Question

Molecular basis of inheritance notes for biology 2th

Answer 1

DNA

(1) DNA is a long polymer of deoxyribonucleotides.

(2) The length of the DNA depends on the number of nucleotide pairs present in it.

(3) Bacteriophage lambda has 48,502 base pairs.

Central dogma of molecular biology 
(1) Crick proposed the Central dogma in molecular biology

(2) It states that the genetic information flows from DNA à RNA à Protein. 

(3) In some viruses like retroviruses, the flow of information is in reverse direction, which is from RNA à DNA à mRNA à Protein.

Structure of polynucleotide chain:

(1) A nucleotide has three components-

(a) A nitrogen base

(b) A pentose sugar (ribose in RNA and deoxyribose in DNA)

(c) A phosphoric acid.

(2) There are two types of nitrogen bases:

(a) Purines (Adenine and Guanine)

(b) Pyrimidines (Cytosine, Uracil and Thymine)

(3) Adenine, Guanine and Cytosine are common in RNA and DNA.

(4) Uracil is present in RNA and in DNA in place of Uracil, Thymine is present.

(5) In RNA, Pentose sugar is ribose and in DNA, it is Deoxyribose.

(6) Based on the nature of pentose sugar, two types of nucleosides are formed - ribonucleoside and deoxyribonucleotides.

(7) Two nucleotides are joined by 3’-5’ Phosphodiester linkage to form dinucleotide.

(8) More than two nucleotides join to form polynucleotide chain.

(9) The two strands of DNA  (called DNA duplex) are antiparallel and complementary, i.i., one in 5’->3’ direction and the other in 3”->5” direction.