Question

structure of polynucleotide chain explain briefly
about 60 words

Answer 1

Biologists in the 1940s had difficulty in accepting DNA as the genetic material because of the apparent simplicity of its chemistry. DNA was known to be a long polymer composed of only four types of subunits, which resemble one another chemically. Early in the 1950s, DNA was first examined by x-ray diffraction analysis, a technique for determining the three-dimensional atomic structure of a molecule (discussed in Chapter 8). The early x-ray diffraction results indicated that DNA was composed of two strands of the polymer wound into a helix. The observation that DNA was double-stranded was of crucial significance and provided one of the major clues that led to the Watson-Crick structure of DNA. Only when this model was proposed did DNA's potential for replication and information encoding become apparent. In this section we examine the structure of the DNA molecule and explain in general terms how it is able to store hereditary information

Answer 2

ANSWER:-

Polynucleotide chain:-

● A nucleotide has three components:

1. A pentose sugar :-

● Ribose sugar found in RNA is a normal sugar with one oxygen atom attached to each carbon atom.

● Deoxyribose found in DNA is a modified sugar lacking one oxygen atom.

2. Nitrogen base :-

● There are two types of nitrogen bases:

● Purines : Adenine and Guanine.

● Pyrimidines : Cytosine, Thymine and Uracil.

● DNA contains Adenine, Guanine, Thymine and Cytosine.

● RNA contains the same bases except for thymine in whose place uracil is found.

3. A phosphate group :-

Nucleoside :-

● Nucleoside is a product of a pentose sugar and a nitrogen base.

Nucleotide:-

● A nucleotide is formed when a phosphate group is attached to pentose molecule of a nucleoside.

● Number of nucleotides joined together to form polynucleotides.

● A nitrogen base is linked to pentose sugar with N-glycosidic bond.

● Nucleotides are joined with each other by phosphodiester bond.