BIOLOGY LECTURE ON NUCLEIC ACIDS

 NUCLEIC ACIDS  [DNA &RNA]

There are chromosomes in the nucleus of cell,which are thread like.They are visible only during cell division.Chromosomes are uncoiled in loose network called chromatin contains DNA,RNA,& PROTEINS.

                                

DNA means DEOXYRIBONUCLEIC ACID 

RNA means RIBONUCLEIC ACID.

DNA & RNA both are information storage devices of cell.These are two kinds of nucleic acids.

DNA: It has special coded genetic programme with detailed & specific instructions for each organism heredity.[one gene one character passed to offspring].

Its model was proposed by WATSON & CRICK In 1953.

It consists of linear polymers of repeating monomer subunits called nucleotides.

Each nucleotide contains A PENTOSE SUGAR,A PHOSPHATE GROUP,NITROGENOUS BASE[PURINE or PYRIMIDINE] A ,G ,C,T

SUGAR RIBOSE in RNA

DEOXYRIBOSE In DNA[One oxygen lacking]

DNA is double helicle, two polynucleotide chains held together by weak hydrogen bonds between adjacent bases.

Two chains are oriented in opposite directions & arranged side by side like a ladder. NITROGENOUS Bases form the cross rings of ladder. Coiled spirally entire structure becomes double helix.

A Means ADENINE G Means GUANINE C Means CYTOSINE T Means THYMINE A=T C☰G Double bond between A & T, Triple bond between C & G

It represent the ladder with S-P Backbone representing rails & paired N- BASES as steps.

ADENINE & GUANINE are PURINES have two rings of PHOSPHATE.THYMINE & URACIL are PYRIMIDINES have one ring of PHOSPHATE.[A derivative of phosphoric acid] provides the covalent which connect sugar in series.Alternating P-S-P-S MOLECULES.

DNA plays a key role in transmission of genetic character both from cell to successor & in gene expression. GENE - Its main function is to make its copies transmitted to daughter cells help in maintaining genetic composition. A-T , G-C.One helix give rise to two double daughter helices,replica of original called DNA -REPLICATION.

RNA 

It is a long chain of nucleotide[one stranded]. IN RNA there is URACIL[A PYRIMIDINE] instead of THYMINE. URACIL has one ring of phosphate.This is also informational molecule.

There are three types of RNA :

1. mRNA MESSENGER RNA
2.  tRNA TRANSFER RNA
3.  rRNA RIBOSOMAL RNA

RNA has major role in PROTEIN SYNTHESIS.

 mRNA Gives sequence of different amino acids to be incorporated into PROTEIN.

tRNA Carrier delivers correct amino acid for PROTEIN.

rRNA Major component of RIBOSOME IN PROTEIN SYNTHESIS.         

ATP 

ADENOSINE TRIPHOSPHATE

It is a nucleotide have ADENINE , RIBOSE & 3 PHOSPHATE is energy molecule of cell.It stores & release energy when a bond is broken.

ADENOSINE DIPHOSPHATE changes into TRIPHOSPHATE.