Inherited diseases Flashcards
What type of inheritance pattern does cystic fibrosis follow?
Autosomal recessive.
What gene is mutated in cystic fibrosis, and what protein does it encode?
The CFTR gene on chromosome 7 encodes the CF transmembrane conductance regulator protein, which is involved in ion transport.
What are the main clinical features of cystic fibrosis?
Accumulation of mucus, recurrent infections (e.g., Pseudomonas aeruginosa), and excessive inflammation in the lungs.
Why is DNA testing performed for cystic fibrosis?
To confirm diagnosis, determine prognosis, perform prenatal testing, identify at-risk family members, and for newborn screening.
What is the inheritance pattern of hereditary hemochromatosis?
Autosomal recessive.
What gene is associated with hereditary hemochromatosis?
The HFE gene on chromosome 6.
What is the primary characteristic of hereditary hemochromatosis?
Deposition of iron in tissues, leading to organ damage.
What tests are performed after confirming HFE gene mutations?
Transferrin saturation, serum ferritin, and DNA testing of at-risk family members.
What is the inheritance pattern of CPS I deficiency?
Autosomal recessive.
What is the role of CPS I in the urea cycle?
It catalyzes the first step of the urea cycle, converting ammonia into carbamoyl phosphate.
What is the consequence of CPS I deficiency?
Accumulation of ammonia, which can lead to coma and death.
How is DNA testing performed for CPS I deficiency?
Indirect testing using linkage studies to track the disease gene through a family.
What is the inheritance pattern of achondroplasia?
Autosomal dominant.
What gene is mutated in achondroplasia?
The FGFR3 gene on chromosome 4, which encodes the fibroblast growth factor receptor 3 protein.
Why is prenatal testing performed for achondroplasia?
To confirm the diagnosis of achondroplasia in the fetus.
What is the inheritance pattern of Huntington disease?
Autosomal dominant.
What is the molecular basis of Huntington disease?
An increase in the number of CAG repeats in the HD gene on chromosome 4.
How is DNA testing performed for Huntington disease?
PCR is used to determine the exact number of CAG repeats.
What causes Down syndrome?
An extra copy of chromosome 21 (trisomy 21).
What are the clinical features of Down syndrome?
Distinct facial appearance, intellectual disability, developmental delays, and possible thyroid or heart disease.
How is Down syndrome diagnosed prenatally?
Through amniotic fluid or chorionic villus sampling.
What causes Patau syndrome?
An extra copy of chromosome 13 due to nondisjunction.
What are the clinical features of Patau syndrome?
Severe intellectual disability, heart defects, brain or spinal cord abnormalities, and cleft lip/palate.
What causes Edwards syndrome?
An extra copy of chromosome 18.
What are the clinical features of Edwards syndrome?
Cleft palate, clenched fists, heart defects, and deformed feet.
What causes Triple X syndrome?
An extra X chromosome in females due to an error in embryo development.
What are the clinical features of Triple X syndrome?
Learning disabilities, delayed speech and motor skills, weak muscle tone, and behavioral difficulties.
What causes Klinefelter syndrome?
An extra X chromosome in males (47,XXY).
What are the clinical features of Klinefelter syndrome?
Small testes, reduced testosterone, low sperm count, and infertility.
What causes Turner syndrome?
Missing or incomplete sex chromosome (45,X).
What are the clinical features of Turner syndrome?
Short stature, loss of ovarian function, and infertility.
What is the inheritance pattern of hemophilia A?
X-linked recessive.
What gene is mutated in hemophilia A?
The F8 gene, which encodes coagulation factor VIII.
What is the inheritance pattern of Duchenne muscular dystrophy (DMD)?
X-linked recessive.
What gene is mutated in DMD?
The dystrophin gene.
What are examples of mitochondrial diseases?
Leber hereditary optic neuropathy and Leigh syndrome.
What are examples of complex diseases?
Thrombophilia, inherited breast cancer, and inherited colon cancer.
Why is linkage analysis used in CPS I deficiency?
To track the disease gene through a family when direct mutation testing is not available.
How does an extra chromosome 21 lead to Down syndrome?
The extra genetic material disrupts normal development, leading to intellectual disability and physical abnormalities.
Why are males more affected by X-linked recessive disorders than females?
Males have only one X chromosome, so a single mutation can cause the disease. Females have two X chromosomes and need two mutations to be affected.
