Questions and Answers
What is the primary genetic cause of cystic fibrosis?
Which of the following is NOT a clinical presentation of cystic fibrosis?
How does cystic fibrosis affect the pancreas?
Which of the following populations has the highest incidence of cystic fibrosis?
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What condition is commonly associated with male patients suffering from cystic fibrosis?
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What is the primary cause of phenylketonuria (PKU)?
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Which of the following is NOT a symptom associated with Tay-Sachs disease?
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Which genetic disorder is characterized by an atypical hemoglobin molecule called hemoglobin S?
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Children with untreated PKU are at risk of developing which condition?
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What condition is associated with the accumulation of GM2 ganglioside in neurons?
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Which disorder typically leads to the addition of a musty or mouse-like odor in infants?
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Xeroderma pigmentosum is primarily caused by mutations involved in which biological repair process?
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Which population is more commonly affected by Tay-Sachs disease?
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What is a common clinical presentation in individuals with sickle cell disease?
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What condition is characterized by infants appearing normal until 3-6 months of age?
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Study Notes
Autosomal Recessive Disorders
Cystic Fibrosis
- Caused by mutations in the CFTR gene, which encodes a chloride channel.
- Disruption of chloride and water flow affects mucus layer in airways, digestive, and reproductive systems.
- Severity influenced by genetic and environmental factors.
- Clinical symptoms include:
- Breathing difficulties and recurrent lung infections.
- Permanent lung damage with scar tissue and cyst formation.
- Gastrointestinal issues: meconium ileus in newborns and oily stools.
- Pancreatic damage leads to cystic fibrosis-related diabetes mellitus (CFRDM).
- Congenital bilateral absence of the vas deferens (CBAVD) in men, contributing to infertility.
- Prevalence: Approximately 1 in 2,500 to 3,500 newborns of European ancestry, the most common lethal genetic disorder in this population.
Sickle Cell Anemia
- Result of mutation in the HBB gene, leading to abnormal hemoglobin S.
- Symptoms typically appear in early childhood.
- Clinical manifestations include:
- Anemia due to sickled cells' premature destruction.
- Increased susceptibility to infections.
- Pain episodes from sickled cells obstructing blood vessels.
- Jaundice from red blood cell breakdown.
- Pulmonary hypertension occurs in approximately one-third of affected adults.
- Severity of symptoms varies widely among individuals.
Phenylketonuria (PKU)
- Caused by mutations in the PAH gene responsible for producing phenylalanine hydroxylase.
- Clinical presentations range from mild (variant PKU) to severe (classic PKU).
- Infants appear normal initially; untreated classic PKU can lead to severe intellectual disability.
- Additional symptoms may include seizures, developmental delays, behavioral issues, and a musty odor due to excess phenylalanine.
- Increased risk of developmental issues in infants born to mothers with untreated PKU.
- Prevalence: Occurs in about 1 in 10,000 to 15,000 newborns, usually detected through newborn screening.
Tay-Sachs Disease
- Caused by mutations in the HEXA gene affecting the enzyme beta-hexosaminidase A.
- Enzyme crucial for breaking down GM2 ganglioside, leading to accumulation and neuron destruction.
- Clinical presentations:
- Initial normal development followed by motor skill loss, beginning at 3-6 months.
- Symptoms include exaggerated startle reactions, seizures, vision and hearing loss, and progressive paralysis.
- Characteristic eye abnormality: cherry-red spot.
- Typically results in early childhood death.
- More common in individuals of Ashkenazi Jewish heritage, certain French-Canadian communities, Amish communities, and the Cajun population.
Xeroderma Pigmentosum (XP)
- Caused by mutations in multiple genes involved in DNA repair, particularly nucleotide excision repair (NER).
- About half of U.S. cases involve mutations in the XPC, ERCC2, and POLH genes.
- Clinical manifestation includes severe sunburn after minimal sun exposure.
- Increased risk of skin cancers and other skin-related symptoms due to poor DNA repair mechanisms.
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Description
This quiz explores the genetic basis of cystic fibrosis, focusing on mutations in the CFTR gene. It covers the impact on chloride channels and how these mutations affect various bodily systems. You will also learn about the clinical presentation and the factors influencing the condition's severity.
