This document provides information about genetic control of protein synthesis, cell function, and cell reproduction. It begins with learning objectives about understanding the structure of DNA and RNA in relation to protein synthesis and the mechanisms of gene expression, cell reproduction, and aging. It then provides details on the central dogma of gene expression including transcription and translation. It describes the structure of DNA and RNA and the process of DNA replication, transcription of DNA to mRNA, and translation of mRNA to proteins. The final sections discuss the cell cycle, mitosis, meiosis, and control of the cell cycle.

1. GENETIC CONTROL OF PROTEIN
SYNTHESIS, CELL FUNCTION AND
CELL REPRODUCTION
CELL PHYSIOLOGY

2. LEARNING OBJECTIVES
At the end of the session, students should be able to:
1. determine the basic structure of DNA and RNA and its
relation to protein synthesis,
2. understand the cellular and molecular mechanism of gene
expression, cell reproduction and aging.

3. GENERAL OVERVIEW OF THE
CENTRAL DOGMA OF GENE
EXPRESSION

7. Gene: section of DNA that creates a
specific protein
Approx 30,000 human genes
Proteins are used to build cells and
tissue
Gene expression involves two
processes:
1) Transcription
2) Translation

8. STRUCTURE OF DNA
• Discovered in 1953 by two
scientists:
• James Watson (USA)
• Francis Crick (GBR)
• Known as the double-helix
model.

9. double-helix structure

10. H
H
H
O
CH2
Base
DNA nucleotide
Phosphate
Deoxyribose
H
H
OH
O
CH2
Base
Phosphate
Ribose
5′
OH OH
4′ 1′
3′ 2′
5′
4′ 1′
3′ 2′
O
O
O
P
O–
O
O
P
O–
O
H
H H
H
NUCLEOTIDES OF DNA AND
RNA
RNA nucleotide

12. Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.
Complementary base pairs in DNA

13. NH2
N O
N
O
N O
N
Adenine (A)
Guanine (G)
Thymine (T)
Bases
Backbone
Cytosine (C)
O
H
H
H
H
H
H
O
O
O
O–
P CH2
O–
H
H
H
H
H
H
H
O
O
O
O
P CH2
O–
NH2
N
N
H
N
N
H
H
H
H
H
O
O
O
O
P CH2
O–
NH2
H
N
N
N
H
N
H
H
H
OH
H
H
O
O
O
O
P CH2
O–
Single
nucleotide
Phosphodiester
linkage
Sugar (deoxyribose)
Phosphate
3′
5′
5′
4′ 1′
2′
3′
5′
4′ 1′
2′
3′
5′
4′ 1′
2′
3′
5′
4′ 1′
2′
3′
CH3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

14. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
H
N H
N
N
N
G
NH2
H
P
S
P
S
P
5′ end
3′ end
H NH2
N
N
H
H
H
H
H
O
O
O
O
P CH2
O–
H
H
H
OH
H
H
O
O
O
O
P CH2
O–
H
H
H
H
H
O
O
O
O
P CH2
O–
CH2
H
H
H
H
H
O
O
O
O–
P
O–
T
2 nm
2 hydrogen bonds
between T and A
T
A
G C
T A
P
P
P
P
P
S
S
S
S
S
S
S
S
S
A
C
G
C G
C G
G C
G C
G
C
G C
C
P
P
S
P
P
P
P
P
S
S
S
S
S
P
P
P
P
P
P
P
P
P
P
S
S S
S
S
S
S
S
S
P
S
S
P
P
P
S
S
S
S
P
3′
5′
G
S
3′
5′
S
A
P
P
C
T A
O
N
N
N
N
A
H
H NH2
N
O
H CH3
H
T
H
H
H2N
N
N C
O
3′ end
5′ end
H
H
H
H
O
O
O
O–
P
CH2
O
H
H
H
H
H
H
O
O
O
O–
P
CH2
O
H
H
H
H
O
O
O
O–
P
CH2
O–
H
H
H
H
O
O
O
O–
P
CH2
O
HO
N
O
H
CH3
H
T
O
N
H N
N
N
G
H2N
H
H
H
N
N
N
N A
H
H2N H
3 hydrogen bonds
between T and A

15. Transcription takes place in the nucleus
 1) DNA double helix is broken apart
 2) mRNA nucleotides match up
 3) Finished mRNA detaches, and moves to a ribosome

16. •Transcription is the process by which a molecule of
DNA is copied into a complementary strand of
RNA.
•This is called messenger RNA (mRNA) because it
acts as a messenger between DNA and the
ribosome where protein synthesis is carried out.

18. TYPES OF RNA
MOLECULES
© John Wiley & Sons, Inc.
 Messenger RNAs (mRNAs)—intermediates that carry genetic information
from DNA to the ribosomes.
 Transfer RNAs (tRNAs)—adaptors between amino acids and the codons in
mRNA.
 Ribosomal RNAs (rRNAs)—structural and catalytic components of
ribosomes.

