Final answer:
Gregor Mendel discovered that genes are the fundamental unit of heredity. They are located on chromosomes and are responsible for the traits that an organism exhibits. The expression of genes produces the observable traits, or phenotype, of an organism.
Step-by-step explanation:
Gregor Mendel discovered that genes are the fundamental unit of heredity.
Genes are best understood as the sequence or ordering of the DNA material that is housed in the nucleus.
They are located on chromosomes and are responsible for the traits that an organism exhibits.
The expression of genes produces the observable traits, or phenotype, of an organism.
Sometimes, genes can have variations called alleles, which are similar but slightly different forms of the same gene.