1. Building Blocks:
* Nucleotides: DNA is made up of repeating units called nucleotides. Each nucleotide has three parts:
* Sugar (deoxyribose): A five-carbon sugar molecule.
* Phosphate group: A negatively charged group.
* Nitrogenous base: This is the key to carrying genetic information. There are four types:
* Adenine (A)
* Guanine (G)
* Cytosine (C)
* Thymine (T)
2. The Double Helix:
* Two strands: DNA exists as two strands that are twisted around each other, forming a double helix.
* Complementary base pairing: The strands are held together by hydrogen bonds between the nitrogenous bases. A always pairs with T, and G always pairs with C. This is known as complementary base pairing.
3. Genes and the Genetic Code:
* Genes: Specific segments of DNA that contain instructions for building proteins.
* Genetic code: The sequence of nucleotides within a gene determines the sequence of amino acids in a protein. Each set of three consecutive nucleotides (a codon) codes for a specific amino acid. This code is universal across almost all living organisms.
4. Chromosomes:
* Long DNA molecules: DNA is organized into long, linear molecules called chromosomes.
* Packaging: To fit within the nucleus of a cell, chromosomes are tightly packaged with proteins called histones.
5. Information Flow:
* Transcription: The information in DNA is copied into a messenger RNA (mRNA) molecule.
* Translation: The mRNA molecule is used to build a protein.
In Summary:
The order of the four nitrogenous bases in DNA sequences is the language of genetic information. This information is translated into proteins, which carry out a wide range of functions in the body.
This intricate organization allows DNA to store, replicate, and transmit the vast amounts of information necessary for life.
