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The Nucleus and the nucleic acid
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Control region
(leader sequence) |
Central coding region |
Control region
(trailer) |
The cell is the basic unit of life.
The nucleus:
The nucleus is a membrane-bound organelle and is enclosed into a
double membrane that keeps and separates its content from the
cellular cytoplasm. It is present in almost all eukaryotic cells
and contains most of the cell's genetic material in the form of
chromosomes. Nuclear pores regulate the movement of different
molecules is not and outside the nucleus.
The nucleolus, is a prominent
structure within the nucleus. It is mainly involved in
production of ribosomes. Ribosomes are exported to a cytoplasmic
structure known as the endoplasmic reticulum where mRNA is
translated into protein.
Nucleic acid is the genetic material of all known
organisms: the DNA and the
RNA.
Nucleic acids are polymers of nucleotides (generally four types)
that bind together in a chain that may be of millions units
long.
Each nucleotide is composed of:
1. Nitrogenous bases that are of two
types:
• Pyrimidines: include cytosine C, thymine T (in DNA only) and uracil U
(in RNA only).
• Purines: include adenine A and guanine G. They are found in both DNA and
RNA.
2. Pentose sugar (five carbon sugar):
• Deoxyribose in DNA.
• Ribose in RNA.
3. Phosphate group:
The phosphate group binds to pentose sugar by a phosphodiester bond in
which the 5` position of one
pentose
ring bind to the 3` position of the next pentose ring.
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