Genetics and Genetic Disorders Quiz

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Questions and Answers

What is the primary result of X chromosome inactivation in females?

In females, one X chromosome remains active while the other is randomly inactivated, resulting in the formation of a Barr body.

What are mutations and how do they differ from polymorphisms?

Mutations are changes in DNA sequences that can lead to disease, while polymorphisms are benign genetic variations that do not cause disease.

What role does DNA methylation play in gene expression?

DNA methylation usually down-regulates RNA transcription, thereby affecting gene expression.

Explain the significance of genomic imprinting.

Genomic imprinting selectively inactivates certain chromosomal regions, impacting gene expression based on parental origin. Signup and view all the answers

What are chromosomal abnormalities, and how can they be detected?

Chromosomal abnormalities, such as aneuploidy and polyploidy, can be detected through karyotyping, ploidy analysis, and FISH. Signup and view all the answers

What are the consequences of aneuploidy in humans?

Aneuploidy can lead to significant developmental issues and is associated with conditions like Down syndrome. Signup and view all the answers

Describe the differences between polyploidy and aneuploidy.

Polyploidy involves having more than two of any autosome, while aneuploidy refers to gains or losses of individual chromosomes. Signup and view all the answers

How do epigenetic alterations differ from mutations?

Epigenetic alterations do not change the DNA sequence itself but affect gene expression through modifications like DNA methylation. Signup and view all the answers

What genetic abnormality is associated with DiGeorge syndrome?

del(22q) Signup and view all the answers

Identify one clinical feature of Cri du chat syndrome.

Catlike cry in infancy Signup and view all the answers

What is the incidence rate of Wilms’ tumor associated with contiguous gene syndrome?

1/15,000 live births Signup and view all the answers

Define the term 'pedigree' in the context of genetic diseases.

A pedigree is a diagram that shows the transmission pattern of genetic traits in a family. Signup and view all the answers

How do heterozygous individuals express their phenotype in an autosomal-dominant transmission pattern?

They express the affected phenotype. Signup and view all the answers

What is one of the clinical features associated with contiguous gene syndrome?

Aniridia (absence of iris) Signup and view all the answers

What is the significance of the 148 bp PCR product in relation to mutation detection?

The 148 bp PCR product indicates the presence of a specific mutation. Signup and view all the answers

Explain the significance of codominance in the context of genetics.

Codominance means that both parental phenotypes are expressed simultaneously in the offspring. Signup and view all the answers

What does the absence of a trait in a pedigree indicate?

It is indicated by open symbols with no coloring. Signup and view all the answers

How does a primer designed shorter than the normal product aid in mutation analysis?

It amplifies a distinct, shorter 123-bp normal product, allowing for differentiation from the mutant product. Signup and view all the answers

What type of genetic polymorphism is associated with deficiencies in folate metabolism?

The 677C>T (p.A222V) and 1298 A>C (p.E429A) polymorphisms are linked to these deficiencies. Signup and view all the answers

Explain the role of MnlI restriction enzyme in analyzing the factor V Leiden mutation.

MnlI digestion of the DNA will yield different fragment patterns in normal versus mutated DNA. Signup and view all the answers

What automated systems have been developed for monitoring clot formation?

Automated systems that measure changes in light transmittance during clot formation have been developed. Signup and view all the answers

Describe the health consequences of hemochromatosis.

Hemochromatosis leads to iron overabsorption, causing damage to the pancreas, liver, skin, and increases the risk of heart disease and diabetes. Signup and view all the answers

What is the purpose of sequencing factors IX and XIII in coagulation analysis?

Sequencing these factors helps identify the genetic causes of abnormal coagulation. Signup and view all the answers

What techniques aside from PCR are used for detecting genetic variants?

Multiplex qPCR and high-resolution melt-curve methods are also used for detecting genetic variants. Signup and view all the answers

What distinguishes mitochondrial mutations from other genetic disorders in terms of inheritance?

Mitochondrial mutations display maternal inheritance, while the disorders described have autosomal patterns of inheritance. Signup and view all the answers

List two clinical tests that are important for diagnosing mitochondrial disorders.

Electroencephalography and neuroimaging are two important clinical tests for diagnosing mitochondrial disorders. Signup and view all the answers

What are high blood or cerebrospinal fluid lactate concentrations indicative of in mitochondrial diseases?

They indicate a potential issue with mitochondrial function, as these elevations are observed in certain mitochondrial diseases. Signup and view all the answers

Describe what short tandem repeats (STRs) are and their relevance in nucleotide-repeat expansion disorders.

STRs are sequences of 1 to 10-bp repeating units, and their expansions or contractions during DNA replication can lead to nucleotide-repeat expansion disorders. Signup and view all the answers

What percentage of patients with CCHS are estimated to have the PHOX2b gene mutation?

62% to 98% Signup and view all the answers

What is the significance of the CGG expansion in fragile X syndrome?

The CGG expansion in fragile X syndrome is associated with the FMR-1 gene and becomes larger than 2,000 repeats in full fragile X syndrome. Signup and view all the answers

In fragile X syndrome, what happens to the expansion of CGG repeats?

The expansion typically becomes so large that it is microscopically visible. Signup and view all the answers

What syndrome is caused by a deletion on the paternal chromosome 15?

Prader–Willi syndrome Signup and view all the answers

What are the primary symptoms of Angelman syndrome?

Ataxia, seizures, and inappropriate laughter Signup and view all the answers

Mention a direct test that is specific for mitochondrial dysfunction.

Histological examination of muscle biopsies is a direct test specific for mitochondrial dysfunction. Signup and view all the answers

How can high blood glucose levels be relevant in diagnosing mitochondrial diseases?

