Genetic Testing Overview and Applications
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What is the main purpose of genetic testing?

  • To cure genetic disorders through medication.
  • To assess genetic variations for potential health applications. (correct)
  • To evaluate only physical traits inherited from parents.
  • To determine the exact genetic makeup of an individual.

    • Which method is used for chromosomal analysis in cytogenetics?

  • Polymerase chain reaction.
  • Molecular sequencing.
  • Karyotyping and banding. (correct)
  • Fluorescence in situ hybridization.

    • Which of the following accurately describes molecular testing?

  • It is focused solely on RNA analysis.
  • It requires previous knowledge of the gene sequence involved. (correct)
  • It assesses chromosomal abnormalities through imaging.
  • It involves analyzing protein levels in the blood.

    • What are the primary applications of molecular diagnosis?

    <p>Facilitating detection, diagnosis, and monitoring response to therapy.</p> Signup and view all the answers

    What does a karyotype represent?

    <p>The complete set of chromosomes in an individual.</p> Signup and view all the answers

    What is the primary purpose of whole exome sequencing?

    <p>To identify variations in coding regions that can influence genetic disorders.</p> Signup and view all the answers

    Why is it significant to study introns in whole genome sequencing?

    <p>Introns may influence the function of exons and contribute to genetic diseases.</p> Signup and view all the answers

    How many exons does the human genome approximately contain?

    <p>Approximately 180,000.</p> Signup and view all the answers

    What types of variants can whole exome sequencing help identify?

    <p>Base or copy variants that help assess disease risk.</p> Signup and view all the answers

    What is one of the main advantages of whole genome sequencing over whole exome sequencing?

    <p>WGS can resolve structural variations in both intronic and exonic regions.</p> Signup and view all the answers

    What is the characteristic staining difference between heterochromatin and euchromatin?

    <p>Heterochromatin is darkly stained, euchromatin is lightly stained.</p> Signup and view all the answers

    Which banding technique specifically uses the Giemsa stain?

    <p>G-banding</p> Signup and view all the answers

    What is the primary purpose of fluorescent in situ hybridization (FISH)?

    <p>To visualize specific DNA or RNA sequences on chromosomes.</p> Signup and view all the answers

    How long are the probes typically used in molecular cytogenetics?

    <p>15-50 nucleotides long.</p> Signup and view all the answers

    In situ hybridization primarily provides information about what?

    <p>The chromosomal location of a gene or cellular mRNA.</p> Signup and view all the answers

    What does the term 'karyotype' refer to?

    <p>The visual representation of an individual's chromosomes.</p> Signup and view all the answers

    What is the maximum resolution of conventional FISH on metaphase chromosomes?

    <p>Several megabases.</p> Signup and view all the answers

    Which of the following techniques is NOT categorized under molecular cytogenetics?

    <p>Karyotyping.</p> Signup and view all the answers

    What does a yellow signal indicate in SNP arrays?

    <p>Equal amounts of patient and reference DNA</p> Signup and view all the answers

    What characterizes microdeletions as detected by Array CGH?

    <p>Loss of genetic information</p> Signup and view all the answers

    Which aspect of DNA sequencing does Next Generation Sequencing (NGS) primarily focus on?

    <p>Determining nucleotide order</p> Signup and view all the answers

    What is the primary principle behind Array CGH?

    <p>Hybridization of two complementary DNA strands to detect differences</p> Signup and view all the answers

    Which statement best describes copy number aberrations (CNA)?

    <p>They involve changes in the amount of DNA present.</p> Signup and view all the answers

    What technique does Next Generation Sequencing use to assemble genomic sequences?

    <p>Fragmenting DNA and reassembling after sequencing</p> Signup and view all the answers

    What type of chromosomal imbalances can Array CGH detect that karyotyping cannot?

    <p>Very small chromosomal imbalances</p> Signup and view all the answers

    What is the significance of comparing an individual's DNA to a control sample in Array CGH?

    <p>It identifies differences indicating genetic disorders.</p> Signup and view all the answers

    What does a positive genetic test result generally indicate?

    <p>A change in a specific gene or protein was found</p> Signup and view all the answers

    What percentage of BRCA1 mutation carriers are expected to develop breast cancer by age 70?

    <p>85%</p> Signup and view all the answers

    What is an uninformative test result characterized by?

