Which statement best defines haploid in terms of chromosome sets?

Which statement best defines haploid in terms of chromosome sets?

• A. A single set of chromosomes and genes
• B. Two complete sets
• C. Three copies of chromosomes
• D. Four copies of genes

Answer: (A)

Haploid describes a cell with a single complete set of chromosomes, meaning one copy of each chromosome and, for most genes, one allele per gene present in that genome. This is the form gametes carry in sexually reproducing organisms, since the haploid set combines with another haploid set during fertilization to restore the diploid number. In humans, that haploid set consists of 23 chromosomes. The alternative ideas describe having two, three, or four complete sets of chromosomes, which would be diploid, triploid, or tetraploid, respectively, and do not define haploid.

Haploid describes a cell with a single complete set of chromosomes, meaning one copy of each chromosome and, for most genes, one allele per gene present in that genome. This is the form gametes carry in sexually reproducing organisms, since the haploid set combines with another haploid set during fertilization to restore the diploid number. In humans, that haploid set consists of 23 chromosomes. The alternative ideas describe having two, three, or four complete sets of chromosomes, which would be diploid, triploid, or tetraploid, respectively, and do not define haploid.