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).
List the main symptoms of Down syndrome.

Verified step by step guidance

1. Understand that Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21, also known as trisomy 21.
2. Go to the OMIM website at www.ncbi.nlm.nih.gov/omim and enter the OMIM number 190685 or search for 'Down syndrome' to access detailed genetic and clinical information.
3. Locate the section on the OMIM page that describes the clinical features or main symptoms associated with Down syndrome.
4. Identify and list the common symptoms, which typically include intellectual disability, characteristic facial features, hypotonia (low muscle tone), and congenital heart defects, among others.
5. Summarize the main symptoms clearly, ensuring you capture both physical and developmental characteristics as described in the OMIM entry.

Key Concepts

Down Syndrome and Its Genetic Basis

Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21 (trisomy 21). This chromosomal abnormality leads to developmental and physical changes, including intellectual disability and characteristic facial features. Understanding its genetic cause is essential for interpreting karyotype results.

Maternal Serum Screening

Maternal serum screening is a prenatal test that measures specific proteins and hormones in a pregnant woman's blood to assess the risk of chromosomal abnormalities like Down syndrome. It is a non-invasive method used to identify pregnancies that may require further diagnostic testing.

Karyotype Analysis

Karyotype analysis is a laboratory technique that visualizes an individual's chromosomes under a microscope to detect numerical or structural abnormalities. In prenatal diagnosis, it confirms the presence of trisomy 21 by identifying the extra chromosome responsible for Down syndrome.