General Characteristics
How many chromosomes does a person with Down syndrome usually have?
47
What is the name of the error in cell division that usually causes Down syndrome?
Nondisjunction
What condition involving muscle tone is particularly common in infants with Down syndrome?
Hypotonia
What is the percentage (%) of Down Syndrome cases with Trisomy 21?
The extra chromosome affects both physical and cognitive development. What molecule found in chromosomes contains the instructions for how the body develops and functions?
DNA.
What happens to chromosome 21 during nondisjunction?
It fails to separate properly, causing a reproductive cell to receive two copies instead of one.
A child with Down syndrome may sit, crawl, and walk later than other children. What type of symptoms do these represent?
Developmental symptoms
Mention the two other types of Down Syndrome aside from Tisomy 21.
Translocation Down Syndrome, Mosaic Down Syndrome
Why is Down syndrome classified as a chromosomal genetic disorder rather than a disease?
Because it results from an extra chromosome rather than something that can be caught or spread.
What is the most common type of Down syndrome?
Trisomy 21
A baby with Down syndrome has a significantly increased risk of a condition affecting the structure of the heart from birth. What condition is this?
Congenital heart defect
What type of test can confirm Down syndrome after birth by examining the baby's chromosomes?
Karyotype test
Name two general characteristics associated with Down syndrome.
Mild to moderate intellectual disability.
Slower physical growth and development.
Delayed speech and language skills.
Characteristic facial features. (Shown in image)
Low muscle tone (hypotonia).
Increased risk of certain health conditions.
What percentage of Down syndrome cases are approximately Trisomy 21?
About 95%
Name two different body systems or functions that can be affected by health conditions associated with Down syndrome
Possible answers: hearing, vision, thyroid function, digestion, sleep, and the immune system.
What is the key difference between prenatal screening and prenatal diagnostic testing?
Screening estimates the chance of Down syndrome, while diagnostic testing can confirm whether the baby has it.
Explain why having an extra chromosome can affect many different parts of the body rather than producing only one symptom.
The chromosome contains DNA and genes that influence how the body and brain develop, so an extra copy can affect multiple aspects of development and health.
What is the difference between mosaic Down syndrome and translocation Down syndrome?
In mosaic Down syndrome, only some cells have an extra chromosome 21. In translocation Down syndrome, the extra chromosome 21 is attached to another chromosome.
Which condition can occur later in adulthood at a younger age in people with Down syndrome, and why is it an important area of current research?
Alzheimer's disease
A prenatal screening test indicates a high risk of Down syndrome. Name one of the two diagnostic tests could doctors use to confirm the diagnosis?
Chorionic Villus Sampling (CVS) or amniocentesis.