Which of the following is true about the inheritance of marker chromosomes?

Marker chromosomes are extra, small chromosomes that do not have an easily identifiable structure or function compared to standard chromosomes. Option B is accurate because studies have shown that about one-third of individuals with marker chromosomes can inherit them without exhibiting symptoms. This indicates that the presence of a marker chromosome does not always translate to a phenotypic impact, highlighting the variability in gene expression and the complexity of genetic inheritance.

In contrast, the other statements do not hold. The idea that marker chromosomes are always symptomatic when inherited is incorrect, as many individuals can carry them asymptomatically. The assertion that they cannot be passed to offspring overlooks the instances where inherited marker chromosomes do occur, which supports the validity of option B. Lastly, while some marker chromosomes may arise from de novo mutations, many others can be inherited from a parent, which means it’s not accurate to classify them all as always resulting from de novo changes. Understanding these aspects of marker chromosomes is critical for genetic counseling and risk assessment in families affected by these chromosomal anomalies.