Question

In a family, mother is affected by Down's syndrome and father is normal then what will be the percentage of affected offspring?

• A. 50%
• B. 100%
• C. 25%
• D. 75%

Answer 1

The correct option is A 50%

Down's syndrome is the result of trisomy in which chromosome number 21st contains an extra copy of chromosome (2A + 1). Affected mother will produce 50% normal egg cells and rest 50% eggs are of abnormal type.



In this case, percentage of affected offspring will be 50%.