Which statement regarding partial chromosomal deletions or duplications reflects the cause of manifestations?
A)They result in either a triple dose of some gene alleles or a single dose of some alleles.
B)They usually result in fewer or milder manifestations than do trisomies or monosomies.
C)The manifestations are unpredictable because they commonly vary depending on parental origin.
D)General prenatal chromosomal analysis has resulted in fewer children being born with these problems.

Question

Quizplus · Accepted Answer

Chromosome duplications in coding regions result in having a triple dose of some gene alleles. Deletions in coding regions result in a single dose of some alleles. When the duplicated or deleted chromosome material of a gene-coding region is present in most or all of an affected person's tissues, it is usually accompanied by many anatomic and functional problems. These problems may be as severe or more severe than those seen in common trisomies or monosomies.
Chromosomal analysis of duplications and deletions is not sufficient to determine how many copies of gene alleles are affected because a duplication or deletion large enough to be visualized on chromosomal analysis must contain at least a minimum of 200,000 bases. Duplications and deletions do not have to be this large to cause anatomic and functional problems. Partial duplications and deletions are random events resulting from chromosomal breakage and structural rearrangement, usually during gametogenesis.

Which Statement Regarding Partial Chromosomal Deletions or Duplications Reflects the Cause