Question

Total number of base pairs found in the human genome is?
A. 3.5 million
B. 35000
C. 35 billion
D. 3.1 billion

Answer 1

In double-stranded nucleic acids such as DNA, two nucleotide bases (on opposite strands) form a pair through hydrogen bonding. The chemical bases that make up the human genome are Adenine, Guanine, Cytosine, and Thymine. The term ‘base pair’ is used as a unit of quantification of the amount of DNA in a genome.

Complete answer:
The total number of base pairs found in the human genome is 3.1 billion.
There are 23 pairs of chromosomes in humans – 22 pairs are autosomes, while 1 pair constitute the sex chromosomes. The 3.1 billion base pairs are found in these chromosomes.
- A base pair is always formed between a purine and a pyrimidine.
- Purines – Adenine and Guanine
- Pyrimidines – Cytosine and Thymine
- Adenine (A) binds to Thymine (T) with 2 hydrogen bonds.
- Guanine (G) binds to Cytosine (C) with 3 hydrogen bonds.
- The number of base pairs in one DNA molecule is equal to the number of nucleotides in one strand.
- This base-pairing makes the double-stranded nature of DNA possible.
Basically, the base pairs help in establishing a relationship between the basic units of the strands of DNA.

Hence, the correct answer is option (D).

Note: The human genome consists of coding genes and non-coding genes. There are approximately 20,000 to 25,000 coding genes in the human genome. The genome is not uniform among all human beings. Except for monozygotic twins, no 2 humans have the same sequence in their DNA. Variations, defects, and diseases can arise as a result of changes in the genome due to mutations, deletions, and duplications.