High blood glucose levels can be observed in patients with certain mitochondrial diseases, indicating impaired cellular energy metabolism. Signup and view all the answers

What is genomic imprinting?

Genomic imprinting is transcriptional silencing through histone or DNA modification. Signup and view all the answers

What is the mechanism of expansion mutations in amyotrophic lateral sclerosis (ALS)?

Expansion of a hexanucleotide repeat unit Signup and view all the answers

How can translocations and certain deletions be detected?

By standard karyotyping Signup and view all the answers

What type of disorders does Huntington disease belong to?

Polyglutamine expansion disorders Signup and view all the answers

What two methods can detect smaller deletions beyond standard karyotyping?

High-resolution karyotyping and cytogenetic methods Signup and view all the answers

What type of disorders are exemplified by nonpolyglutamine expansions according to the passage?

Nonpolyglutamine expansion disorders. Signup and view all the answers

Which gene is associated with Fragile X syndrome as mentioned in the table?

Fragile X mental retardation 2 (Xq28). Signup and view all the answers

What is the normal repeat range for the gene associated with Friedreich ataxia?

7–34 repeats. Signup and view all the answers

What common methodology is used for detecting genetic disorders involving repeat expansions in the context described?

PCR or RFLP analysis. Signup and view all the answers

How does the repeat size for Myotonic dystrophy compare to the symptomatic range?

Normal is 5–37 repeats, symptomatic is over 50. Signup and view all the answers

What type of genetic modification is highlighted as important in imprinting and can affect diagnosis of disorders?

DNA methylation. Signup and view all the answers

Identify one disorder listed that causes changes due to an expansion of CTG repeats.

Myotonic dystrophy or spinocerebellar ataxia type 8. Signup and view all the answers

What role does Southern blotting play in the context of the information provided?

It aids in detecting methylation-specific patterns. Signup and view all the answers

Study Notes

Molecular Detection of Inherited Diseases

Mendelian Inheritance: Patterns of inheritance exhibited by family pedigrees are described.
Chromosome Abnormalities: Abnormalities in chromosome number (e.g., polyploidy, aneuploidy) and structure (e.g., translocations, inversions, deletions) are illustrated.
Penetrance and Variable Expressivity: These terms are defined in the context of disease phenotypes.
Single-gene Disorders and Affected Genes: Disease syndromes are related to affected genes.
Single-gene Disorder Detection Methods: Examples of laboratory methods used to detect single-gene disorders are provided.
Non-Mendelian Inheritance: Non-Mendelian inheritance patterns, such as mitochondrial disorders and nucleotide-repeat expansion diseases, are discussed.
Genomic Imprinting's Effect on Disease: Genomic imprinting's impact on disease phenotype is explored.

Molecular Basis of Inherited Diseases

Mutations: Changes in DNA nucleotide sequences (point mutations, chromosomal mutations) are described.
Polymorphisms: Proportionately represented genotypes in a population are defined. Benign polymorphisms are useful for mapping disease genes and determining parentage.
Epigenetic Alterations: Alterations in gene expression without changing the primary DNA sequence (e.g., DNA methylation, genomic imprinting, chromatin remodeling).
Mutations in Germ Cells vs Somatic Cells: Mutations in germ cells result in inherited diseases; mutations in somatic cells can cause cancer and some congenital malformations.
Congenital Disorders: These are present at birth but not necessarily inheritable.
Molecular Basis of Specific Diseases: Specific examples of single-gene disorders (e.g., lysosomal storage diseases, factor V leiden, prothrombin) are included.

Advanced Concepts

Lyon Hypothesis: Female mammals inactivate one X chromosome at random during embryonic development.
Chromosomal Abnormalities: Examples of diseases with different chromosomal abnormalities (e.g., Down syndrome, Edwards syndrome, Patau syndrome) are provided. Incidence rates and clinical features are included.
Patterns of Inheritance within Single Gene Disorders: Autosomal dominant, autosomal recessive, and X-linked (sex-linked) recessive inheritance patterns are described and illustrated with pedigrees.
Genomic Imprinting: This describes the selective inactivation of specific chromosomal regions that impact specific disease phenotypes.
Mosaicism: The presence of two or more genetically different cell populations in a single organism is described.
Autosomal Recessive Disorders: Characteristics of such disorders and their detection are described.
Mitochondrial Mutations: A description of inheritance through the maternal line and examples of mitochondrial disorders are included.
Nucleotide Repeat Expansion Disorders: Examples like fragile X syndrome and Huntington disease, where triplet-repeat expansion is responsible for disease phenotype, are noted.

Techniques in the Clinical Laboratory

Molecular Testing Methods: Examples of molecular methods used to detect genetic mutations are included (e.g., PCR-RFLP, Sequencing).
Types of diseases associated with genome/chromosome Mutations: Specific disorders mentioned.
Clinical Features & Prevalence of disorders Clinical observations and incidence in different populations.
Cytochrome P-450 Enzymes: Function, effects of drugs, and polymorphisms in this protein system are detailed.
Single-Gene Disorder Methods: Different methods to detect gene mutations in single-gene disorders.
Single-Gene Disorders with Non-Classical Inheritance: Description of mitochondrial disorders, genomic imprinting, gonadal mosaicism, and their molecular testing.
Multifactoral Inheritance: Complex diseases resulting from interactions of multiple genes and environmental factors are described.
Limitations of Molecular Testing: Factors impacting molecular testing's usefulness in diagnosing some disorders are highlighted.

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Description

Test your knowledge on key concepts in genetics, including X chromosome inactivation, mutations, and chromosomal abnormalities. This quiz covers essential topics related to gene expression and clinical features of various genetic disorders. Perfect for students studying genetics or related fields!