Humber Admissions Practice Test

How many forms of alleles does a heterozygous organism possess?

1. Zero

2. One

3. Two

4. Three

The correct answer is: Two

A heterozygous organism possesses two different forms of alleles for a particular gene. In genetics, alleles are variations of a gene that can produce different traits. When an organism is described as heterozygous, it means it has inherited two different versions of a gene—one from each parent. For instance, if we consider a gene that determines flower color, one allele might code for red flowers while another codes for white flowers. In the case of a heterozygous plant, it carries both the red and white alleles, resulting in a mix of traits that may produce a phenotype that is distinct from both homozygous conditions (where both alleles are the same). Therefore, the presence of two distinct alleles is what defines a heterozygous state, making it possible for the organism to express a dominant trait or, in some cases, a combination of traits. Other answer choices do not align with the definition of heterozygous. Zero, one, and three do not reflect the key concept that a heterozygous individual specifically possesses two different alleles for the same gene.