Question

sketch and explain the structure of DNA and various types of RNA?

Answer 1

DNAis double stranded molecule made up of deoxyribose sugar (pentose sugar),phosphate group and nitrogen bases. DNA is the nucleic acid which stores and transfers genetic information necessary for the development of new cells or organisms.
Structure of DNA:X-ray crystallographic studies have shown that DNA is a right handed double helical structure discovered by James Watson and Francis Crick in 1953. DNA  is made of repeated nucleotides. Nucleotides are made up of pentose sugar, phosphate group and nitrogen bases (Adenine, Thymine, Cytosine, Guanine). DNA runs in 5'-3' orientation. These two strands run antiparallel to each other. The double strands of DNA coil upon each other to form a helical staircase.

RNAis single stranded molecule made up of ribose sugar (pentose sugar), phosphate group and nitrogen bases (Adenine, Uracil, Guanine and Cytosine). RNA codes for amino acids. It also acts as a messenger between DNA and ribosomes during the process of photosynthesis.

Structure of RNA:RNA occurs in three forms namely, mRNA, tRNA and rRNA.
mRNAis the messenger RNA is a single stranded RNA made up of 1000 nuclotides which carries genetic code from DNA in the nucleus to the ribosomes, the sites of protein synthesis.
rRNA is a large and complex double helical structures. These are attached to ribosomes during initiation of protein synthesis.
t-RNAare small molecules made up of about 80 nucleotides. tRNA act as carriers of amino acids from the cytoplasm to the sites of protein synthesis, the ribosomes.

Answer 2

Answer:

In 1953 Watson and crick proposed a model of the DNA molecule. According to this model the two threads[strands] of nucleotides coil around each other to form double helix.

This double helical stucture appears as flexible ladder.

Each strand is made up of nucleotide. These nucleotides are the unit of DNA.

A molecule of a nitrogenous base and phosphoric acid are joined to a molecule of sugar to form nucleotide. There are four types of nitrogenous base in the form of adenine and guanine [purines] thymine and cytosine [pyrimidines]. Thus four type of nucleotide are formed.

The adenine always pair up with thymine and guanine always pair up with cytosine.

Three type of RNA.

1. rRNA= ribosomal RNA

2. mRNA= messenger RNA

3. tRNA= transfer RNA

rRNA = It play structural and catalytic roles.

mRNA= It provides the tamplate.

tRNA= It's brings amino acid and reads the code.