The most common reason a physician might recommend that a woman have maternal serum screening and a karyotype analysis is concern that her fetus may have Down syndrome. Go to the OMIM website at www.ncbi.nlm.nih.gov/omim and look up Down syndrome (OMIM 190685).

Look at the 'Mapping' and 'Molecular Genetics' sections and describe what is meant by the Down syndrome critical region (DSCR).

Key Concepts

Down Syndrome

Down syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21. This condition leads to developmental delays, characteristic physical features, and an increased risk of certain health issues. Understanding the genetic basis of Down syndrome is crucial for recognizing its implications and the importance of prenatal screening.

Down Syndrome Critical Region (DSCR)

The Down syndrome critical region (DSCR) refers to a specific segment of chromosome 21 that is believed to contain genes that contribute to the phenotypic features of Down syndrome. Research indicates that the genes within this region may play roles in cognitive function, heart development, and other physiological processes. Identifying the DSCR helps in understanding the genetic mechanisms underlying the disorder.

Karyotype Analysis

Karyotype analysis is a laboratory technique used to visualize an individual's chromosomes to assess their number and structure. This analysis can identify chromosomal abnormalities, such as an extra chromosome 21 in Down syndrome. It is a critical tool in prenatal screening, allowing physicians to diagnose genetic conditions and inform expectant parents about potential health implications for their fetus.