DNA, Genes, and Genetic Code: Structure and Function

DNA (Deoxyribonucleic Acid) is a molecule that carries the genetic information of living organisms. It has a double helix structure, formed by two parallel single strands linked together by complementary base pairing.

Structure of DNA:

• Single strand: Each single strand is composed of a chain of nucleotides linked together by a covalent bond between the phosphate group (C5) of one nucleotide and the OH group (C3) of the next nucleotide. The direction of the single strand is 5’P-3’OH.

• Nucleotide: Each nucleotide consists of:

• A deoxyribose sugar molecule (C5H10O4)

• A phosphate group

• One of four nitrogenous bases: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C)

• Double strand: The two single strands of DNA are linked together according to the complementary base pairing rule: A pairs with T with two hydrogen bonds, G pairs with C with three hydrogen bonds. The two strands have opposite directions: one strand has a 5′-3′ direction, while the other has a 3′-5′ direction.

Function of DNA:

DNA plays a central role in storing, preserving, and transmitting genetic information from one generation to the next.

Gene:

A gene is a segment of the DNA molecule that contains enough genetic information to encode a specific product, which can be an mRNA molecule or a polypeptide chain.

Genetic Code:

The genetic code is a system of conventions using three-nucleotide units (codons) on the mRNA molecule to encode amino acids in a polypeptide chain.

In conclusion:

DNA, genes, and the genetic code are fundamental concepts in genetics, playing a crucial role in determining the traits of organisms and transmitting genetic information from one generation to the next.