The discovery of the DNA double helix structure in 1953 by James Watson and Francis Crick was one of the greatest scientific achievements of the 20th century. They were able to determine that DNA consists of two strands coiled around each other to form a double helix. Each strand is made up of a backbone of alternating sugar and phosphate groups with nitrogenous bases protruding from the sugars. The bases on one strand form hydrogen bonds with complementary bases on the other strand. Watson and Crick's double helix model explained how DNA could replicate itself and be stable within organisms. Their discovery fundamentally changed our understanding of genetics and laid the foundation for modern molecular biology and genetic engineering.
DNA
history
structure
X-Ray diffraction image of DNA
base pairing principle
base pairs
bonding patterns of DNA
base stacking different conformations of DNA
different forms of DNA
function of DNA
replication
encoding information
mutation/recombination
gene expression
Application of DNA
DNA
history
structure
X-Ray diffraction image of DNA
base pairing principle
base pairs
bonding patterns of DNA
base stacking different conformations of DNA
different forms of DNA
function of DNA
replication
encoding information
mutation/recombination
gene expression
Application of DNA
DNA = deoxyribonucleic acid.
DNA carries the genetic information in the cell – i.e. it carries the instructions for making all the structures and materials the body needs to function.
DNA is capable of self-replication.
Most of the cell’s DNA is carried in the nucleus – a small amount is contained in the mitochondria.
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.
This Presentation is made for S.Y.Bsc. Students. This presentation includes the structure of nucliec acids DNA, RNA and biological significance of nucliec acids.
RNA- A polymer of ribonucleotides, is a single stranded structure. There are three major types of RNA- m RNA,t RNA and r RNA. Besides that there are small nuclear,micro RNAs, small interfering and heterogeneous RNAs. Each of them has a specific structure and performs a specific function.
Nucleic acids are biopolymers, or small biomolecules, essential to all known forms of life. They are composed of nucleotides, which are monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. If the sugar is a compound ribose, the polymer is RNA (ribonucleic acid); if the sugar is derived from ribose as deoxyribose, the polymer is DNA(deoxyribonucleic acid).
DNA = deoxyribonucleic acid.
DNA carries the genetic information in the cell – i.e. it carries the instructions for making all the structures and materials the body needs to function.
DNA is capable of self-replication.
Most of the cell’s DNA is carried in the nucleus – a small amount is contained in the mitochondria.
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.
This Presentation is made for S.Y.Bsc. Students. This presentation includes the structure of nucliec acids DNA, RNA and biological significance of nucliec acids.
RNA- A polymer of ribonucleotides, is a single stranded structure. There are three major types of RNA- m RNA,t RNA and r RNA. Besides that there are small nuclear,micro RNAs, small interfering and heterogeneous RNAs. Each of them has a specific structure and performs a specific function.
Nucleic acids are biopolymers, or small biomolecules, essential to all known forms of life. They are composed of nucleotides, which are monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. If the sugar is a compound ribose, the polymer is RNA (ribonucleic acid); if the sugar is derived from ribose as deoxyribose, the polymer is DNA(deoxyribonucleic acid).
This power point presentation explains double helical structure of DNA as proposed by Watson and Crick (1953).Attempts have also been made to high light the valuable contributions made by Rosalind Franklin and Wilkins. Brief details of different types of DNA have also been included.
The presentation includes about the basic knowledge of Deoxyribonucleic Acid or DNA. It involves the definition, structure, occurence, quantity, chemical composition, stability, variety, types, molecular weight, complementary of base pairs, absorbance, viscosity, ionic interactions, alternative forms and functions of DNA.
El Niño is a naturally occurring event in the equatorial region which causes temporary changes in the world climate.
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Fungal Transformation in yeast and filamentous fungi
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Conclusion
References
Immobilization of enzymes refers to the technique of confining/anchoring the enzymes in or on an inert support for their stability & functional reuse.
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PAGE is a subtype of the gel electrophoresis whereby the normal gel is replaced with polyacrylamide gels use as the support matrix.
widely used and has very much importance.
COMPLETE PROCEDURE & USES are described in the slide.
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This ppt describes about the similarities between reptiles and modern birds.
