The condition in which the individual possessing chromosome constitution of 2n − 1 is referred to as

Correct option is A

• Explanation:
• Monosomy refers to the loss of one chromosome from the normal diploid set.
• In monosomic condition, the chromosome number is 2n − 1.
• The individual lacks one member of a homologous chromosome pair.
• This condition commonly arises due to nondisjunction during meiosis.
• Information booster (related facts):
• Normal diploid chromosome number is denoted by 2n.
• Aneuploidy is a condition involving gain or loss of one or more chromosomes.
• Monosomics are important tools in cytogenetic and genetic studies, especially in crop improvement.
• Aneuploid conditions generally reduce fertility and vigor.
• Why other options are incorrect:
• (b) Double monosomic
• Chromosome constitution is 2n – 1– 1.
• Two different chromosomes are missing, not one.
• (c) Trisomic
• Chromosome constitution is 2n + 1.
• One extra chromosome is present instead of one missing.
• (d) Double trisomic
• Chromosome constitution is 2n + 2.
• Two extra chromosomes are present, not a deficiency.