Which genetic concept is characterized by the presence of different alleles for a given gene?

• A. Homozygosity
• B. Heterozygosity
• C. Diploidy
• D. Monogenic inheritance

Answer: (B)

The presence of different alleles for a given gene is known as heterozygosity. When an individual carries two different alleles for a particular gene, they are considered heterozygous for that gene. This genetic arrangement can occur in diploid organisms, which contain two sets of chromosomes—one from each parent—allowing for the possibility of having different alleles at the same locus.

In contrast, homozygosity refers to having two identical alleles for a gene, which would not apply here since the question specifically looks for differing alleles. Diploidy itself describes the condition of having two sets of chromosomes but does not inherently indicate whether the alleles are the same or different. Monogenic inheritance refers to traits determined by a single gene, without delving into the concept of alleles being distinct from one another.

In summary, heterozygosity is accurately defined as the presence of different alleles for a given gene, highlighting the genetic diversity within an individual's genotype.