    <p>A lack of useful information</p> Signup and view all the answers

    Which aspect must patients be informed about before providing consent for genetic screening?

    <p>The potential outcomes of the genetic screening</p> Signup and view all the answers

    What is a crucial step to reduce psychological distress associated with genetic testing?

    <p>Offering counseling before and after testing</p> Signup and view all the answers

    Which of the following may NOT be an outcome of a negative genetic test result?

    <p>Confirmation that a specific mutation exists</p> Signup and view all the answers

    What can misunderstanding genetic risk contribute to?

    <p>Increased stigmatization</p> Signup and view all the answers

    What must healthcare professionals consider when interpreting genetic test results?

    <p>Family history and the type of test performed</p> Signup and view all the answers

    What is the primary purpose of polymerase chain reaction (PCR)?

    <p>To amplify specific segments of DNA</p> Signup and view all the answers

    What processes occur during the PCR cycle?

    <p>Denaturation, annealing, elongation</p> Signup and view all the answers

    What does a single-nucleotide polymorphism (SNP) refer to?

    <p>A variation in a single base pair in DNA</p> Signup and view all the answers

    How often can a SNP be found in a comparison of the same chromosome from two individuals?

    <p>Every 1000 bp</p> Signup and view all the answers

    Which of the following is NOT one of the four major genome-wide assays used for assessing SNPs?

    <p>RNA sequencing (RNA-Seq)</p> Signup and view all the answers

    What advantage does microarray technology provide?

    <p>It allows for high-resolution genome-wide screens for copy number variants</p> Signup and view all the answers

    Which method is most suitable for analyzing the entire coding region of genes?

    <p>Whole exome sequencing (WES)</p> Signup and view all the answers

    What is the main characteristic of single-nucleotide polymorphisms?

    <p>They are inherited as allelic variants</p> Signup and view all the answers

    Study Notes

    Genetic Testing Overview

    • Genetic testing assesses inherited genetic variations from parents (germline variation).
    • It has broad applications in healthcare, including predicting and managing disease risk.
    • The practice has the potential to facilitate accurate and timely diagnosis and treatment for infectious diseases.

    Application - Molecular Diagnosis

    • Molecular diagnosis involves detecting pathogenic mutations in DNA and/or RNA samples.
    • This process facilitates disease detection, diagnosis, sub-classification, prognosis, and monitoring treatment responses.

    Molecular Testing

    • Direct DNA analysis is possible only when the gene sequence is known.
    • Molecular testing offers superior methodology, particularly when a biochemical test is not available.
    • DNA testing can be done with any tissue and requires minor amounts of sample.

    Cytogenetics

    • Cytogenetics studies chromosome structure, behavior in mitosis and meiosis, and factors causing chromosomal changes.
    • It is relevant to diagnosing disease status caused by abnormal chromosome number or structure.
    • Karyotyping and banding are used for chromosomal analysis.
    • Karyotyping involves collecting all chromosome structures.
    • Chromosome banding is method of analysis that categorizes individual chromosomes.

    Chromosome Analysis - Methods and Procedures

    • Cell sources include blood cells, skin fibroblasts, amniotic cells, and chorionic villi.
    • Increasing the mitotic index (using colcemid) allows for better observation of cells in mitosis (cell division).
    • The process involves cell culture, fixation, spreading of chromosomes onto microscope slides and staining.
    • Staining helps differentiate chromosomes for analysis.
    • Banding patterns on each chromosome are unique, facilitating analysis of chromosome structure.

    Karyotype Analysis - Procedure

    • The procedure involves cell counting and analysis of the banding patterns of each chromosome in selected cells.
    • Total chromosome counts (minimum 10-15 cells; with suspicion of mosaicism, up to 30 or more) are determined.
    • Chromosome analysis involves analyzing 3-5 metaphase spreads for detailed analysis and high-quality banding.
    • Banding patterns are represented as an idiogram.

    Chromosome Banding

    • Chromosome banding is based on the presence of heterochromatin (darkly stained) and euchromatin (lightly stained).
    • Various banding techniques include G-banding, C-banding, Q-banding, R-banding, and T-banding.
    • Giemsa (G)-banding is a cytogenetic method to visualize condensed chromosomes.

