In humans, how are chromosome numbers assigned according to the size ordering system?

• A. Chromosome 1 is the largest and numbers decrease with decreasing size.
• B. Chromosome numbers are assigned randomly without regard to size.
• C. Sex chromosomes are always numbered first because they are the largest.
• D. Chromosome 22 is the largest and numbers increase with increasing size.

Answer: (A)

Verified step by step guidance

1. Understand that human chromosomes are numbered based on their size, with the largest chromosome assigned the smallest number.
2. Recognize that chromosome 1 is the largest human chromosome, so it is assigned the number 1.
3. Know that the numbering continues in decreasing order of size, so chromosome 2 is the second largest, chromosome 3 the third largest, and so on.
4. Note that sex chromosomes (X and Y) are not included in this size-based numbering system; they are labeled separately.
5. Conclude that the correct system assigns chromosome numbers starting from the largest (chromosome 1) to the smallest (chromosome 22) based on size.