1. www.psmag.com
FROM DNA TO PROTEINS
PART 3

2. michaelgray.org.uk

3. GENERAL PATHWAY
PROKARYOTES vs EUKARYOTES
employees.csbsju.edu

4. Prokaryotes vs Eukaryotes
Prokaryote Eukaryote
Site of DNA Replication Protoplasm Nucleus
Site of Transcription Protoplasm Nucleus
Site of RNA Splicing Rare Nucleus
Site of Translation Protoplasm Cytoplasm
Site of Recombination Protoplasm Nucleus

5. michaelgray.org.uk
GENERAL STEPS IN DNA REPLICATION

6. DNA REPLICATION
SEMI-CONSERVATIVE

7. STEPS
Unwinding & Strand Separation
Helicase will unwind the parental strands
breaks the H-bonds between bases
SSBP (Single-stranded DNA-binding
proteins)
attaches to separated strands and keep
them from annealing back

8. STEPS

9. Unwinding & STEPS
Strand
Separation
Topoisomerase
breaks and
rejoins the DNA
double helix to
relieve
twisting
forced by the
opening of the
helix
(supercoils) mol-biol4masters.masters.grkraj.org

10. STEPS
Priming
Primase catalyzes synthesis of RNA primers
RNA primers attach to specific site of DNA
strand (ORI region)
Synthesis of New Strands
Leading strand (Continuous): DNA polymerase
III catalyzes synthesis of new DNA strands
at 5’ to 3’ direction (as single polymer) and
extends the leading strand

11. STEPS

12. STEPS
Synthesis of New Strands
Lagging strand (Discontinuous): DNA
polymerase III extends the Okazaki fragments
DNA polymerase I removes RNA primers and
replaces it with DNA
Sealing the nick
DNA Ligase forms covalent bonds from 3’ to 5’
direction to join the Okazaki fragments into a
continuous strand

13. STEPS

14. pulpbits.com
DNA REPLICATION: Prokaryotes

15. DNA REPLICATION: Eukaryotes
For VIDEOS: https://www.youtube.com/
watch?v=27TxKoFU2Nw

16. ENZYMES INVOLVED IN DNA REPLICATION
http://sydney.edu.au

17. TELOMERASE AND GENE
EROSION
TELOMERES: ends of the DNA
each chromosome is one continuous double stranded
length of DNA with 2 telomeres
The 3’ to 5’ parent strand is copied no trouble as the
leading strand BUT the lagging strand (parent 5’ to 3’) has
small primers made every so often and filled in
NOTE: no template at the end to bind to so when the
primers are removed there is an overhang and exposes the
DNA to digestion which would eventually eat into the
genes at the end (gene erosion)

18. TELOMERASE AND GENE EROSION

19. TELOMERASE AND GENE EROSION

20. QUESTIONS????

21. REVERSE TRANSCRIPTION

22. REVERSE TRANSCRIPTION

23. OVERVIEW OF
TRANSCRIPTION
& TRANSLATION

24. TRANSCRIPTION
Process of copying DNA to RNA
NOTE: only one strand of DNA, the template strand,
is used to make mRNA
Does not need a primer to start and can involve multiple
RNA polymerases
Divided into 3 stages
Initiation
Elongation
For VIDEOS: https://
Termination
www.youtube.com/watch?
v=WsofH466lqk

26. STEPS IN TRANSCRIPTION

27. STEPS IN TRANSCRIPTION

28. RNA POLYMERASE
RNA polymerase only transcribes one strand of
the parental DNA molecule (the template strand)
in the 3' to 5' direction
RNA polymerase will never add a T, instead it will
add a U
Transcription ceases when RNA polymerase
encounters special DNA sequences termed
terminators that stop the process of
transcription

29. RECALL…

30. INTRONS AND EXONS
Introns
sequences in the DNA that are NOT used to
make mRNA or to make a protein
they are NOT transcribed
Exons
sequences in the DNA that are expressed or
used to make mRNA and ultimately are used to
make a protein

31. POST-TRANSCRIPTIONAL
MODIFICATION IN EUKARYOTES
RNA SPLICING
REMOVAL OF INTRONS
5’ METHYLATED CAP AND POLYADENYLATION
PREVENTS DEGRADATION DURING TRANSIT
FROM NUCLEUS TO CYTOPLASM

