Question

The shorter and longer arms of a submetacentric chromosome are referred to as:

• A. s-arm and l-arm respectively
• B. p-arm and q-arm respectively.
• C. q-arm and p-arm respectively
• D. m-arm and n-arm respectively

Answer 1

The Correct Option is B

In chromosomes, the different segments have specific names based on the location of the centromere. In a submetacentric chromosome, the centromere is slightly off-center, resulting in one arm being longer than the other. Therefore, the arms are distinguished as follows:

1. The shorter arm of the chromosome is termed the "p-arm."
   • The letter "p" stands for "petite," which means small in French. Thus, the shorter segment is referred to as the p-arm.
2. The longer arm of the chromosome is known as the "q-arm."
   • There is no specific association of "q" with a word meaning longer; it follows alphabetically after "p."

The conventions for these names ensure consistency when discussing chromosomes in genetics and cytogenetics. This method of denoting arms also allows easy identification and communication concerning cytogenetic activities.

Thus, the correct answer is: p-arm and q-arm respectively.

The other options can be ruled out as follows:

• s-arm and l-arm respectively: These terms are not conventionally used to describe the arms of chromosomes.
• q-arm and p-arm respectively: This ordering is incorrect as the p-arm is always the shorter arm.
• m-arm and n-arm respectively: These are also not standard terms used to describe the chromosome arms.