Molecular Basis of Inheritance 01 | The DNA
● DNA discovered by Frederick Misher while studying pus cells
● DNA structure is composed of nucleotides (deoxyribonucleic acid)
● Three steps for DNA to produce proteins: replication, transcription, and
translation
● DNA length varies depending on the number of nucleotides or base pairs, and
differs between species (e.g. human DNA is 2.2 meters long)
● DNA structure consists of nucleoside and phosphate group, with two types of
nitrogenous bases: adenine and guanine
● DNA is made up of four nucleotides (adenine, guanine, thymine, cytosine),
which combine to form glycosidic and phosphor ester bonds
● Double-stranded DNA is antiparallel with nucleotides attached via phosphoric
ester bonds
● DNA structure proposed by Watson and Crick based on complementary base
pairing (adenine pairs with thymine, guanine pairs with cytosine), with a
helical, right-handed twist of 3.4 Angstroms per nucleotide and 10 base pairs
per turn
● DNA length for any organism is the total number of nucleotides multiplied by
the distance
Molecular Basis of Inheritance 02 | The Search for
Genetic Material
● DNA packaging in eukaryotes is done with the help of positively charged
histone proteins.
● The negatively charged DNA is attracted to the positively charged histone
proteins, which helps to reduce its length and increase its thickness.
● The first step in DNA packaging is the formation of a histone octamer, which is
a positively charged ball-like structure called histone protein.
● Histone proteins ensure that the wrapped DNA does not undergo unwinding.
● The structure of the nucleosome represents the basic level of DNA packaging
in eukaryotes.
● The experiment by Griffith on Streptococcus pneumoniae and mice tried to
show that DNA can be the genetic material.
, ● Griffith took two strains of pneumonia - one was disease-causing and another
was non-disease causing and injected them into mice.
● Injecting heat-killed S3 strain releases its genetic material, which is then
picked up by the R2 strain bacteria and synthesizes the protein to produce a
capsule around R2, making it behave like S3 and causing the mice to die.
● The experiment was repeated by three different scientists to prove that DNA is
the genetic material, not RNA or protein.
● Hershey and Chase proved that DNA is the genetic material by labeling
bacteriophages with P32 and S35.
● After infecting bacteria, the virus's genetic material enters the bacteria and
settles down at the base of the test tube due to its weight and radioactivity.
● RNA is highly catalytic and unstable and undergoes fast mutation, making it
unsuitable as a genetic material.
● DNA should be able to express itself in the form of mendelian characters,
which are genes, and is chemically made up of DNA.
Molecular Basis of Inheritance 03 | RNA World &
Replication
● DNA replicates semi conservatively
● DNA is double-stranded and helically coiled
● The daughter strand is synthesized antiparallel to the parental strand
following complementary base pairing rules
● E. coli replicates DNA in 20 minutes and divides within 38 minutes
● E. coli was used to replicate DNA in a medium with N15
● Heavy DNA is obtained through centrifugation in caesium chloride
● New daughter strands are synthesized from nitrogen in the medium which is
N14
● Replication is energetically expensive and involves multiple enzymes
● Replication takes place in the cytoplasm of prokaryotes
● Polymerization speed is fast and can lead to errors
● A single error in replication can cause disorders in the human body
● DNA replication requires the unwinding of DNA duplex by the helicase
enzyme
● The origin of replication is identified by specific nucleotide sequences and is
attacked by helicase
● DNA discovered by Frederick Misher while studying pus cells
● DNA structure is composed of nucleotides (deoxyribonucleic acid)
● Three steps for DNA to produce proteins: replication, transcription, and
translation
● DNA length varies depending on the number of nucleotides or base pairs, and
differs between species (e.g. human DNA is 2.2 meters long)
● DNA structure consists of nucleoside and phosphate group, with two types of
nitrogenous bases: adenine and guanine
● DNA is made up of four nucleotides (adenine, guanine, thymine, cytosine),
which combine to form glycosidic and phosphor ester bonds
● Double-stranded DNA is antiparallel with nucleotides attached via phosphoric
ester bonds
● DNA structure proposed by Watson and Crick based on complementary base
pairing (adenine pairs with thymine, guanine pairs with cytosine), with a
helical, right-handed twist of 3.4 Angstroms per nucleotide and 10 base pairs
per turn
● DNA length for any organism is the total number of nucleotides multiplied by
the distance
Molecular Basis of Inheritance 02 | The Search for
Genetic Material
● DNA packaging in eukaryotes is done with the help of positively charged
histone proteins.
● The negatively charged DNA is attracted to the positively charged histone
proteins, which helps to reduce its length and increase its thickness.
● The first step in DNA packaging is the formation of a histone octamer, which is
a positively charged ball-like structure called histone protein.
● Histone proteins ensure that the wrapped DNA does not undergo unwinding.
● The structure of the nucleosome represents the basic level of DNA packaging
in eukaryotes.
● The experiment by Griffith on Streptococcus pneumoniae and mice tried to
show that DNA can be the genetic material.
, ● Griffith took two strains of pneumonia - one was disease-causing and another
was non-disease causing and injected them into mice.
● Injecting heat-killed S3 strain releases its genetic material, which is then
picked up by the R2 strain bacteria and synthesizes the protein to produce a
capsule around R2, making it behave like S3 and causing the mice to die.
● The experiment was repeated by three different scientists to prove that DNA is
the genetic material, not RNA or protein.
● Hershey and Chase proved that DNA is the genetic material by labeling
bacteriophages with P32 and S35.
● After infecting bacteria, the virus's genetic material enters the bacteria and
settles down at the base of the test tube due to its weight and radioactivity.
● RNA is highly catalytic and unstable and undergoes fast mutation, making it
unsuitable as a genetic material.
● DNA should be able to express itself in the form of mendelian characters,
which are genes, and is chemically made up of DNA.
Molecular Basis of Inheritance 03 | RNA World &
Replication
● DNA replicates semi conservatively
● DNA is double-stranded and helically coiled
● The daughter strand is synthesized antiparallel to the parental strand
following complementary base pairing rules
● E. coli replicates DNA in 20 minutes and divides within 38 minutes
● E. coli was used to replicate DNA in a medium with N15
● Heavy DNA is obtained through centrifugation in caesium chloride
● New daughter strands are synthesized from nitrogen in the medium which is
N14
● Replication is energetically expensive and involves multiple enzymes
● Replication takes place in the cytoplasm of prokaryotes
● Polymerization speed is fast and can lead to errors
● A single error in replication can cause disorders in the human body
● DNA replication requires the unwinding of DNA duplex by the helicase
enzyme
● The origin of replication is identified by specific nucleotide sequences and is
attacked by helicase