    Molecular Cytogenetics

    • Molecular cytogenetics locates specific DNA sequences on chromosomes.
    • It involves higher resolution analysis of chromosomes, including target DNA sequencing, probes (often 15-50 nucleotides long, chemically synthesized) and more.
    • FISH (Fluorescent in situ Hybridization), chromosome painting, CGH (comparative genomic hybridization), molecular karyotyping and Multiplex FISH(M-FISH), Spectral Karyotyping, Array CGH are all methods.

    In Situ Hybridization (FISH)

    • FISH uses DNA or RNA probes to identify chromosomal locations of genes or cellular locations of mRNA.
    • Visualization of DNA or RNA occurs in situ (within the cell).
    • Resolution in conventional FISH on metaphase chromosomes typically results in resolution of several megabases.
    • Prometaphase chromosomes offer better resolution (1 Mb).

    Biochemical Testing

    • Biochemical genetic diseases, such as inborn errors of metabolism, disrupt metabolic pathways.
    • Diagnostics tests directly measure protein activity (enzymes), metabolite level, and protein quantity/size using tissue samples (blood, urine, amniotic fluid, cerebrospinal fluid).
    • Technologies include immunohistochemistry, gas/liquid chromatography/mass spectrometry (LC/GC/MS), and bioassays.

    Immunohistochemistry (IHC)

    • Immunohistochemistry exploits antibody-antigen interactions to detect and localize specific antigens in tissues.
    • Tissue samples are typically frozen, or formalin-fixed paraffin-embedded (FFPE).
    • Steps: pretreatment & antigen retrieval, primary antibody addition, secondary antibody application, detection reagent application, visualization.

    Molecular Testing Methods

    • PCR-based methods amplify target DNA sequences using cycles of denaturation, annealing, and elongation.
    • Amplified product analysis can involve digestion with restriction enzymes followed by gel electrophoresis.

    Types of Genetic Tests

    • Genetic testing ranges from single gene examination to whole genome analysis, selecting tests based on disease type and other factors.
    • Types include targeted single variant, single gene, gene panel, genomic sequencing, chromosomal, gene expression, and protein expression.
    • Specific examples include newborn screening, diagnostic testing, carrier testing, prenatal testing, preimplantation testing, forensic testing, and research testing.

    Single-Nucleotide Polymorphisms (SNPs)

    • SNPs are single-base-pair differences in DNA sequence between individuals.
    • They are inherited as alleles and widespread throughout genomes.
    • SNPs can be found approximately every 1000 base pairs in a comparative analysis.

    Advanced Genetic Testing

    • Array comparative genomic hybridization (aCGH) assesses single nucleotide polymorphisms (SNPs) and copy number variations.
    • SNP microarrays (array) also analyze SNPs and copy number variations.
    • Other methods like whole exome sequencing (WES), and whole genome sequencing (WGS) offer detailed analysis.

    Microarray Technology

    • Microarrays are high-resolution genome-wide screenings used for copy number variants.
    • Two different oligonucleotides are used for detecting alleles (with fluorescent dye).
    • Results can indicate deletion or duplication of DNA segments.

    Next-Generation Sequencing (NGS)

    • NGS is a massively parallel sequencing technology, determining the order of nucleotides in entire genomes or targeted DNA/RNA regions.
    • The principle involves fragmenting DNA/RNA, adding adapters, sequencing the libraries, and reassembling to form the genetic sequence.

    Whole Exome Sequencing

    • Whole exome sequencing focuses on exons (coding regions) from the entire genome.
    • Exons comprise roughly 1% of the genome.
    • This sequencing identifies variations in exon sequences, assisting in disease diagnosis or assessment of disease risk.

    Whole Genome Sequencing (WGS)

    • WGS resolves the entirety of a patient's genome's detailed nucleotide sequence.
    • It identifies variations in the genome and may provide information about regulatory functions within intronic regions.
    • Informed consent and counseling regarding implications & choices are crucial.
    • Maintaining patient confidentiality and addressing potential stigma associated with genetic test results is important.

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    Genetic Testing PDF

    Description

    Explore the essentials of genetic testing, including its role in healthcare and the various applications like molecular diagnosis. This quiz covers concepts from germline variations to cytogenetics, enhancing your understanding of disease risk management and treatment strategies.

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