STRUCTURE OF DNA PART 2
Summary
TLDRThe DNA double helix model, as proposed by Watson and Crick, is a molecular structure consisting of two anti-parallel chains held together by hydrogen bonds between complementary base pairs: adenine with thymine and cytosine with guanine. This arrangement forms a spiral ladder with a uniform distance maintained by the base pairs and a constant ratio of purines to pyrimidines across species. The sugar-phosphate backbone forms the sides of the ladder, while the base pairs create the rungs of the helix, which coils in a right-handed fashion with 10 base pairs per turn, each separated by 34 angstroms and 36 degrees.
Takeaways
- đ The DNA structure is a double helix, a model proposed by Watson and Crick.
- đ DNA consists of two long, parallel chains that run in opposite directions, known as anti-parallel arrangement.
- 𧏠Each DNA strand is composed of a sugar (deoxyribose), phosphate molecules, and nitrogenous bases.
- đ The bases adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G) through hydrogen bonds.
- đŹ The base pairing follows the principle of complementary base pairing, with A=T and G=C ratios being constant within a species.
- đ Chargaff's rules state that the amount of adenine is always equal to thymine, and the amount of guanine equals cytosine.
- đ The sugar-phosphate backbone forms the outside of the DNA structure, with the base pairs in the center.
- đą The DNA molecule is twisted in a right-handed fashion, with a diameter of about 20 angstroms.
- đ Each turn of the DNA helix includes 10 base pairs or 20 nucleotides, with a uniform distance maintained by hydrogen bonds.
- đ The angle between successive nucleotide pairs is 36 degrees, and each turn of the helix is approximately 34 angstroms long.
- đ The presence of hydrogen bonds was first observed by Linus Pauling in 1954, contributing to the stability of the DNA structure.
Q & A
What is the molecular model of DNA that is widely accepted?
-The widely accepted molecular model of DNA is a double helix structure proposed by Watson and Crick.
How are the two strands of DNA in a double helix arranged in relation to each other?
-The two strands of DNA in a double helix are arranged in an anti-parallel manner, with the 3' end of one strand opposite to the 5' end of the other strand.
What is the significance of the anti-parallel arrangement of DNA strands?
-The anti-parallel arrangement allows for the complementary base pairing, where adenine pairs with thymine and cytosine pairs with guanine.
What are the components of a nucleotide in a DNA chain?
-A nucleotide in a DNA chain consists of one pentose sugar (deoxyribose), two phosphate molecules, and three nitrogenous bases (adenine, guanine, cytosine, and thymine).
How do the bases in the two strands of DNA interact with each other?
-The bases in the two strands of DNA interact through weak hydrogen bonds, with adenine bonding to thymine by two hydrogen bonds and guanine to cytosine by three hydrogen bonds.
Who first observed the presence of hydrogen bonds in the DNA structure?
-Linus Pauling first observed the presence of hydrogen bonds in the DNA structure in 1954.
What is the base ratio in a DNA molecule, and how does it vary between species?
-The base ratio in a DNA molecule is such that the amount of adenine is always equal to thymine, and the amount of guanine is always equal to cytosine. This ratio may vary from species to species but remains constant for a given species.
Who discovered the base ratio rule in DNA, and what is it known as?
-Erwin Chargaff discovered the base ratio rule, which is known as Chargaff's rules.
What are the components of the side railing of the DNA ladder?
-The side railing of the DNA ladder is composed of sugar and phosphate molecules that alternate with each other and are held together by strong chemical bonds.
How is the DNA molecule coiled, and what is the diameter between the two strands?
-The DNA molecule is coiled in a right-handed fashion, and the diameter between the two strands of DNA is 20 angstroms.
What are the structural features of a DNA helix turn, and how many base pairs does it accommodate?
-Each turn of the DNA helix includes one major groove and one minor groove, accommodating 10 base pairs or 20 nucleotides.
What is the angle separating two successive nucleotide pairs in a DNA helix, and what is the length of each turn?
-The angle separating two successive nucleotide pairs in a DNA helix is 36 degrees, and the length of each turn is 34 angstroms.
