Genetics Mendelian Disorders Quiz

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Questions and Answers

What type of chromosomal abnormality results from a portion of a chromosome being missing?

Translocation

Inversion

Deletion (correct)

Duplication

Which chromosomal abnormality is commonly associated with a karyotype of 47, XXY?

Turner syndrome

Edwards syndrome

Klinefelter syndrome (correct)

Down syndrome

What chromosomal abnormality is most likely to lead to spontaneous abortion during the first trimester?

Aneuploidy (correct)

Normal karyotype

Sex chromosome imbalances

Balanced translocation

What physical feature is NOT commonly associated with Turner syndrome?

Epicanthic folds Signup and view all the answers

Which method has the advantage of providing a global strategy for viewing the chromosomal complement but suffers from low resolution?

Karyotype Signup and view all the answers

What advantage does comparative genomic hybridization offer for genetic analysis?

Utilization of fresh or fixed tissue samples Signup and view all the answers

Which of the following is NOT a disadvantage of the Polymerase Chain Reaction (PCR)?

Requires a large amount of patient sample Signup and view all the answers

Which indication for genetic analysis relates to the mother’s age?

Mother of advanced age (>34 years) Signup and view all the answers

What is a limitation of comparative genomic hybridization?

Must know suspected abnormalities Signup and view all the answers

What method does RT-PCR use to amplify genetic material?

RNA conversion to DNA followed by amplification Signup and view all the answers

What is the most common mutation associated with cystic fibrosis?

A three-base deletion of codon 508 Signup and view all the answers

Which organ is primarily affected by excessive NaCl excretion in cystic fibrosis?

Skin Signup and view all the answers

What is the likelihood of a son being affected if his mother is a carrier of an X-linked recessive disorder?

50% Signup and view all the answers

Which of the following conditions is NOT classified as an autosomal recessive disease?

Duchenne muscular dystrophy Signup and view all the answers

In X-linked recessive inheritance, what can be concluded about the daughters of an affected male?

They are carriers of the disorder. Signup and view all the answers

What is a classic symptom of pancreatic involvement in cystic fibrosis?

Malabsorption Signup and view all the answers

What is the inheritance pattern of almost all X-linked disorders?

X-linked recessive Signup and view all the answers

Which of the following statements about men and X-linked conditions is correct?

Men are hemizygous for the X chromosome. Signup and view all the answers

What is the inheritance pattern of Fragile X syndrome?

X-linked recessive Signup and view all the answers

What is the commonly observed physical phenotype in males with Fragile X syndrome?

Large mandible and macroorchidism Signup and view all the answers

Which chromosomal abnormality is associated with Turner syndrome?

Aneuploidy with a single X chromosome Signup and view all the answers

What is the effect of an expansion of trinucleotides in the FMR1 gene?

Leads to Fragile X syndrome Signup and view all the answers

How are mitochondrial disorders typically inherited?

Maternally inherited Signup and view all the answers

Which of the following represents an example of aneuploidy?

45, X0 Signup and view all the answers

Among the following, which disorder is primarily associated with severe bleeding due to issues with clotting factors?

Hemophilia A and B Signup and view all the answers

What is defined as a multiple of the haploid (n) number of chromosomes?

Euploid Signup and view all the answers

In autosomal dominant disorders, what is true about the inheritance pattern?

One affected parent can transmit the condition to their offspring. Signup and view all the answers

Which of the following disorders is categorized as an autosomal dominant disorder?

Huntington’s Disease Signup and view all the answers

What is the likelihood of an offspring being affected by an autosomal dominant disorder if one parent is affected and the other is not?

50% Signup and view all the answers

What characterizes autosomal recessive disorders in terms of allele mutation?

Both alleles must be mutated for the disease to manifest. Signup and view all the answers

What is a common cause of autosomal recessive disorders?

Defects in enzymes involved in metabolic pathways. Signup and view all the answers

Which of the following statements about Marfan's syndrome is true?

It can lead to sudden death due to aortic dissection. Signup and view all the answers

In the context of cystic fibrosis, what is the genetic inheritance pattern?

Autosomal recessive. Signup and view all the answers

Study Notes

Transmission Patterns of Single-Gene Disorders

Follow Mendelian rules, categorized as autosomal dominant, autosomal recessive, or X-linked disorders.

Autosomal Dominant Disorders

Manifested in heterozygous state, only one mutant allele required for disease expression.
Typically involves structural proteins; affected individuals can transmit the condition.
Equal incidence in males and females; 50% probability of offspring being affected.
Examples include:
- Huntington’s Disease: Neurological disorder.
- Neurofibromatosis: Tumors on nerve tissue.
- Marfan Syndrome: Fibrillin defect leading to aortic dissection.
- Familial Hypercholesterolemia: Elevated cholesterol levels.

Autosomal Recessive Disorders

Largest category of Mendelian disorders, requiring both alleles to be mutated for phenotype expression.
Mostly linked to metabolic errors.
25% chance offspring will inherit the disorder if both parents are carriers.
Examples include:
- Cystic Fibrosis: Caused by mutations in CFTR, leading to severe respiratory and digestive issues.
- Phenylketonuria (PKU): Metabolic disorder affecting amino acid breakdown.
- Sickle Cell Disease: Hematopoietic disorder affecting red blood cell shape.

X-Linked Disorders

Mostly recessive; affect males more due to hemizygosity for the X chromosome.
Affected males do not pass the condition to their sons, but all daughters become carriers.
Common disorders include:
- Duchenne Muscular Dystrophy: Progressive muscle degeneration.
- Hemophilia A and B: Blood clotting disorders.
- Fragile X Syndrome: Leading cause of familial intellectual disability, involves CGG repeat expansion.

Mitochondrial Disorders

Maternal inheritance; diseases are passed down from affected mothers to all children.
Example: Leber Hereditary Optic Neuropathy.

Chromosomal Abnormalities

Common in live births (1 in 200) and miscarriages (50% of first-trimester losses).
Can be numerical (aneuploidy) or structural (deletions, translocations).
Down Syndrome: Most common aneuploidy caused by Trisomy 21, characterized by mental retardation and physical anomalies.
Turner Syndrome: Affects females, often resulting from monosomy X, associated with short stature and infertility.

Diagnosis of Genetic Diseases

Karyotype: Identifies overall chromosome structure but has low resolution.
Fluorescence In Situ Hybridization (FISH): High resolution, used for specific abnormalities.
Comparative Genomic Hybridization: Identifies chromosomal differences, may miss subtle changes.
Molecular Diagnosis: Utilizes techniques like PCR to detect nucleotide-level mutations.

Indications for Genetic Analysis

Prenatal Analysis: Age of mother, known carrier status, previous chromosomal anomalies.
Postnatal Analysis: Unexplained mental retardation, infertility, and multiple congenital anomalies.

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Description

Test your knowledge on the transmission patterns of single-gene disorders, with a focus on Mendelian inheritance rules. This quiz covers autosomal dominant, autosomal recessive, and X-linked disorders, ensuring a comprehensive understanding of genetic conditions.