1. The document discusses the identification of DNA as the genetic material through a series of experiments in the early 20th century. It describes experiments by Griffith, Avery, Macleod, and McCarty that helped identify DNA as the transforming principle. 2. The definitive experiment was conducted by Hershey and Chase in 1952, where they found that only bacteriophage DNA entered bacteria and was used to produce more bacteriophage, proving that DNA is the genetic material. 3. The document also discusses the structure of DNA as being a double helix with two anti-parallel strands bound together by complementary base pairing between adenine and thymine and cytosine and guanine.

1. Marwan Alhalabi
Professor of Reproductive Medicine and Infertility,
Damascus University
Head of Assisted Reproduction Unit, Orient Hospital
President of Middle East FertilitySociety
President of Syrian Society of Obstetricians and
Gynecologists

2. • The progeny of organism develops characters similar to that
organism
• The resemblance of offspring to their parents depends on
the precise transmission of principle component from one
generation to the next
• That component is-
The Genetic Material

3. The genetic material of a
cell or an organism refers to
those materials found in
the nucleus, mitochondria
and cytoplasm, which play
a fundamental role in
determining the structure
and nature of cell
substances,and capable of
self-propagating and
variation.

4. DNA
Protein
RNA
Protein,RNA and
DNA were thought
as genetic material.
But many
experiments
suggest DNA as
genetic material
rather than protein
and RNA

5. • Must carry information
– Cracking the genetic code
• Must self replicate
– DNA replication
• Must allow for
informationto change
– Mutation
• Must govern the
expressionof the
phenotype
– Gene function

6. RNA PROTEIN
DNA

7. • The process of identification of genetic material began in
1928 with experiments of Griffith and concluded in 1952
with the studies of Hershey and Chase.
• Between these two experiments other three scientists,
Avery, Macloed and McCarty were did an experiment to
identify the genetic material.

8. • 1952 Alfred Hershey and
Martha Chase
• New York scientists
• Performed an experiment that
settled the controversy
• Proved that DNA carries the
genetic material

9. • Bacteriophage: a virus that
infects bacteria.
• When Bacteriophages infect
bacterial cells they produce
more viruses.
• The viruses are released
when the bacterial cells
rupture.

10. • How does the bacteriophage
reprogram the bacterial cell
to make more viruses?
• Does the bacteriophage
DNA, the protein, or both
give instructions to the
bacteria?

11. • Bacteriophage DNA was labeled with radioactive phosphorus
(32P)
• Bacteriophage protein was labeled with radioactive sulphur
(35S)
• only the bacteriophage DNA (as indicated by the 32P) entered
the bacteria and was used to produce more bacteriophage
• Conclusion: DNA is the genetic material

12. • The final evidence that DNA transmits genetic information
was provided by Hershey and Chase in 1952
• They experimented with T2 bacteriophages, viruses that
attack bacteria.

16. • 1928
• Fredrick Griffith
• Bacteriologist
• Trying to prepare a
vaccine against
pneumonia

27. • Two types, or strains, of S. pneumoniae
• First strain is enclosed in a capsule composed of
polysaccharides.
• Capsule protects the bacterium from the body ’ s
defense system.
• Forms smooth-edges (S) when grown in a petri dish
• Helps make the microorganism virulent, or able to
cause disease.

28. • Second strain lacks the polysaccharide capsule
and does not cause disease.
• Forms rough-edges (R) when grown in a petri dish

29. • The harmless R bacteria had changed and
became virulent S bacteria.
• Transformation is a change in genotype
caused when cells take up foreign material.

30. • Based on these observations he concluded that some of
the cells of type II R had changed into type III S due to
influence of dead type III S cells
• He called this phenomenon as transformation
• Principle Componentof type III S cells which induced
the conversionof type II R cells into type III S was
named transforming principle.

31. The Structure of DNA

43. • Double Helix
• Nucleotide
• Deoxyribose
• Base-pairing Rules
• Complementary Base
Pair

44. • 1953—James Watson and Francis Crick
determined the structure of the DNA
molecule to be a
twisted around
double helix
• 2 strands of nucleotides
each other

46. • They proposed that DNA
as a right handed double
helix with two poly
nucleotide chains are
coiled about one another
in a spiral.