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Unstable isotopes are called Radioisotopes.
uses of radioisotopes are many which are discussed in this slide.
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Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
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7. TOPICS TO COVER -:
What is DNA?
DNA structure
Scientific thinking before 1953
Watson and Crick’s Contribution.
Different forms of DNA double Helix.
11. Each strand consists of:
1) A Sugar Phosphate Backbone
2) Four Base Chemicals
(Attached in pairs)
Adenine pairs with Thymine
Guanine pairs with Cytosine
12. STRUCTURE
Basic structure of DNA is a sugar-phosphate backbone with 4
variable nitrogenous bases. This structure is called a nucleotide.
P
sugar Nitrogen
base
Phosphate molecule:
HYDROPHILIC 5-carbon sugar:
DEOXYRIBOSE Nitrogen base:
HYDROPHOBIC
BACKBONE BASE
14. Structure
Does DNA fit the requirements of a hereditary material?
REQUIREMENT DNA Component
Has biologically useful information to
make protein
Genetic code: 3 bases code for 1
amino acid(protein)
Must reproduce faithfully and transmit
to offspring
Complementary bases are faithful:
found in germ cells
Must be stable within a living organism Backbone is strong covalent :
hydrogen bonds
Must be capable of incorporating stable
changes
Bases can change through known
mechanisms
15. THE EARLY EFFORTS
• By the early 1900’s it was known that the chromosomes
carry the genetic (hereditary) information
• Chromosomes consist of DNA (deoxyribonucleic acid)
22. Franklin’s Work
TWO FORMS OF DNA
In 1951 Rosalind Franklin discovers the Two Forms of DNA
through her X-ray diffraction images.
A – Dry Form B – Wet Form
24. SOON AFTER WWII THE RACE TO DISCOVER THE “SECRET OF LIFE” WAS ON. SCIENTISTS KNEW
THIS WOULD BE THE DISCOVERY OF THE CENTURY AND WOULD GUARANTEE A NOBEL PRIZE.
26. On Feb. 28, 1953, Francis Crick walked into the Eagle pub in Cambridge,
England, and, as James Watson later recalled, announced that "we had found
the secret of life." Actually, they had. That morning, Watson and Crick had
figured out the structure of deoxyribonucleic acid, DNA. And that
structure — a "double helix" that can "unzip" to make copies of itself —
confirmed suspicions that DNA carries life's hereditary information.
27. Watson and Crick’s Work
• In 1951 James Watson traveled from the United States to
work with Francis Crick at Cambridge University.
• Watson and Crick used the “Model Building” approach.
• They physically built models out of wire, sheet metal, nuts
and bolts to come up with the structure of DNA.
Why did they build models?
“Sometimes the fingers can grasp what the mind cannot”
(Biology the Science of Life)
28. • DNA consists of two chains of nucleotides in a ladder-like
structure which is twisted (Double Helix)
• Used data of M.H.F. Wilkins and Rosalind Franklin, early
50’s
• Wilkins and Franklin studied
the structure of DNA crystals
using X-rays.
• The X pattern suggested
the structure of DNA was a
helix.
29. • Used data of Erwin Chargaff, 1940’s and
early 50's
• Chargaff’s Rule: His data showed that in each
species, the percent of A equals the percent of
T, and the percent of G equals the percent of
C.
• Watson was shown this picture by Wilkins in
early 1953.
From the picture it was possible to calculate:
1) the distance between bases (3.4A)
2) the length of the period (34A)
3) the rise of the helix (36 degrees)
30. • Francis Crick and James
Watson with Maurice Wilkins
received the 1962 Nobel Prize
for discovering the molecular
structure of deoxyribonucleic
acid (DNA).
• Widely regarded as one of the most important discoveries of
the 20th century it has led the way to the mapping and
deciphering of all the genes in the human chromosomes
31. Watson and Crick Model:
• The sides of the ladder are made up of alternating molecules
of phosphate and deoxyribose.
• The bases make up the rungs of the ladder are attracted by a
weak chemical bonds called hydrogen bonds.
• The DNA double helix is anti-parallel, which means that the
5' end of one strand is paired with the 3' end of its
complementary strand (and vice versa).
