Question

question 50
1 pts
an individual with down syndrome has three copies of chromosome 21. would all children of an individual with down syndrome also have down syndrome?
no, only 25 percent of the eggs or sperm formed would have an extra copy of the chromosome.
yes, all children would also have three copies of chromosome 21.
no, only 75 percent of the eggs or sperm formed would have an extra copy of the chromosome.
no, only 50 percent of the eggs or sperm formed would have an extra copy of the chromosome.

Explanation:

Down syndrome is typically caused by an error in cell division (nondisjunction) during gamete formation. An individual with Down syndrome (trisomy 21) has 47 chromosomes (45 autosomes + XX or XY). During meiosis, when gametes (eggs or sperm) are formed, the extra chromosome 21 can segregate in different ways. Half of the gametes will receive the extra chromosome 21 (n + 1) and half will receive the normal number (n). So, only 50% of the eggs or sperm formed would have an extra copy of chromosome 21.

Answer:

No, only 50 percent of the eggs or sperm formed would have an extra copy of the chromosome.