Total number of genes in a human being is
**Core Concept**
The human genome is the complete set of genetic instructions encoded in DNA, which determines the characteristics and traits of an individual. The total number of genes in the human genome is a critical aspect of understanding the complexity of human biology and disease.
**Why the Correct Answer is Right**
The human genome is estimated to contain approximately 20,000 to 25,000 protein-coding genes, according to the National Human Genome Research Institute. This number has been refined over time as genomic sequencing technologies have improved. The non-coding regions of the genome, which make up a significant portion of the total DNA, do not code for proteins but instead regulate gene expression and perform other essential functions.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it underestimates the number of genes in the human genome. While some sources may have initially suggested a lower number, subsequent studies have consistently shown that there are more genes than previously thought.
**Option B:** This option is incorrect because it overestimates the number of genes in the human genome. While some genes may have multiple isoforms or variants, the overall number of genes is still in the range of 20,000 to 25,000.
**Option C:** This option is incorrect because it is too vague and does not provide a specific number. While the human genome is complex and contains many genes, a specific number is needed to accurately answer the question.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the number of genes in the human genome is still a subject of ongoing research and refinement. However, the current estimate of 20,000 to 25,000 protein-coding genes provides a useful benchmark for understanding the complexity of human biology and disease.
**Correct Answer:** C. 20,000 to 25,000