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Questions and Answers
What percentage of Down syndrome cases are attributed to mosaicism?
What percentage of Down syndrome cases are attributed to mosaicism?
Translocation Down syndrome accounts for about 5% of all cases.
Translocation Down syndrome accounts for about 5% of all cases.
False
What is the primary genetic cause of Down syndrome?
What is the primary genetic cause of Down syndrome?
an extra copy of chromosome 21
The chance of a 40-year-old woman having a child with Down syndrome is approximately 1 in _____.
The chance of a 40-year-old woman having a child with Down syndrome is approximately 1 in _____.
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Match the following types of Down syndrome with their characteristics:
Match the following types of Down syndrome with their characteristics:
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Which of the following is NOT a physical sign of Down syndrome?
Which of the following is NOT a physical sign of Down syndrome?
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Children with Down syndrome typically reach developmental milestones at the same pace as their peers.
Children with Down syndrome typically reach developmental milestones at the same pace as their peers.
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Name one cognitive symptom commonly associated with Down syndrome.
Name one cognitive symptom commonly associated with Down syndrome.
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One common behavioral symptom in children with Down syndrome is difficulty in communicating their ______.
One common behavioral symptom in children with Down syndrome is difficulty in communicating their ______.
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Match the developmental aspects to their corresponding descriptions for children with Down syndrome:
Match the developmental aspects to their corresponding descriptions for children with Down syndrome:
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Study Notes
Introduction
- Genes carry codes for inherited traits
- Genetic material stored in the nucleus of each cell
- Chromosomes are rod-like structures in the nucleus, each cell typically contains 23 pairs
- Half of the chromosomes are inherited from each parent
- Down syndrome occurs when an individual has a full or partial extra copy of chromosome 21
Types of Down Syndrome
- Trisomy 21 (Nondisjunction): An extra chromosome 21
- Mosaicism: A mixture of cells, some with the usual 46 chromosomes and some with 47
- The least common type (around 2% of cases)
- Translocation: The total number of chromosomes remains 46, but an extra full or partial copy of chromosome 21 attaches to another chromosome (often chromosome 14)
Causes
- Unknown cause for the extra full or partial chromosome 21
- Age of the mother is a contributing factor, higher chance in older women
- Approximately 5% of cases traced to the father
- Environment and parents' activities before or during pregnancy not a determining factor
Symptoms
- Physical:
- Flat nose bridge
- Slanted upward-pointing eyes
- Short neck
- Small ears, hands, and feet
- Weak muscle tone at birth
- Small pinky finger pointing inward
- One crease in palm
- Shorter than average height
- Behavioral:
- Stubbornness
- Tantrums
- Difficulty paying attention
- Obsessive or compulsive behaviours
- Cognitive:
- Developmental challenges
- Intellectual or developmental disabilities
- Difficulties with walking, speaking, learning and play
Commonness
- Approximately 1 in every 772 babies born in the United States have Down syndrome
- About 5,100 babies with Down syndrome are born in the United States each year.
Down Syndrome Discovery
- John Langdon Down, an English physician, described Down syndrome in 1866.
Diagnosis
- Physical appearance
- Karyotype: Blood test to determine chromosome structure
- Screening tests
- First trimester combined test: Blood test to measure pregnancy-related hormones and ultrasound to measure nuchal translucency
- Second trimester quad screen: Blood test to measure several pregnancy-related hormones
- Diagnostic tests
- Chorionic villus sampling (CVS): Performed early in pregnancy to analyze fetal chromosomes
- Amniocentesis: Performed later in pregnancy to analyze fetal chromosomes
Treatment
- Early intervention important
- Team approach involving:
- Primary care pediatrician
- Pediatric cardiologist
- Pediatric gastroenterologist
- Pediatric endocrinologist
- Developmental pediatrician
- Pediatric neurologist
- Pediatric eye specialist (ophthalmologist)
- Audiologist
- Speech pathologist
- Physical therapist
- Occupational therapist
- Organizations for support:
- Global Down Syndrome Foundation
- International Down Syndrome Coalition (IDSC)
- International Mosaic Down Syndrome Association (IMDSA)
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