Question:
The approximate number of genes contained in the human genome is
The approximate number of genes contained in the human genome is
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Post-Human Genome Project sequencing puts the count near 30,000, not the older 80,000-100,000 estimate.
Updated On: Jul 8, 2026
- 40,000
- 30,000
- 80,000
- 1,00,000
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Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Step 1: Understanding the Question:
The question asks for the approximate total number of genes in the human genome, a number that has changed over the years as sequencing technology improved.
Step 2: Historical background.
Before the Human Genome Project, older textbooks like Harrison's and Harper's estimated the human genome to hold about 100,000 genes. This figure was a rough guess based on the total DNA length and did not come from actually reading the sequence.
Step 3: What the completed genome sequence showed.
When the draft human genome sequence was published in the early 2000s, direct counting brought the estimate down sharply, first to about 30,000 to 35,000 genes, later refined further with modern annotation to about 19,000 to 20,000 protein coding genes. This was a surprise at the time, since it is not very different from the gene count of much simpler organisms.
Step 4: Why the older answer of 80,000 or 100,000 no longer holds.
Options like 80,000 and 100,000 reflect the pre-genome-project era guesses and are now known to be well above the real count. Even 40,000 overshoots the confirmed number. Among the choices given, 30,000 is the closest to the actual, sequence-based figure and matches what the Human Genome Project itself reported once the genome was fully read.
Note on the answer key: The original paper's key marked 80,000 as correct, following older references such as Harrison and Harper, but its own cited note (CMDT 2002 and the Human Genome Project data) already flags 30,000 as the updated, more accurate figure. Since current genomic annotation firmly supports a count far closer to 30,000 (in fact closer to 20,000) than to 80,000 or 100,000, this solution takes 30,000 as the best answer among the options offered.
Step 5: Final Answer:
The approximate number of genes in the human genome is about 30,000, option (2).
The question asks for the approximate total number of genes in the human genome, a number that has changed over the years as sequencing technology improved.
Step 2: Historical background.
Before the Human Genome Project, older textbooks like Harrison's and Harper's estimated the human genome to hold about 100,000 genes. This figure was a rough guess based on the total DNA length and did not come from actually reading the sequence.
Step 3: What the completed genome sequence showed.
When the draft human genome sequence was published in the early 2000s, direct counting brought the estimate down sharply, first to about 30,000 to 35,000 genes, later refined further with modern annotation to about 19,000 to 20,000 protein coding genes. This was a surprise at the time, since it is not very different from the gene count of much simpler organisms.
Step 4: Why the older answer of 80,000 or 100,000 no longer holds.
Options like 80,000 and 100,000 reflect the pre-genome-project era guesses and are now known to be well above the real count. Even 40,000 overshoots the confirmed number. Among the choices given, 30,000 is the closest to the actual, sequence-based figure and matches what the Human Genome Project itself reported once the genome was fully read.
Note on the answer key: The original paper's key marked 80,000 as correct, following older references such as Harrison and Harper, but its own cited note (CMDT 2002 and the Human Genome Project data) already flags 30,000 as the updated, more accurate figure. Since current genomic annotation firmly supports a count far closer to 30,000 (in fact closer to 20,000) than to 80,000 or 100,000, this solution takes 30,000 as the best answer among the options offered.
Step 5: Final Answer:
The approximate number of genes in the human genome is about 30,000, option (2).
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