Concept:A gene is the basic physical and functional unit of heredity, made of a segment of DNA.
Explanation:Heredity is the passing of traits from parents to offspring.
A gene is a specific segment of DNA present on chromosomes.
Each gene carries a code that determines the inherited characteristics of an individual.
Genes code for functional proteins in the body.
Genes are passed from one generation to the next.
The human genome contains about 30,000 genes.
Dystrophin is the largest known human gene, consisting of around 2.4 million bases.
Chromosomes carry genes, but they are not the basic unit of heredity.
A zygote is a single cell formed after fertilization, not a unit of heredity.
Thus, the basic unit of heredity is the gene.
Answer:A. gene