Cytogenetics Quiz: Karyotype and FISH Techniques

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Questions and Answers

What is the purpose of adding a hypotonic solution during the harvesting phase?

To stimulate mitosis

To enhance cell growth

To cause cell to burst for visualization (correct)

To fix the cells for analysis

Which technique is used to stop mitosis during the harvesting phase?

Using hypotonic solutions

Staining

Mitosis enhancement

Spindle inhibitor application (correct)

What does FISH primarily detect?

Visible mutations through conventional techniques

Small deletions and duplications (correct)

Entire chromosomal abnormalities

Polyploidy conditions

In the context of chromosomes, what does aneuploidy refer to?

The gain or loss of one or more chromosomes Signup and view all the answers

Which staining technique is commonly used during the analysis phase?

Giemsa staining Signup and view all the answers

What is required for the hybridization process in FISH?

Denatured single-stranded DNA Signup and view all the answers

What is a characteristic feature of polyploidy?

More than 2 haploid chromosome sets Signup and view all the answers

During the sample analysis phase, how many cells are typically analyzed?

10-20 cells Signup and view all the answers

What characterizes a nonsense mutation?

It creates a stop codon instead of an amino acid. Signup and view all the answers

How do frameshift mutations typically affect protein function?

They cause possible introduction of stop codons. Signup and view all the answers

What is the consequence of an insertion or deletion that is not a multiple of three?

It results in a frameshift mutation. Signup and view all the answers

What is the 'GT-AG' rule related to?

It pertains to the nucleotides involved in RNA splicing. Signup and view all the answers

What is a common consequence of splice site mutations?

They induce the skipping of exons. Signup and view all the answers

What happens during nonsense mediated decay?

Mutated mRNA is degraded before translation. Signup and view all the answers

What mutation type is likely to have a more severe outcome in terms of protein folding?

Frameshift mutations. Signup and view all the answers

How do translocations impact gene structure?

They disrupt normal gene arrangement and function. Signup and view all the answers

What is the primary characteristic of multifactorial inheritance?

It can result from environmental factors and several genetic variants. Signup and view all the answers

What method allows for the estimation of the genetic and environmental contributions to a multifactorial trait?

Heritability studies. Signup and view all the answers

How does liability shift affect the risk of disease in families?

It increases with each affected family member and the severity of their disease. Signup and view all the answers

What distinguishes polygenic inheritance from Mendelian inheritance?

Polygenic inheritance results from variants in many genes. Signup and view all the answers

In what scenario can exact recurrence rates be calculated?

For Mendelian inheritance. Signup and view all the answers

Which factor is NOT considered in assessing familial risk for multifactorial diseases?

Mutation in a single gene. Signup and view all the answers

What does a high level of concordance in monozygotic twins suggest in studies of disease?

A larger genetic component is likely involved. Signup and view all the answers

Which combination of factors contributes to relative risk in multifactorial inheritance?

Environmental and genetic factors together. Signup and view all the answers

What happens when a female carrier of an X-linked recessive condition has a son?

The son has a 50% chance of inheriting the condition. Signup and view all the answers

Which of the following best describes the 'founder effect'?

Low genetic variation due to a small group establishing a new population. Signup and view all the answers

In which population is cystic fibrosis most commonly found?

Caucasians of Northern European heritage. Signup and view all the answers

What characterizes a heterozygotic advantage in terms of genetics?

Heterozygous individuals have a fitness benefit due to resistance to certain diseases. Signup and view all the answers

What is a potential impact of consanguinity on genetic disorders?

It raises the risk of recessive genetic disorders. Signup and view all the answers

Which statement best describes Rett Syndrome?

It leads to early developmental normality followed by a regression in motor functions. Signup and view all the answers

What is a primary feature of Duchenne Muscular Dystrophy (DMD)?

Progressive muscle weakness primarily starting in the legs and pelvis. Signup and view all the answers

What is the term for the proportion of a population that carries a disease-causing allele and expresses the disease phenotype?

Penetrance. Signup and view all the answers

Which condition involves deficiency in clotting factors and is predominantly seen in males?

Haemophilia. Signup and view all the answers

What is the main consequence of reduced penetrance in genetic disorders?

Some individuals carry the mutation but do not develop the disorder. Signup and view all the answers

What does pharmacogenomics primarily study?

The interaction between genetic makeup and drug response Signup and view all the answers

What is a key aim of pharmacogenomics?

To ensure maximum efficacy with minimal adverse effects Signup and view all the answers

Which gene is responsible for the metabolism of warfarin?

CYP2C9 Signup and view all the answers

In which scenario might pharmacogenomic testing be most beneficial?

For individuals experiencing adverse drug reactions Signup and view all the answers

What does 'ultra-rapid metabolizers' refer to in pharmacogenomics?

