Question

Write the number of chromosomes in trisomic and monosomic conditions in humans.

Hint:

Remember: Normal = 46, Trisomy = 47 (extra), Monosomy = 45 (missing).

Answer 1

Step 1: Normal chromosome number in humans.
Humans normally have 46 chromosomes (23 pairs). This is the diploid number (2n = 46).

Step 2: Trisomic condition.
\[\begin{array}{rl} \bullet & \text{Trisomy occurs when one extra chromosome is present (2n + 1).} \\ \bullet & \text{In humans: $46 + 1 = 47$ chromosomes.} \\ \bullet & \text{Example: Down's Syndrome (Trisomy 21).} \\ \end{array}\]

Step 3: Monosomic condition.
\[\begin{array}{rl} \bullet & \text{Monosomy occurs when one chromosome is missing (2n – 1).} \\ \bullet & \text{In humans: $46 - 1 = 45$ chromosomes.} \\ \bullet & \text{Example: Turner's Syndrome (45, XO).} \\ \end{array}\]

Step 4: Conclusion.
\[ \text{Trisomy = 47 chromosomes, Monosomy = 45 chromosomes in humans.} \]