Question

which of the following statements correctly describes aneuploid conditions?
an aneuploidy resulting in the deletion of a chromosome segment is less serious than a duplication.
of all human aneuploidies, only down syndrome is associated with developmental delays or subnormal intelligence.
monosomy x is the only known viable human monosomy.
a monosomy is more frequent than a trisomy.

Explanation:

• Monosomy X (Turner syndrome) is the only viable monosomy in humans. Most other monosomies are lethal during embryonic development.
• Trisomies are more common than monosomies. For example, trisomy 21 (Down syndrome), trisomy 18, and trisomy 13 are relatively more frequently observed compared to monosomies (except Monosomy X).
• Deletion of a chromosome segment is generally more serious than duplication. Deletion often leads to loss of gene function, and since genes are essential for normal biological processes, the effects can be severe. In contrast, duplication may lead to over - expression of genes, but cells may have some tolerance mechanisms.
• Not only Down syndrome (trisomy 21) is associated with developmental delays or subnormal intelligence. Other aneuploidies like trisomy 18 (Edwards syndrome) also have significant developmental problems.

Answer:

Monosomy X is the only known viable human monosomy.