1. Nucleotides:
* Each nucleotide consists of three parts:
* Sugar: A five-carbon sugar (deoxyribose in DNA, ribose in RNA)
* Phosphate group: A negatively charged molecule attached to the sugar
* Nitrogenous base: A molecule with nitrogen atoms that determines the nucleotide's identity
2. Nitrogenous Bases:
* There are four main types of nitrogenous bases:
* Adenine (A)
* Guanine (G)
* Cytosine (C)
* Thymine (T) - present in DNA
* Uracil (U) - present in RNA
3. Base Pairing:
* In DNA, adenine (A) pairs with thymine (T) through two hydrogen bonds.
* Guanine (G) pairs with cytosine (C) through three hydrogen bonds.
* In RNA, adenine (A) pairs with uracil (U) instead of thymine.
4. Arrangement:
* Nucleotides are linked together in a chain, forming a polynucleotide.
* The sugar of one nucleotide bonds to the phosphate group of the next nucleotide, creating a sugar-phosphate backbone.
* The sequence of nitrogenous bases along the backbone constitutes the genetic code.
* DNA is a double helix: two polynucleotide chains twist around each other, with the nitrogenous bases facing inward and pairing according to the base pairing rules.
* RNA is single-stranded: it consists of a single polynucleotide chain.
5. Importance:
* The specific sequence of nucleotides in a DNA molecule determines the order of amino acids in proteins, which carry out various functions in the body.
* RNA plays a crucial role in protein synthesis, transferring the genetic information from DNA to ribosomes where proteins are made.
In summary: The arrangement of nucleotides, specifically the sequence of nitrogenous bases, holds the key to genetic information and determines the characteristics of living organisms.