Outlines
đ DNA Double Helix Structure
The paragraph describes the double helix model of DNA, a structure proposed by Watson and Crick. It highlights that DNA consists of two anti-parallel chains that twist around each other, forming a spiral ladder. Each chain is made up of nucleotides containing a pentose sugar (deoxyribose), phosphate groups, and nitrogenous bases. The bases adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C), creating a complementary relationship between the two strands. The weak hydrogen bonds between these base pairs maintain the uniform distance between the strands. The paragraph also mentions the discovery of the base pairing ratio by Chargaff and the structural characteristics of the DNA molecule, including its right-handed coiling, diameter, and the number of base pairs per turn.
Mindmap
Keywords
đĄDouble Helix
đĄNucleotide
đĄAnti-parallel Arrangement
đĄComplementary Base Pairing
đĄHydrogen Bonds
đĄPurines and Pyrimidines
đĄSugar-Phosphate Backbone
đĄMajor and Minor Grooves
đĄNitrogenous Bases
đĄChromatography
đĄDNA Replication
Highlights
The widely accepted molecular model of DNA is a double helix structure.
Watson and Crick proposed the DNA double helix model.
DNA consists of two long, parallel chains of nucleotides.
The two strands of DNA are anti-parallel to each other.
The 3' end of one strand is opposite to the 5' end of the other.
The base pairing follows the rule of adenine with thymine and cytosine with guanine.
The sequence of bases in one strand is dependent on the other, creating complementary strands.
Hydrogen bonds link the base molecules of the two chains.
The presence of hydrogen bonds was first observed by Linus Pauling in 1954.
Adenine is always equal in amount to thymine, and guanine to cytosine.
The base ratio varies from species to species but remains constant within a given species.
Erwin Chargaff discovered the one-to-one ratio of purines to pyrimidines in DNA.
The sugar-phosphate backbone forms the sides of the DNA ladder.
The base pairs are in the center of the DNA molecule, forming the rungs of the twisted ladder.
The two chains of DNA coil in a right-handed fashion.
The diameter between the two strands of DNA is 20 angstroms.
Each turn of the helix includes one major groove and one minor groove.
Each turn of the helix accommodates 10 base pairs or 20 nucleotides.
The angle separating two successive nucleotide pairs is 36 degrees.
The length of each turn of the helix is 34 angstroms.
Transcripts
model of DNA the widely accepted
molecular model of DNA is a double helix
structure proposed by Watson and Crick
according to them DNA is composed of two
long and parallel chains of trans
helical e called around the same axis
like a spiral ladder the two strands are
anti-parallel to each other in a double
helical DNA one chain is inversely
related to the other that is three prime
end of one being opposite to five prime
end of the other this type of
arrangement of double helical DNA is
called anti parallel arrangement there
are thousands of turns in this spiral
the nucleotide in each chain consists of
one pentose sugar deoxyribose two
phosphate molecule three nitrogenous
bases furies adenine and guanine and
pyrimidine cytosine and thymine among
these bases adenine pairs with thymine
and cytosine with guanine
hence the sequence of bases in one Tola
nucleotide chain of DNA molecule is
dependent on the sequence of bases in
the other the two chains are therefore
said to be complementary to each other
the base molecules of the two chains are
linked through weak hydrogen bonds
between one Piron in one strand and
pyrimidine on the opposite strand this
generates uniform distance between two
strands of hellix the presence of these
hydrogen bonds was first of
served by LC Pauling 1954 this
arrangement gives the ladder-like
appearance to the DNA molecule
adenine bonded to thymine by two
hydrogen bonds a double bond T guanine
is bonded to cytosine by three hydrogen
bonds G triple bonds see the amount of
adenine is always equal to Phi mine and
the amount of guanine always equals to
cytosine the base ratio may vary from
species to species but it is constant
for a given species Erin chargaff
discovered that purines a G and
permanence T C exists in one is the one
ratio the side railing of the ladder are
composed of sugar and phosphate
molecules alternating with each other
and held together by strong chemical
bonds the base pairs are in the centre
of the DNA molecule and formed the Rings
the horizontal steps of spirally twisted
ladder the two chains are coiled in a
right-handed fashion the diameter
between the two strands of DNA is 20
angstroms the length of DNA depends upon
the number of nucleotides the two
strands of DNA a coil to form a twisted
ladder the coiling occurs at an angle of
360 degree this coiling leads to the
formation of turns or helices each turn
of hellix includes one major groove and
one minor groove
each turn accommodates 10 base pairs or
20 nucleotides
the angle separating the two successive
nucleotide pairs is
36-degree and the length of a each turn
is 34 angstrom
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