19. TYPES OF RNA
MOLECULES
 Small nuclear RNAs (snRNAs)—structural components of spliceosomes.
 Micro RNAs (miRNAs)—short single-stranded RNAs (20 to 22 bp) that block
expression of complementary mRNAs.
 RNAi is similar to miRNA (RNA interference, double strand RNA, plant) siRNA
(small interference)
 piRNA (Piwi-interacting RNA) is a small non-coding RNA molecules
© John Wiley & Sons, Inc.

20. • RNA polymerization is similar to DNA synthesis
EXCEPT:
1. The precursors are NTPs (not dNTPs).
2. No primer is needed to initiate synthesis.
3. Uracil is inserted instead of thymine.
The Transcription Process: RNA Synthesis

21. Chemical reaction involved in the RNA polymerase catalyzed synthesis of RNA
on a DNA template strand

22. The Transcription Process
• Transcription is divided
into three steps for both
prokaryotes and eukaryotes.
They are:
1. Initiation
2. Elongation
3. Termination.

25. THE TRANSCRIPTION BUBBLE
© John Wiley & Sons, Inc.
Eukaryotes:
--several RNA polymerases
--no direct recognition binding
--transcriptional factors

26. TRANSCRIPTION AND TRANSLATION IN
EUKARYOTES
© John Wiley & Sons, Inc.

27. THE TRANSCRIPTION BUBBLE
© John Wiley & Sons, Inc.
Prokaryotes:
--RNA polymerase binds specific
nucleotide sequences (promoter
regions) plus transcriptional
factors
--Single RNA polymerase
--DNA unwinding (AT regions)

28. TRANSCRIPTION AND TRANSLATION IN
PROKARYOTES
© John Wiley & Sons, Inc.

30. ELONGATION

31. © John Wiley & Sons, Inc.
Rho-independent terminators—do not require 
intrinsic termination)

32. EUKARYOTIC TRANSCRIPTION:
RNA POLYMERASES
A. RNA POLYMERASE I
LOCATED IN THE NUCLEOLUS, TRANSCRIBES THE 3 MAJOR
RIBOSOMAL RNA
B. RNA POLYMERASE II
LOCATED IN THE NUCLEOPLASM, TRANSCRIBE MESSENGER RNA
AND SOME SMALL NUCLEAR RNA
C. RNA POLYMERASE III
LOCATED IN THE NUCLEOPLASM, TRANSCRIBE TRANSFER RNA
AND SOME SMALL NUCLEAR RNA

33. GENERAL
TRANSCRIPTIONAL FACTOR
(GTF)
Also known as basal transcriptional factors, are a class
of protein transcription factors that bind to specific sites (promoter)
on DNA to activate transcription of genetic information from DNA
to messenger RNA.
 TFIIA
 TFIIB
 TFIID
 TFIIE
 TFIIF
 TFIIH

34. The eukaryotic basal
transcription complex

35. TFIID complex
TFIID
TATA-binding protein
TBP-associated protein

36. RNA CHAIN
ELONGATION
© John Wiley & Sons, Inc.

37. THE 3’
POLY(A) TAIL
© John Wiley & Sons, Inc.
RNA Chain termination

38. MODIFICATIONS TO EUKARYOTIC
PRE-MRNAS

39. REMOVAL OF INTRON
SEQUENCES BY RNA
SPLICING
© John Wiley & Sons, Inc.

40.  Codon: Combination of 3
mRNA nucleotides
 Each mRNA codon matches
with 1 of 20 amino acids
 Ribosome reads codons 1 at a
time
 Codon AUG = Methionine
(Start)
 Codon GUU = Valine
 Codons UAA or UAG or UGA
= Stop

41. H
P
O
O
HO
O
O
CH2
NH2
N
NH
N
N
H
OH
P
O
O
HO
O
O
CH2
NH2
N
N
N
N
H
P
O
OH
HO
O
O
CH2
NH2
N
N
N
N
O
Guanine
Adenine
Adenine
Arginine

42.  Defined: process of decoding a mRNA molecule into a polypeptide
chain or protein.
 Step 1: mRNA enters ribosome
 Step 2: Ribosome reads one mRNA codon at a time
 Step 3: tRNA delivers amino acids until a protein is created

43. Transfer
RNA
(tRNA)

44. (a) Ribbon model
3′ end
(acceptor
site)
5′ end
Double helix
Double helix
Anticodon
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Anticodon loop
3’ end carries
amino acid

45. Because the codon and anticodon don’t match, the
wrong amino acid will not be delivered.
This is why the
anticodon is
important!
Now the codon and
anticodon match. This
ensures the proper
amino acid (serine) is
delivered.

46. ANYTHING
ACID
AMINE
Protein Synthesis
C
O
OH
C
N
H
H
H
C
HO H
C
H
O
C
N
H
H
H
C
H H
C
H
O
OH
C
N
H
H
H
C
HO H
Serine
C
H
O
OH
C
N
H
H
H
C
H H
Alanine
H
C
O
OH
C
R
N
H
H
Amino Acid
H2O

47. GAU AUG CCG AGU CCA GGA UCU UGA
tRNA
UAC
tRNA
GGC
tRNA
UCA
tRNA
GGU
tRNA
CCU
tRNA
AGA
Meth
ionin
e
Pro
-
line
Serin
e
Pro-
line
Gly-
cine
Serin
e
Ribosome
Questions to answer:
1) List the amino acids that
will be delivered to this
ribosome.
2) What is the anticodon of each
codon?
3) When finished, how many
amino acids in size is this
protein?

