Final answer:
A gene is a DNA segment with instructions for making a specific polypeptide chain, which forms part of a protein. Genes are found on chromosomes within the cell nucleus, and they play a crucial role in heredity and the cell's functioning. Transcription is how genes code for proteins, with constitutive genes maintaining basic cell functions.
Step-by-step explanation:
A gene is a segment of deoxyribonucleic acid (DNA) that contains the instructions for making a specific polypeptide chain, which when combined with other polypeptide chains, forms a protein. Proteins are essential for carrying out various functions within the cell. Genes are linearly arranged on chromosomes, which are larger structures located in the nucleus of every cell that controls hereditary traits passed from parents to offspring.
Transcription is the process through which a segment of DNA is copied into messenger RNA (mRNA), which then leaves the cell nucleus and is used in the synthesis of polypeptide chains. These chains are the building blocks of proteins, and each chain is coded for by a different gene. The genetic code within a gene is organized in a series of three-letter codes, called codons, which correspond to specific amino acids or signals that initiate or terminate protein synthesis.
There are also constitutive genes, sometimes known as housekeeping genes, which are constantly active within the cell to maintain basic functions. Given the integral role of genes in the biology of organisms, genetic research involves not only understanding how traits are inherited and expressed but also addressing ethical and legal issues, such as genetic discrimination, which is now legally protected against in the United States by the Genetic Information Nondiscrimination Act of 2008.