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Questions and Answers
Which of the following is an example of an autosomal dominant disorder?
Which of the following is an example of an autosomal dominant disorder?
Which disorder is associated with autosomal recessive inheritance?
Which disorder is associated with autosomal recessive inheritance?
Which of the following is a characteristic of X-linked recessive disorders?
Which of the following is a characteristic of X-linked recessive disorders?
What is the cause of Tay-Sachs Disease?
What is the cause of Tay-Sachs Disease?
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What genetic change is associated with Fragile X syndrome?
What genetic change is associated with Fragile X syndrome?
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Males with X-linked recessive disorders inherit a second X chromosome from their fathers.
Males with X-linked recessive disorders inherit a second X chromosome from their fathers.
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Patients with _____ syndrome often present with cognitive impairment and aggression.
Patients with _____ syndrome often present with cognitive impairment and aggression.
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Match the following genetic disorders with their inheritance patterns:
Match the following genetic disorders with their inheritance patterns:
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Which genetic disorder is a result of trisomy 21?
Which genetic disorder is a result of trisomy 21?
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Marfan Syndrome is caused by a deficiency in FBN1.
Marfan Syndrome is caused by a deficiency in FBN1.
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Study Notes
Inheritance Patterns of Genetic Disorders
- Autosomal Dominant: Only one parent needs to be affected; examples include Huntington Disease, Myotonic Dystrophy, Marfan Syndrome, and Ehlers-Danlos Syndrome.
- Autosomal Recessive: Both parents must carry the gene; examples include Cystic Fibrosis, Phenylketonuria (PKU), and Tay-Sachs Disease. Often occurs due to consanguineous marriages.
- X-linked Recessive: Primarily affects males as they have one X chromosome. Examples include Duchenne Muscular Dystrophy, Hemophilia, and G6PD deficiency.
Chromosomal Disorders
- Turner Syndrome: Caused by monosomy X (45X), resulting in missing one X chromosome, common in females.
- Klinefelter Syndrome: Males have an extra X chromosome (47, XXY), leading to infertility and changes in secondary sexual characteristics.
- Down Syndrome: Characterized by Trisomy 21, where individuals have three copies of chromosome 21.
- Prader-Willi Syndrome: Results from maternal uniparental disomy and deletion of chromosome region 15.
- Angelman Syndrome: Caused by paternal uniparental disomy and deletion on chromosome 15.
X-Linked Recessive Disorders
- Males are more severely affected as they have a single X chromosome; they express the disorder if they inherit a mutant gene.
- Carrier females (with two X chromosomes) often do not show the full phenotype due to compensation by the normal allele.
- Random X-chromosome inactivation in females can lead to mild symptoms if the normal X is inactivated in certain cells.
Genetic Mutations
- Trinucleotide-Repeat Mutations: Abnormal expansion of DNA sequences can lead to diseases such as Fragile X Syndrome, Myotonic Dystrophy, and Huntington Disease.
- Anticipation phenomenon shows that the number of repeats can increase in successive generations.
Specific Disorders
- Fragile X Syndrome: Caused by a CGG repeat expansion in the FMR1 gene, resulting in cognitive impairments and emotional issues.
- Myotonic Dystrophy: Characterized by a CTG repeat in the DMPK gene, which affects muscle function.
- Huntington Disease: Associated with a CAG repeat in the HTT gene, leading to neurodegeneration.
Enzyme Deficiencies
- Tay-Sachs Disease: Caused by hexosaminidase A deficiency, leading to accumulation of GM2-gangliosides and affecting the CNS.
- Marfan Syndrome: Due to mutations in the FBN1 gene, impacting connective tissue, particularly fibrillin-1.
- Familial Hypercholesterolemia: Results from mutations in the LDLR gene (85%), leading to high levels of LDL cholesterol and increased risk for atherosclerosis.
Additional Clinical Features of Fragile X Syndrome
- Presence of tremors/ataxia and primary ovarian failure.
- Cognitive impairments, including autism spectrum disorders and attention deficit hyperactivity disorder (ADHD).
- Affects males more severely due to the nature of X-linked inheritance.
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Description
Explore the various inheritance patterns associated with genetic disorders in this quiz. Understand the distinctions between autosomal dominant, autosomal recessive, and X-linked recessive traits. Test your knowledge and deepen your understanding of genetics.
