DNA and RNA structure - 1

Structure of Nucleic acids

DNA and RNA form the genetic material of all living organisms. They store the information in biochemical form.

What is a gene?
 
A gene is a sequence of nucleotides in DNA or RNA that encodes the synthesis of a gene product, either RNA or protein. The genes are expressed by two important process - Transcription of genes from DNA to RNA and then Translation of Genes into Proteins. While DNA makes multiple copies of itself by the process of DNA replication. We will discuss all of them in detail later.
Structure of DNA 

DNA is a double helical structure. J.D. Watson  and F.H.C. Crick proposed the three-dimensional model of physiological DNA in 1953 on the basis of X-ray diffraction studies of DNA obtained by Franklin and Wilkins. They gave the structure of B- DNA. 
The important features of Watson – Crick Model or double helix model of DNA are as follows:
1. The DNA molecule consists of two polynucleotide chains or strands that spirally twisted around each other and coiled around a common axis to form a right-handed double-helix.
2. The two strands are anti-parallel i.e. they run in opposite directions so that the 3′ end of one chain facing the 5′ end of the other.
3. The sugar- phosphate backbone is on the exterior while the nucleotide bases (ATGC) are in the interior.
4. The two strands are held together by hydrogen bonds between the purine and pyrimidine bases of the opposite strands.
5. Adenine (A) always pairs with thymine (T) by two hydrogen bonds and guanine (G) always pairs with cytosine (C) by three hydrogen bonds. This complimentarity is known as the base pairing rule.                                                                                                          Thus, the two stands are complementary to one another.
6. The base sequence along a polynucleotide chain is variable and a specific sequence of bases carries the genetic information.
7. The base composition of DNA obey's Chargaff s rules .
Chargaff's rules state that DNA from any cell of any organisms should have a 1:1 ratio (base Pair Rule) of pyrimidine and purine bases and, more specifically, that the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine. This pattern is found in both strands of the DNA.
8. The diameter of DNA is 20nm or 20 A. Adjacent bases are separated 0.34 nm or by 3.4 A along the axis. The length of a complete turn of helix is 3.4 nm or 34 A i.e. there are 10bp per turn. (B- DNA-Watson rick DNA)
9. The DNA helix has a shallow groove called minor groove (-1,2nm) and a deep groove called major groove (- 2.2nm) across.
DNA—Watson-Crick Model and Biological Importance (With Diagram)

There are various forms of DNA , based on the structural differences. They are as follows -

DNA: Structure, Forms and Functions (With Diagram)

This are the basics about the DNA structure  and types.
We will study about the  RNA structure and types in the next article.

Thank you , I hope you all understood the topic discussed.

For any queries and suggestions please mail me.

Disclaimer - I do not claim any of the data here. I have referred various books and articles and represented here. All this is just to make concepts easy. Only important and precise data has been provided. It is not for commercial purpose. Your valuable suggestions are always welcome.


Comments

Post a Comment

Popular posts from this blog

History of Microbiology 1

Image
We will learn the history of Microbiology today... Let us start with the Pre-Golden Era. Pre-Golden Era-  Period before 1865 Experienced slow accumulation of some facts about bacteria's Theory of Abiogenesis Previously it was considered that living organisms or creatures arise from non-living matter. This belief is referred to as theory of spontaneous generation or Abiogenesis. Frogs, flies and mice were believed to have originated spontaneously from soil, fertile mud , decaying living organisms, etc. Aristotle was in support of this theory of abiogenesis. Virgil and helmont were also in the favor of the same. Discovery of Microscope Robert Bacon was the first who described lens for the first time. Hans and Janssen produced a first microscope of crude type. Gallielo Galleilee had also made a microscope with a focusing device. Fabri gave the name 'Microscope'. Discovery of Microbial Life Robert hooke had observed cells in the cork of a stem...
Read more

Mendel's Experiment and his laws 1

Image
In last Article we understood what is genetics and what are its applications , now let us study Mendelian genetics.i.e. the experiments carried out by Mendel and the laws proposed by him. Gregor Johann Mendel A priest and teacher from Brunn was sent to university of Vienna for higher studies in physics, mathematics and natural sciences. In 1856 he started his experiments on garden peas(Pisum sativum). Unfortunately his work had remained unnoticed for many years till the findings were rediscovered by three scientists independently. They are- 1.Hugo De Vries from England 2.Karl Correns from Germany 3.Erich Tschermak from Austria Based on Mendel's principle Correns postulated three laws which are known as Mendel's laws of inheritance. Before studying Mendel's experiments let us get introduced to some important terms: Character- It is a feature of an organism.Ex. Height, seed colour,etc. Trait- An inherited character and its desirable variant.E...
Read more

Mendel's Experiment and his laws 2

Image
Mendel performed three experiments- 1. Monohybrid cross 2. Dihybrid cross 3. Trihybrid cross We will study two of them first in this article. 1. Monohybrid cross  It is a cross between two pure individuals(Parents) which are homozygous in which inheritance pattern of only one pair of contrasting characters is studied. Procedure of experiment- Step 1-Selection of parents and obtaining pure lines He selected pure tall pea plant as female plant(TT) and pure dwarf pea plant as a male parent(tt). He confirmed that the plants are true breeding by selfing them for three generations. Step 2-Artificial cross of the selected plants to raise F1 generation He then performed artificial cross, collected seeds, sowed them and waited for the results. He had expected that either the offspring's would be of intermediate height or 50% of them will be tall and 50% of them will be dwarf. But amazingly all were tall and dwarfness disappeared. Step 3-Selfing of F1 hybrids to raise...
Read more