What is a gene?
A. a section of DNA that encodes a specific protein
B. a structure that contains many chromosomes
C. a large molecule that performs a specific function
D. a point that joins two halves of a chromosome
A. a section of DNA that encodes a specific protein
A. a section of DNA that encodes a specific protein
The correct answer is A. A gene is a section of DNA that encodes a specific protein. To understand this, we need to break down the options and explain how to arrive at the answer.
Option A: A gene is a section of DNA that encodes a specific protein. This is the correct answer. Genes are units of heredity that contain instructions for building and maintaining living organisms. They specify the sequence of amino acids in a protein, which determines its structure and function. Genes are made up of DNA, and different genes control various traits and characteristics.
Option B: A structure that contains many chromosomes. This is not the definition of a gene. Chromosomes are structures within the nucleus of cells that carry genes. Each chromosome contains many genes, but a gene itself is not a structure that contains chromosomes.
Option C: A large molecule that performs a specific function. While genes are made up of molecules (DNA), they are not molecules themselves. Genes are sections of DNA that provide instructions for the synthesis of proteins, which then perform specific functions in cells.
Option D: A point that joins two halves of a chromosome. This is not the definition of a gene. Chromosomes consist of two identical halves (chromatids) that are joined at a point called the centromere. A gene, however, is a specific section of DNA within a chromosome, not the point of joining.
In summary, a gene is a section of DNA that encodes a specific protein, making option A the correct answer.