The DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones
Genes can be described as segment of DNA (deoxyribonucleic acid) that code for specific protein, which ultimately determines the trait or characteristic of an organism (such as eye color, hair color).
They are considered as the unit of heredity as they are passed from one generation to the next generation through chromosomes.
Thus, genes is the right answer for the given blank.
