine the name of the amino acid
and its triplet codon.
tRNA anticodon GCU would
complementary base pair with mRNA
CGA at the ribosome.
using the table, the amino acid code for
CGA is Arginine.

67. 5.) DNA contains the following genetic
code: TACAAGATT. Determine the
amino acid sequence.
DNA = TAC|AAG|ATT
mRNA = AUG|UUC|UAA
= methionine-phenylalanine-stop
(from table).