Question

The approximate number of genes contained in the human genome is

• A. 40,000
• B. 30,000
• C. 80,000
• D. 1,00,000

Hint:

Post-Human Genome Project sequencing puts the count near 30,000, not the older 80,000-100,000 estimate.

Answer 1

The Correct Option is B

This question is really about how the estimated gene count of the human genome changed once scientists could actually read the full DNA sequence instead of guessing from its length.

1. 40,000: This number is higher than the confirmed count from genome sequencing and does not match the figure reported once the Human Genome Project finished its analysis.
2. 30,000: This is the figure that came directly out of the completed genome sequence in the early 2000s, later narrowed further to about 19,000 to 20,000 protein coding genes with better annotation. Of the four choices, it sits closest to the real, confirmed number.
3. 80,000: This was an older, pre-sequencing estimate used in some classic textbooks, based on rough calculations rather than actually reading the genome. It is now known to be far too high.
4. 1,00,000: This was the earliest and roughest guess, also from before the genome was sequenced, and is even further from the true figure.

Once the human genome was fully sequenced, the gene count dropped to roughly 30,000 and was later refined closer to 20,000. So the best answer among the given options is 30,000, not the older textbook figure of 80,000 or 100,000.

Let's summarize:

• Pre-sequencing textbooks guessed 80,000 to 100,000 genes based on DNA length alone.
• Direct sequencing in the Human Genome Project brought the real count down to about 30,000, later refined to about 20,000.

So the approximate number of genes in the human genome, based on actual sequencing data, is 30,000.