Question

The modern concept of a gene is
A. A segment of DNA capable of crossing over
B. A functional unit of DNA
C. A segment of DNA
D. A segment of chromosome

Answer 1

Hint: In biology, a gene is a sequence of nucleotides in DNA or RNA. It encodes the synthesis of a gene product either RNA or protein. During a gene expression, the DNA is first copied into RNA and then RNA can be directly functional or be the intermediate template for a protein that performs a function.

Complete answer: A gene is a segment of DNA. It contains the information for one enzyme or one polypeptide chain which is coded in the language of nitrogenous bases or the nucleotides. A gene is the molecular unit of heredity of any living organism. Genes are made of DNA. It is the genome itself. A gene consists of enough DNA which codes for one protein. A genome is simply the sum total of DNA of an organism. The genes differ in three categories:
a) Regulation
b) Mutation rates
c) The types of a gene involved
Type I genes i.e. differed by regulation. They are involved in immune response or sensory receptors, while type III genes are differed by their gene type and are involved in cell to cell signalling and type II genes, differed on the basis of their mutation rates. They are a complex mix of all three types.
Thus, the correct answer is option B.

Note: Some genes act as instructions to make protein molecules but many genes do not code for proteins. In humans, genes vary in size ranging from a few hundred DNA bases up to more than 2 million bases. The translation is the process that leads to the formation of a protein.