Explain why diploid organisms will have a genotype that is composed of two alleles for a particular gene

Diploid organisms have two sets of chromosomes, one from each parent. This means that for each gene, a diploid organism has two versions, or alleles. These alleles may be the same (homozygous) or different (heterozygous).

Here are the steps explaining why:

1. Sexual reproduction involves the fusion of two gametes (sperm and egg cells), each of which is haploid, meaning it contains one set of chromosomes.

2. Each of these gametes carries one allele for each gene. The specific allele that a gamete carries for each gene is determined randomly during meiosis, the process that produces the gametes.

3. When the sperm and egg fuse during fertilization, the resulting offspring is a diploid organism, meaning it has two sets of chromosomes.

4. Therefore, for each gene, the offspring has two alleles: one from the mother (via the egg) and one from the father (via the sperm).

5. These two alleles together make up the genotype of the organism for that particular gene.

So, the diploid nature of these organisms is what leads to them having a genotype composed of two alleles for each gene.