12 Questions
What physical features are commonly seen in patients with Down syndrome?
A flat bridge of nose, slanted eyes, and prominent palpebral fissures
What percentage of spontaneous abortions have a demonstrable chromosomal abnormality?
50%-60%
What is the term for the phenomenon where chromosomally abnormal conceptuses are eliminated through abortion during pregnancy?
Biological elimination
Which of the following syndromes has the highest rate of biological elimination?
Turner's syndrome
What is the relationship between chromosome number and degree of biological elimination?
Inversely proportional
What is the approximate percentage of conceptuses with chromosomal abnormalities that are born alive?
6%-7%
What is the primary application of clinical cytogenetics?
Diagnosis and management of genetic disorders
In which of the following individuals can cytogenetic abnormalities be found?
In all individuals, including those with normal phenotypes
What is the primary goal of prenatal cytogenetics?
To detect genetic abnormalities in embryos before birth
What is the characteristic of a syndrome in clinical cytogenetics?
A group of clinical features seen in several unrelated individuals with a common chromosomal basis
What is the significance of childhood and adult cytogenetics?
It is used to detect genetic abnormalities that may manifest later in life
What is the primary advantage of clinical cytogenetics?
It can be used to diagnose genetic disorders at any stage of life
Study Notes
Clinical Cytogenetics
- Cytogenetic abnormalities can be found in: • Apparently normal individuals • Patients with phenotypic anomalies (e.g. cleft lip/palate) • Patients with diagnosed genetic disorders
- Diagnosis of cytogenetic disorders can be made at any stage of life: • Prenatal cytogenetics: genetic abnormalities diagnosed before birth • Postnatal cytogenetics: evidence of cytogenetic abnormalities sought after birth • Childhood and adult cytogenetics: genetic abnormalities manifest later in life
Syndromes
- A syndrome is established when the same set of features are seen in several unrelated individuals, assumed to have a common basis of specific chromosomal abnormalities
- These syndromes may occur in different degrees (mild, moderate, or severe manifestations)
- Example: Down syndrome • Characterized by flat bridge of nose, slanted eyes, prominent palpebral fissures • Patients have intellectual disabilities and cardiovascular defects
Prenatal Cytogenetics
- 50%-60% of spontaneous abortions (miscarriages) during early pregnancy have a demonstrable chromosomal abnormality
- 52% of these are autosomal trisomies
- 1 in 3 conceptuses have chromosomal abnormality, but only 6:1000 live births due to biological elimination of recognized errors
- Rate of biological elimination: • 95% of 45, X (Turner's Syndrome) • 90% of Trisomy 13 (Patau Syndrome) • 80% of Trisomy 18 (Edwards Syndrome) • 65% of Trisomy 21 (Down syndrome)
- Biological elimination is inversely proportional to chromosome number, while survival is directly proportional
This quiz covers the basics of clinical cytogenetics, including cytogenetic abnormalities, diagnosis, and syndromes. Learn about prenatal cytogenetics, chromosomal abnormalities, and specific syndromes like Down syndrome.
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