A is a series of nucleotides that encodes a protein product. This coding DNA may have different forms, or varieties, called . An individual with two different versions of a gene is genetically . In traits with a simple pattern of inheritance, only the trait conferred by the form of the gene will be visible. The other form of the gene is : it confers a trait that is only visible when the individual is genetically , or has two identical copies of the gene.

A nucleotide can be defined as an organic molecule which forms the building block of nucleic acid such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

Basically, nucleotide comprises of the following parts;

1. Nitrogenous base: this includes adenine (A), thymine (T), guanine (G), and cytosine (C) which are mainly found in the DNA while adenine (A), guanine (G), uracil (U) and cytosine (C) are found in the RNA.

2. A phosphate group.

3. A penrose sugar: it is either deoxyribose in DNA or ribose in RNA.

The two parts or chemical components of a nucleotide which do not change throughout the structure of DNA are;

I. Five-Carbon Sugar also known as deoxyribose and it has hydrogen on its second carbon.

II. Phosphate: this is the structural backbone that provides support to DNA.

Filling up the blanks in the question, we have;

A gene is a series of nucleotides that encodes a protein product. This coding DNA may have different forms, or varieties, called alleles. An individual with two different versions of a gene is genetically heterozygous. In traits with a simple pattern of inheritance, only the trait conferred by the dominant form of the gene will be visible. The other form of the gene is recessive: it confers a trait that is only visible when the individual is genetically homo-zygous, or has two identical copies of the gene.