• 5'--------------->3‘
3'<---------------5'
• Two hydrogen bonds connect T to A; three hydrogen bonds
connect G to C.
32.
33. “Nature”
Watson & Crick quickly published their Scientific Journal called
“Nature” on April 25th 1953
34. The Nobel Prize
• In 1962Watson, Crick & Wilkins won the Nobel Prize for their
discovery of the structure of DNA.
35.
36. A-DNA
• A-DNA is one of the many possible double
helical structures of DNA.
• It is most active along with other forms.
• Helix has left-handed sense, shorter more
compact helical structure.
• It occurs only in dehydrated samples of
DNA, such as those used in
crystallographic experiments.
37. Structure
• A-DNA is fairly similar to B-DNA.
• Slight increase in the number of bp/ rotation (resulting in a
tighter rotation angle), and smaller rise/turn.
• deep major groove and a shallow minor groove.
• Favoured conformation at low water concentrations.
• In a solution with higher salt concentrations or with alcohol
added, the DNA structure may change to an A form, which is
still right-handed, but every 2.3 nm makes a turn and there are 11
base pairs per turn.
38. Function
• A transition from B-DNA to A-DNA occurs during
Transcription.
A-DNA also plays a imp role in some processes that do not
involve RNA.
For Example:
• In sporulating bacteria, there is a protein which can bind
to DNA in the B-conformation & induce a change to the
A-DNA helix
• Also, Long terminal repeats (LTRs) of transposable
elements, these regions often contains purine stretches
which favour the A-DNA conformation.
39. B-DNA
• Most common DNA conformation in
vivo.
• Favoured conformation at high water
concentrations.
• Also known as Watson & Crick model
of DNA.
• First identified in fibre at 92% relative
humidity.
The B-DNA st ructure
40. Structure
• Narrower, more elongated helix than A.
• Wide major groove easily accessible to proteins & Narrow
minor groove.
• Base pairs nearly perpendicular to helix axis
• One spiral is 3.4nm or 34Ǻ.
• Distance between two H-bonds is 0.34nm or 3.4Ǻ.
41. Z-DNA
• Z-DNA is one of the many possible
double helical structures of DNA.
• Helix has left-handed sense.
• It is most active double helical
structure.
• Can be formed in vivo, given proper
sequence and super helical tension, but
function remains obscure.
42. Structure
• Z-DNA is a transient form of DNA.
• Narrower, more elongated helix than A or B.
• Z-DNA was first discovered in 1979,certain proteins bind very
strongly to Z-DNA.
• Z-DNA plays an important biological role in protection against
viral disease.
• One turn spans 4.6 nm, comprising 12 base pairs.
• The DNA molecule with alternating G-C sequences in alcohol
or high salt solution tends to have such structure.
43. Function
• While no definitive biological significance of Z-DNA has been
found, it is commonly believed to provide torsional strain relief
(supercoiling) while DNA transcription occurs.
• Toxic effect of ethidium bromide on ttrypanosoma is caused by
shift of their kinetoplastid DNA to Z-form.
• Scientists have since discovered that certain proteins bind very
strongly to Z-DNA, suggesting that Z-DNA plays an important
biological role in protection against viral disease.
45. The helix axis of A-, B-, and Z-DNA.
Helix sense : Right-handed Right-handed Left-handed
Bp/turn : 11 10 12
Diameter : 23Ǻ 20Ǻ 18Ǻ
Axial rise(nm) : 0.26 0.34 0.45
46. Factors involved for different DNA conformations:
There are at least three factors on which the DNA conformation
depends
1) Ionic or hydration environment
2) DNA sequences.
3) Presence of specific proteins
In a living cell, DNA is a Mixture of A-& B-DNA conformation
with a few regions capable of forming Z-DNA
47. REFERENCE
Molecular Biology & Biotechnology by H. D. Kumar
DNA Technology the awesome skills by I. Edward Alcamo
The Molecular Biology A Structural Approach by C. U. SMITH
Fundamentals of Molecular Biology by Jayanta.K.Pal
Molecular Biology of the Gene by James.D.Watson
Editor's Notes
Many people believe that American biologist James Watson & English physicist Francis Crick discover DNA in the 1950’s.