What is a gene?

a. the different forms of a trait

b. a segment of dna that is the basic unit of heredity

c. the appearance or characteristics that are seen in an organism

d. an organism's allele combination

Gene is the appearance or characteristics that are seen in an organism, It is also an organism's allele combination and a segment of DNA that is the basic unit of heredity

Explanation:

Gene is defined as a unit of heredity by which genetic information is transferred from parents to its offspring. The genes are present on the chromosomes as bead-like structures. Genes are made up of  DNA sequence which dictates specific protein to be made in organisms. Genes are responsible for all the inherited characters in an organism.

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.

the answer is c.mitochondria. glad to .