50.  Interphase
 G1 - primary growth
 S - genome replicated
 G2 - secondary growth
 M - mitosis
 C - cytokinesis

51. CHROMOS
OMES
 All eukaryotic cells store genetic information
in chromosomes.
 Most eukaryotes have between 10 and 50
chromosomes in their body cells.
 Human cells have 46 chromosomes.
 23 nearly-identical pairs

53. SALIENT FEATURES OF
DNA REPLICATION
1. Both strand of DNA in each chromosome are replicated.
2. Both entire strand of the DNA helix are replicated from end to end.
3. The primary enzymes for replicating DNA are complex enzymes called DNA
polymerase. RNA primer is needed for elongation.
4. Formation of each new DNA strand occurs simultaneously in hundreds of
segments along each of the tow strands

55. 0.5 µm
Chromosome
duplication
(including DNA
synthesis)
Centromere
Separation
of sister
chromatids
Sister
chromatids
Centrometers
Sister chromatids

57. MITOSIS
•

58. • (1)Prophase
• (2)Metaphase
• (3)Anaphase
• (4)Telophase
•PMAT
Interphase 1 2
3
4
Cytokinesis

59. Prophase
• The chromatin fibers become
more tightly coiled, condensing
into discrete chromosomes
• The nucleoli disappear.
• The mitotic spindle begins to form.
• The centrosomes move away from
each other, apparently propelled
by the lengthening microtubules
between them.
PROPHASE
Early mitotic
spindle
Aster
Centromere
Chromosome, consisting
of two sister chromatids

60. Metaphase
•The chromosomes’ centromeres lie on
the metaphase plate.
• For each chromosome, the
kinetochores of the sister
chromatids are attached to
kinetochore microtubules coming
from opposite poles.
METAPHASE
Spindle
Metaphase
plate
Centrosome at
one spindle pole

61. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Metaphase chromosome
Kinetochore
Kinetochore
microtubules
Centromere
region of
chromosome
Sister Chromatids

62. Microtubules Chromosomes
Sister
chromatids
Aster
Centrosome
Metaphase
plate
Kineto-
chores
Kinetochore
microtubules
0.5 µm
Overlapping
nonkinetochore
microtubules
1 µm
Centrosome

63. Anaphase
•Anaphase begins when the two sister
chromatids of each pair suddenly part.
• The cell elongates as the
nonkinetochore microtubules
lengthen.
• By the end of anaphase, the two ends
of
the cell have equivalent—and
complete—collections of chromosomes.
ANAPHASE
Daughter
chromosomes

64. Telophase
•Nuclear envelopes arise from
the fragments of the parent
cell’s nuclear envelope and
other portions of the
endomembrane system.
• The chromosomes become
less condensed.
• Mitosis, the division of one
nucleus into two genetically
identical nuclei, is now
complete.
TELOPHASE AND CYTOKINESIS
Nucleolus
forming
Cleavage
furrow
Nuclear
envelope
forming

65. Daughter cells
Cleavage furrow
Contractile ring of
microfilaments
Daughter cells
100 µm
1 µm
Vesicles
forming
cell plate
Wall of
patent cell Cell plate New cell wall
(a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (SEM)

66. Cdk / G1
cyclin
Cdk / G2
cyclin (MPF)
G2
S
G1
C
M
G2 / M checkpoint
G1 / S checkpoint
APC
Active
Inactive
Active
Inactive
Inactive
Active
mitosis
cytokinesis
MPF = Mitosis
Promoting Factor
APC = Anaphase
Promoting Complex
• Replication completed
• DNA integrity
Chromosomes attached
at metaphase plate
Spindle checkpoint
• Growth factors
• Nutritional state of cell
• Size of cell

67. MOLECULAR BASIS OF CELL AGING

69. Proliferative
capacity
Number of cell divisions
Finite
Replicative
Life Span
"Mortal"
Infinite
Replicative
Life Span
"Immortal"
EXCEPTIONS
Germ line
Early embryonic cells (stem cells)
Many tumor cells

70. The main factors acting in cell aging process
AGING

71. Mitochondria
Free radical
by-product
intercellular oxidative stress
(increase senescence)

72. CELL CYCLE
REGULATION
PROTEIN REGULATOR
MUTATION(CANCER
SUPRESSOR,
CYCLINS, MAP
KINASE)
Cell malignancy
or cell death

73. Telomeres are…
 Repetitive DNA sequences at
the ends of all human
chromosomes
 They contain thousands of
repeats of the six-nucleotide
sequence, TTAGGG
 In humans there are 46
chromosomes and thus 92
telomeres (one at each end)
CHROMOSOME
TTAGGGTTAGGGTTAGGGTTAGGGTTAGGG
AATCCCAATCCC
5’
3’
TELOMERE