33. FINAL PRODUCT AFTER
TRANSCRIPTION

34. www.can-con.ca
TRANSLATION CAN BEGIN…

35. CONTROL DURING
TRANSCRIPTION
PROKARYOTES
regulating genetic expression in nearby genes
(e.g. LAC OPERON)
EUKARYOTES
involves the organization of chromatin and
specific transcription factors which function by
either changing the rate of transcription or
altering the accessibility of chromatin to
transcriptional machinery

36. the LAC OPERON

37. TRANSLATION:
FROM VAGUE DNA CODES TO
MEANINGFUL TRAITS
blog.lionbridge.com

38. THE ASSEMBLY
barleyworld.org

39. blog.lionbridge.com

40. blog.lionbridge.com

41. blog.lionbridge.com

42. blog.lionbridge.com

43. blog.lionbridge.com

44. For VIDEOS: https://www.youtube.com/watch?
v=5bLEDd-PSTQ

45. IN SUMMARY…

46. EXAMPLE…
DNA
5’-ATG GTT CGG TAG-3’
!
Replicating this strand..
5’-CTA CCG AAC CAT-3’
mRNA transcript to undergo translation
5’-AUG GUU CGG UAG-3’
peptide from mRNA after translation
Met-Val-Arg-STOP

47. THE GENETIC CODE
igoscience.com

48. THE GENETIC CODE
www.mun.ca
http://www.genome.jp/kegg/
catalog/codes1.html

49. NUCLEOTIDE
CODES
A
Adenine
G Guanine
C Cytosine
T Thymine
U Uracil
R Purine (A or G)
Y Pyrimidine (C or T)
N Any nucleotide
W Weak (A or T)
S Strong (G or C)
M Amino (A or C)
K Keto (G or T)
B Not A (G or C or T)
H Not G (A or C or T)
D Not C (A or G or T)
V Not T (A or G or C)

50. AMINO
ACID CODES
Ala A Alanine
Arg R Arginine
Asn N Asparagine
Asp D Aspartic acid
Cys C Cysteine
Gln Q Glutamine
Glu E Glutamic acid
Gly G Glycine
His H Histidine
Ile I Isoleucine
Leu L Leucine

51. AMINO
ACID CODES
Lys K Lysine
Met M Methionine
Phe F Phenylalanine
Pro P Proline
Ser S Serine
Thr T Threonine
Trp W Tryptophan
Tyr Y Tyrosine
Val V Valine
Asx B Asn or Asp
Glx Z Gln or Glu
Xle J Leu or Ile
Sec U Selenocysteine (UGA)
Pyl O Pyrrolysine (UAG)
Unk X Unknown

52. DNA SEQUENCE

53. PROTEIN SEQUENCE
www.wiley.com

54. LET’S TRY…
www.wiley.com
Met M Methionine
His H Histidine
Gly G Glycine
Asn N Asparagine
Leu L Leucine

55. AMINO ACID SEQUENCE
IS…
www.wiley.com
Met M Methionine
His H Histidine
Gly G Glycine
Asn N Asparagine
Leu L Leucine
MHGNL
met-his-gly-asn-leu

56. NUCLEOTIDE SEQUENCE
IS…
www.wiley.com
from the sequence…
(AUA or AUG)-(CAU or
CAC)-(GGU or GGC or
GGA or GGG)-(AAU or
AAC)-(CUU or CUC or
CUA or CUG)
!
EXAMPLE: nucleotide
sequence may be
AUA-CAU-GGU-AAU-CUU
!
EXAMPLE: amino acid
sequence is
MHGNL or met-his-gly-asn-leu

57. LET’S HAVE A GROUPIE…

58. FORM YOUR GROUPS
You will be given set of questions and can discuss by group
for the FINAL answer
The score of the group will be the score of each individual
for today’s QUIZ
Submission is TOMORROW, 12noon, DB (Look for ate Malou)
READY???

59. QUESTIONS
In order to properly construct a protein, which process must
occur first: transcription or translation? Why?
LAC operon: Under what conditions is the operator activated?
Under what conditions is it inactivated?
Assume that the following sequence of bases represents a
segment of DNA that is to undergo transcription. Determine the
corresponding sequence of bases in the resulting RNA molecule.
3’-TAC GGC ATT GCA CAT TTT AGG GGC AAT ATT-5’
The following mRNA segment represents three codons. In each
case determine what the anticodon would be on the appropriate
tRNA.
AAA CGA AAU

60. SEE YOU ON MONDAY FOR
YOUR EXAM 1