A gene may have many alleles, but each individual has only two alleles because

Options

A. having more than two alleles is lethal
B. having more than two alleles unbalances the chromosomes.
C. a person has two parents who each contribute one allele.
D. a backup set of alleles is necessary in case something goes wrong.

Answer

**Step-by-Step Solution:**

1. **Understanding Alleles**: A gene is a segment of DNA that codes for a specific trait. Alleles are different versions of a gene that can exist at a specific locus on a chromosome. For example, a gene for flower color might have alleles for red, white, and yellow.

2. **Diploid Organisms**: Most organisms, including humans, are diploid, meaning they have two sets of chromosomes—one set inherited from each parent. Therefore, for any given gene, an individual can have two alleles (one from each parent).

3. **Multiple Alleles**: While a gene can have multiple alleles in a population (like the ABO blood group system), any individual can only possess two of these alleles. This is because they inherit one allele from each parent.

4. **Genetic Balance**: Having more than two alleles in an individual could lead to genetic imbalances and complications in gene expression. This is why individuals typically only have two alleles for each gene.

5. **Conclusion**: The presence of only two alleles in an individual is a consequence of being diploid. While multiple alleles can exist in a population, each individual can only express two alleles for a given gene.

**Final Answer**: A gene may have many alleles, but each individual has only two alleles because they are diploid organisms, inheriting one allele from each parent, and having more than two alleles could lead to genetic imbalances.

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