48. • Rosalind Franklin contributed
to this discovery by producing
an X-ray crystallographic
picture of DNA
• Determined helix was a uniform diameter and composed
of 2 strands of stacked nucleotides
DNA = tightly wound helix

50. • Nucleotides are the monomeric units that
make up DNA
 3 main parts:
5 carbon sugar—deoxyribose
Phosphategroup
Nitrogenous base

51. Nitrogenous bases
Pyrimidines: single-ring structures
Thymine(T)
Cytosine(C)
Purines: larger, double-ring structures
Adenine(A)
Guanine (G)

54. • Generate and store energy in ATP form
(eukaryote cells).
• Have DNA and mtDNA is double
stranded circular molecule.
• Circular mtDNA has 37 genes. 1 part (D-
loop) does ’ t contain genes. Why?
Becomes displaced during replication.

56. Notice:
DNA strands run in opposite directions =
ANTI-PARALLEL
P
S
S
S
P P
P
S
G
C
A
T

57. Chargaff’s base pairing rule:
Percent of adenine = percent of thymine(A=T)
Percent of cytosine = percent of guanine (C=G)
A+G = T+C (or purines = pyrimidines)

58. Erwin Chargaffshowed the
amounts of the four bases on
DNA ( A,T,C,G)
In a body or somatic cell:
A = 30.3%
T = 30.3%
G = 19.5%
C = 19.9%
T A
G C

59.  Three major forms:
 B-DNA
 A-DNA
 Z-DNA
 B-DNA
is biologically THE MOST COMMON
 It is a helix meaning thatit has a Right handed, or clockwise, spiral.
 Ideal B-DNA has10 base pair per turn
 So each base is twisted 36o relative to adjacentbases.
 Base pair are 0.34 nm apart.
 So completerotation of moleculeis 3.4 nm.
 Axis passes through middleof each basepairs.

61.  Minor Groove is Narrow, Shallow.
 Major Groove is Wide, Deep.
 This structure exists when plenty
of water surrounds molecule and
there is no unusualbase sequence
in DNA-Conditionthatare likely to
be present in the cells.
 B-DNA structure is most stable
configuration for a random
sequence of nucleotides under
physiological condition.

62. A-DNA
 Right-handed helix
 Wider and flatter than B-DNA
 11 bp per turn
 Its bases are tilted away from
main axis of molecule
 Narrow Deep major Groove and
Broad, Shallow minor Groove.
 Observed when less water is
present. i.e.Dehydrating condition.
 A-DNA has been observed in
two context:
• Active site of DNA polymerase
(~3bp)
• Gram (+) bacteria undergoing
sporulation

63. Z-DNA
• A left-handed helix
• Seen in Conditionof High salt concentration.
• In this form sugar-phosphatebackboneszigzag back
• and forth, giving rise to the name Z-DNA (for zigzag).
• 12 base pairs per turn.
• A deep Minor Groove.
• No Discernible Major Groove.
• Part of some active genes form
Z-DNA, suggesting that Z-DNA
may play a role in regulating
gene transcription.

64. Property B-DNA A-DNA Z-DNA
Strand Antiparallel Antiparallel Antiparallel
Type of Helix Right-handed Right-handed Left-handed
Overall shape Long and
narrow
Short and wide Elongated and
narrow
Base pair per turn 10 11 12
Distance between adjacent
bases
0.34 nm 0.23 nm 0.38 nm
Pitch/turn of helix 3.40 nm 2.82 nm 4.56 nm
Helical Diameter 2.0 nm 2.3 nm 1.8 nm
Tilt/inclination of bp to axis 10 200 90

65. Property B-DNA A-DNA Z-DNA
MajorGroove Wide & Deep Narrow & Deep No discrenible
Minor Groove Narrow, shallow Broad, Shallow Narrow, Deep

68. • Two strands wind about each other
in a right-handed manner
• Diameter: ~20Å
• Bases per turn: 10 (~34Å)
• A major and a minor groove
20Å
Major
Minor

69. • One strand of DNA
goes from 5’ to 3’
(sugars)
• The other strand is
opposite in direction
going 3’ to 5’ (sugars)

70. • DNA is wrapped around
abundant nuclear
proteins called Histones
• This formsa complex
called a Nucleosome
• Histones are H1, H2A,
H2B, H3, H4