"DNA"The genetic material.

DNA deoxyribonucleic acid.
 DNA is a genetic material.It is a long material about 2 nm thick.It runs continuously within each chromosome.DNA is acidic in nature.






THE CHEMICAL COMPOSITION OF DNA.

DNA is a complex macro molecule.The repeating sub units are called as nucleotides.Each deoxyribonucleotide are made up of
1.A phosphate group.
2.A deoxyribose sugar.
3.A nitrogenous base.

There are\ four different nitrogenous bases.ADENINE (A),GUANINE (G),THYMINE (T),CYTOSINE (C).Adenine and Guanine are larger double ring bases called PURINES..

ADININE

 

 

 Cytosine and Thymine are smaller single ring bases called PYRIMIDINES.

cytosine

 

 All of this four types of nucleotides join to form a polynucleotide chain of DNA molecule.

STRUCTURE OF DNA

JAMES WATSON AND CRICK MODEL.

 In 1953 James watson and Fransis crick gave the model of structure of DNA.They proposed that the DNA molecule is made up of two polynucleotide strand which are twisted around each other in the form of a double helix.The double helix looks like a spiral staircase of uniform diameter.

The railing of this staircase are composed of deoxyribose sugar and phosphate group.

And the steps are made up of nitrogenous bases.Each step consist of purine paired with pyrimidine.Their pairing is highly specific.Adenine pairs with Thymine and two hydrogen bonds are formed between them.While thymine always pairs with thymine and three hydrogen bonds are formed between them.

The two strands of DNA are complementary to each other.I the sequence o bases in one strand is known the sequence of bases in other strand will be automatically known.This property o the two strands of double helix makes DNA a unique molecule best suited to store ,copy.and transmit genetic information from generation to generation.Genetic information is nothing else but the base sequence of DNA in a linear order.

GENES

Genes are short lengths of DNA.

 

Protein are made in special cells under the instruction of genes.Genes sit like a boss sited comfortably on the chromosome in the office the nucleus they get their job done through their manager RNA's.

 

RNA is ribonucleic acid.It is also a polynucleotide but its bases are ribonucleotide.It consist of a phosphate group ribose sugar and nitrogenous bases.Its nitrogenous bases are ADENINE,GUANINE,CYTOSINE and URACIL.DNA controls synthesis of RNA.

Genes express itself in two ways.

1.Transcription

2.Translation.

Copying of DNA encoded information into RNA encoded information is called transcrition.

Translation is decoding of mRNA information into sequence of amino acids in a protein.

The transmission or traits from parents to offspring are called HEREDITY.

The same gene pair are known as alleles.M utation in gene pair my give rise  to many alternate form of genes.They may give rise to changes in phenotype and genotype of an individual.More over DNA also replicates because it is an heredity material.Each free strand is known as template.   

Many diseases are also passed on from generation to generation in genes.Diseases like ANAEMIA,DIABETES,COLOUR-BLINDNESS,HAEMOPHILLIA etc are transmitted from generation to generation.

More in such cases genes can be transplanted with the help of vectors.The most commonly used vector is Plasmid.

  

Transgenic plants and animals are being made by introducing desired foreign gene into them.Some of the common examples areherbicide resistant cotton,soyabean,potatoes,Transgenic animals are normally designed to improve meat yield. Common examples are sheep,goat,and cow.