PATHOLOGY

Detailed explanation-1: -A gene is a short section of DNA. DNA is made up of millions of small chemicals called bases. The chemicals come in four types A, C, T and G. A gene is a section of DNA made up of a sequence of As, Cs, Ts and Gs.

Detailed explanation-2: -Genes are made up of DNA. Some genes act as instructions to make molecules called proteins. However, many genes do not code for proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases.

Detailed explanation-3: -DNA has a double-helical structure with two nucleotide chains that run anti-parallel, the outer edges are formed by alternating deoxyribose sugar molecules and phosphate groups, which make up the sugar-phosphate backbone. Hence statement 3 is correct.

Detailed explanation-4: -Genes are made from DNA and serve as a functional units of heredity. Thus, one gene can code for your eye color, while another codes for your hair texture etc. Therefore, choice 4 is the correct choice: genes are made of DNA and code for proteins.