Genetic Disorders: Inheritance Patterns

Questions and Answers

Which of the following is an example of an autosomal dominant disorder?

Thalassemia

Cystic fibrosis

Huntington Disease (correct)

Hemophilia A

Which disorder is associated with autosomal recessive inheritance?

Phenylketonuria (correct)

Duchenne muscular dystrophy

Marfan syndrome

Fragile X syndrome

Which of the following is a characteristic of X-linked recessive disorders?

Daughters of affected males will always be carriers. (correct)

Females usually express the disorder fully.

Affected males can transmit the disorder to their sons.

Males have two X chromosomes.

What is the cause of Tay-Sachs Disease?

Deficiency of hexosaminidase A Signup and view all the answers

What genetic change is associated with Fragile X syndrome?

[CGG] repeat expansion Signup and view all the answers

Males with X-linked recessive disorders inherit a second X chromosome from their fathers.

False Signup and view all the answers

Patients with _____ syndrome often present with cognitive impairment and aggression.

Fragile X Signup and view all the answers

Match the following genetic disorders with their inheritance patterns:

Huntington Disease = Autosomal Dominant Cystic fibrosis = Autosomal Recessive Hemophilia = X-linked Recessive Tay-Sachs Disease = Autosomal Recessive Signup and view all the answers

Which genetic disorder is a result of trisomy 21?

Down Syndrome Signup and view all the answers

Marfan Syndrome is caused by a deficiency in FBN1.

True Signup and view all the answers

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.

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.