Final answer:
Genes are characterized as a unit of heredity and a sequence of DNA that encodes a specific function, rather than a physical trait or a sequence of amino acids. Genes determine the traits of an organism by coding for proteins.
Step-by-step explanation:
The characteristics of genes include being a unit of heredity and a sequence of DNA that encodes a particular function. Hence, for the selection question regarding genes, the correct options would be a and b. Specifically, a gene is the physical and functional unit of heredity; it is a section of DNA that contains the information necessary to code for a specific protein or RNA molecule, which ultimately leads to the expression of a particular trait within an organism. Genes are linearly arranged on chromosomes and specify the sequences of amino acids, which are the building blocks of proteins. The observable traits expressed by an organism, known as the phenotype, result from the expression of these genes. Additionally, hereditary information is stored in DNA, and the basic unit of heredity is determined by the arrangement of nucleotides (cytosine, thymine, adenine, and guanine) in the genes. It is worth noting that a gene is not a sequence of amino acids or a physical trait; these are outcomes of gene expression.