1. Nucleotides:
* The building blocks of DNA: These are the individual units that link together to form the long chains of DNA.
* Structure: Each nucleotide consists of three parts:
* A sugar molecule (deoxyribose): This forms the backbone of the DNA strand.
* A phosphate group: This is attached to the sugar and helps link nucleotides together.
* A nitrogenous base: This is the part that carries the genetic information. There are four types of nitrogenous bases in DNA:
* Adenine (A)
* Guanine (G)
* Cytosine (C)
* Thymine (T)
2. Bases and their pairing:
* Adenine (A) always pairs with Thymine (T) through two hydrogen bonds.
* Guanine (G) always pairs with Cytosine (C) through three hydrogen bonds.
* These base pairings are crucial for:
* DNA replication: The base pairings allow DNA to make an exact copy of itself when a cell divides.
* Protein synthesis: The sequence of bases in a DNA molecule determines the sequence of amino acids in a protein, which determines the protein's function.
3. Double Helix:
* The structure of DNA: DNA is a double helix, which means it looks like a twisted ladder.
* The sides of the ladder: The sugar-phosphate backbones of the two DNA strands form the sides of the ladder.
* The rungs of the ladder: The nitrogenous bases from each strand pair up to form the rungs of the ladder.
4. Genes:
* Segments of DNA that code for specific proteins: Genes are like instructions that tell the cell how to make a specific protein.
* Located on chromosomes: Genes are located on chromosomes, which are long strands of DNA organized within the nucleus of a cell.
* Control traits: Genes determine traits like eye color, hair color, and even susceptibility to certain diseases.
In Summary:
DNA is made up of nucleotides, which are linked together to form two long strands. These strands are held together by the pairing of nitrogenous bases (A with T, and G with C). This double helix structure allows DNA to be easily replicated and transcribed into RNA for protein synthesis, which is essential for all life functions.
