Gene: A gene is the fundamental unit of heredity in biology, consisting of a DNA segment that plays a role in a specific function. Officially, guidelines define a gene as a "DNA segment that contributes to phenotype/function. In cases where a function is not demonstrated, a gene may be identified by its sequence or homology."DNA: Genes are constructed from DNA, a molecule with the distinctive shape of a double helix, similar to a twisted ladder. Each rung of this ladder is made of two paired chemicals known as bases. There are four types of bases: adenine (A), thymine (T), cytosine (C), and guanine (G), each represented by the first letter of its name. Certain bases always pair together: adenine with thymine (A-T) and cytosine with guanine (C-G). Various sequences of these base pairs create coded messages.The Gene: A gene consists of a sequence of bases, combining A, T, C, and G in various ways. These combinations determine a gene's function, much like letters form words. Each individual has thousands of genes, amounting to billions of DNA base pairs or bits of information, repeated in the nuclei of human cells, which define personal traits (genetic characteristics).The Chromosome: Genes are meticulously organized along 23 pairs of larger structures called chromosomes. One chromosome in each pair is inherited from the mother, and the other from the father. Chromosomes within a pair are similar, except in males, where one pair, which determines sex, consists of two X chromosomes in females and one X and one Y in males.The X and Y Chromosomes: These are the sex chromosomes, always denoted with capital letters, X and Y. All other human chromosomes are numbered from 1 to 22 and are referred to as autosomes, meaning "the other chromosomes."History of the Gene: 1869-1970: - 1869: DNA is identified in cells, though its functions remain unknown. - 1909: The term "gene" is introduced, and the chemical structure of DNA is discovered. - 1920: Chromosomes are proposed as carriers of hereditary traits. - 1944: DNA is linked to the inheritance of traits. - 1951: The first clear diffraction images of DNA are captured. - 1953: Crick and Watson reveal the structure of DNA. - 1956: Synthetic DNA is created. - 1966: DNA is discovered in both chromosomes and mitochondria. - 1969: The first individual gene is isolated. - 1970: The first artificial gene is synthesized.
