DNA, or deoxyribonucleic acid, is the hereditary material that contains genetic instructions for all living organisms and is primarily located in the cell nucleus. Key discoveries in DNA research include its identification as genetic material in 1944 and the elucidation of its double helix structure in 1953. Ongoing research focuses on applications like gene editing and personalized medicine, highlighting the importance of DNA in fields such as forensic science and evolutionary biology.

1. DNA
The hereditary material
By-Sana Shaikh

2. What is DNA ?
1. DNA also known as Deoxyribonucleic acid,
2. It is the blueprint of life.
3. It holds the genetic instructions for all living organisms.
4. DNA is a molecule that contains the genetic code, which
determines an organism's traits.
5. It is located in the cell nucleus (where it is called nuclear DNA),
6. A small amount of DNA can also be found in the mitochondria
(where it is called mitochondrial DNA or mtDNA).

3. Discovery of DNA
1 1869: Friedrich Miescher Isolates Nuclein
Swiss chemist Friedrich Miescher discovered a new substance in the
nucleus of white blood cells, which he called "nuclein." This
substance was later identified as DNA.
2 1944: Avery, MacLeod, and McCarty's Experiment
Oswald Avery, Colin MacLeod, and Maclyn McCarty demonstrated
that DNA is the genetic material responsible for inheritance. This
was a major breakthrough in our understanding of DNA's role in life.
3 1953: Watson and Crick's Double Helix Model
James Watson and Francis Crick, with help from Rosalind Franklin
and Maurice Wilkins, determined the structure of DNA as a double
helix. This discovery was a landmark achievement in science.

4. Chemical structure of DNA
1 Sugar-Phosphate Backbone
DNA is made up of two long strands of nucleotides,
linked together by a sugar-phosphate backbone.
These strands are twisted around each other to
form a double helix. The sugar-phosphate
backbone gives DNA its structural integrity and
flexibility.
Thymidine Adenine
Cytosine

5. 2 Nitrogenous Bases
The nucleotides in DNA are made up of a sugar, a
phosphate group, and a nitrogenous base. The four
nitrogenous bases in DNA are adenine (A), guanine
(G), cytosine (C), and thymine (T).

6. 3 Complementary Base Pairing
The nitrogenous bases on one strand of DNA pair with
the nitrogenous bases on the other strand. Adenine
always pairs with thymine with two hydrogen bonds,
and guanine always pairs with cytosine with three
hydrogen bonds. This base pairing is essential for
DNA replication and the transmission of genetic
information.
4 Double Helix
The two strands of DNA are held together by
hydrogen bonds between the nitrogenous bases.
The two strands twist around each other to form a
double helix, giving DNA its characteristic helical
shape.
A
G C

7. Genetic information in DNA
Genes
DNA is organized into units called
genes, which contain instructions
for building proteins. These proteins
perform a wide range of functions in
the body, from building tissues and
organs to regulating metabolism
and immune responses.
Codons
The sequence of nitrogenous bases
in DNA is read in groups of three
called codons. Each codon codes for
a specific amino acid, which is the
building block of proteins.
Genetic Code
The genetic code is the set of rules
that relates codons to amino acids.
It is nearly universal, meaning that
the same codons code for the same
amino acids in all living organisms.

8. Mutations and genetic disorders
Mutation Description Effect
Point Mutation Change in a single base Can alter the amino
acid sequence of a
protein, leading to a
change in its function
Insertion Addition of one or more
bases
Can shift the reading
frame, altering the
amino acid sequence
and protein function
Deletion Removal of one or more
bases
Similar to insertion, can
shift the reading frame,
leading to a change in
the amino acid
sequence and protein
function

9. Future of DNA research
Gene Editing
CRISPR-Cas9 is a powerful tool that allows scientists to
precisely edit DNA sequences. This technology has the
potential to cure genetic disorders, develop new
treatments for diseases, and improve crop yields.
Personalized Medicine
DNA sequencing is being used to develop personalized
medicine approaches, tailoring treatments to an
individual's genetic makeup. This allows for more
effective and targeted therapies, minimizing side effects
and improving outcomes.
Forensic Science
DNA analysis has become a crucial tool in forensic
science, used for identifying suspects, determining
paternity, and resolving criminal cases.
Evolutionary Biology
DNA sequencing is revolutionizing our understanding of
evolution. It allows us to study the genetic relationships
between different species and trace the history of life on
Earth.

10. DNA Replication
Unwinding
The double helix is unwound by an enzyme called
helicase, which breaks the hydrogen bonds between the
nitrogenous bases.
Base Pairing
Each strand of DNA serves as a template for the synthesis
of a new complementary strand. An enzyme called DNA
polymerase adds nucleotides to the new strand, following
the rules of base pairing: A with T, and G with C.
New Strands
Two identical DNA molecules are formed, each containing one
original strand and one new strand. This process ensures that
each daughter cell receives a complete copy of the genetic
information.
Lagging strand