Patients who metabolize drugs too quickly for effectiveness Signup and view all the answers

What is the significance of the term 'haplotype' in the context of pharmacogenomics?

It is a group of variants inherited together from one parent Signup and view all the answers

What is one of the major hurdles in implementing pharmacogenomic testing?

Resistance from pharmaceutical companies to provide access Signup and view all the answers

Which of the following is a common characteristic of direct-to-consumer genetic testing?

Freely available to the public without a doctor's approval Signup and view all the answers

What role does CYP 450 play in drug metabolism?

It metabolizes a majority of prescribed medications Signup and view all the answers

What does the term 'precision medicine' refer to?

Medical care personalized for individual patients Signup and view all the answers

Study Notes

Cytogenetics

Karyotype analysis: process of examining chromosomes to assess their number and structure.
Steps involved in karyotype analysis:
- Culture: Sample collection from blood, bone marrow, or amniotic fluid; incubation of cells in a sterile environment with growth medium to stimulate mitosis.
- Harvest: Stop mitosis in metaphase using mitotic arrest agents (spindle inhibitors); hypotonic solution treatment to cause cell bursting and metaphase spread; fixation to kill cells and remove debris.
- Analyze: Slide preparation; different stain techniques (Giemsa, C banding, G banding) for analysis.
Karyogram: visual representation of chromosomes arranged by size and banding pattern, analyzed microscopically.
International System for Human Cytogenetic Nomenclature (ISCN): a standardized system for describing chromosome abnormalities.

FISH (Fluorescent In-Situ Hybridization)

Detects subtle changes in DNA sequences like deletions, duplications, rearrangements, and identifies the origin of chromosomal material.
Utilizes fluorescently labelled probes that bind to specific DNA sequences.
Steps involved:
- Denaturation: Separation of DNA into single strands using heat and chemicals.
- Probe: Application of probes designed for specific DNA sequences.
- Hybridization: Binding of probes to complementary sequences on chromosomes.
- Analyze: Visualization under a fluorescent microscope.
Advantages: higher resolution, higher sensitivity, but limited number of probes.

Numerical Chromosome Abnormalities

Polyploidy: Presence of more than two sets of chromosomes (e.g., triploidy with 3 haploid sets).
Aneuploidy: Gain or loss of one or more chromosomes (e.g., trisomy with 46+1 chromosomes).

Mutations

Point mutations: changes in a single nucleotide.
- Nonsense: Introduces a stop codon, leading to truncated or non-functional proteins.
- Missense: Alters an amino acid, potentially impacting protein function.
Insertions/deletions (Indels):
- In-frame mutations: occur in multiples of three nucleotides, maintaining the reading frame and potentially resulting in milder effects.
- Frameshift mutations: occur when insertions or deletions are not in multiples of three, disrupting the reading frame and causing significant protein alterations.
Splice site mutations: mutations in sequences that mark the boundaries between exons and introns, leading to incorrect splicing and altered protein production.

Mutation Nomenclature

Standardized system for describing mutations for easier comparison and communication.
c. refers to coding DNA sequence.
g. refers to genomic DNA sequence.
p. refers to protein sequence.
m. refers to mitochondrial DNA.

X-linked Inheritance

X-linked recessive: Mutations on an X chromosome.
- Females may be carriers and exhibit mild symptoms.
- Affected males do not have a compensating allele, so they are affected.
X-linked dominant: Rare mode of inheritance.
- Affected males may not survive due to severity of the disorder.

Population Specific Genetic Conditions

Founder effect: Occurs in populations established by a small number of individuals, leading to increased prevalence of specific alleles due to inbreeding.
Heterozygote advantage: Heterozygous genotype has higher fitness than either homozygous genotype.
Consanguinity: Marriage between closely related individuals, increasing the risk of homozygous recessive disorders.
African populations: Examples include albinism.
Caucasian populations: Examples include cystic fibrosis.
Ashkenazi Jewish populations: Examples include Tay-Sachs disease.
Afrikaner populations: Examples include sclerosteosis.
Indian populations: Examples include thalassemia.

Genetic Testing

Includes carrier screening, prenatal genetic diagnosis, prenatal genetic testing, and predictive testing.

Unusual Genetic Phenomena

Penetrance: Proportion of individuals carrying a disease-causing mutation who express the phenotype.
- Complete penetrance: All carriers with the mutation develop the disorder.
- Reduced/Incomplete penetrance: Some carriers do not develop the disorder, influenced by other genetic and environmental factors.
Liability shift: Chance of developing a disease is modified by family history.
Recurrence vs. relative risks: Punnett squares predict recurrence risks for Mendelian disorders, but for multifactorial conditions, relative risks based on family history and environmental factors are used.

Heritability Studies

Estimate the relative contributions of genetics and environment to multifactorial traits.
Population/migration studies: Compare disease prevalence in different populations to identify genetic and environmental influences.
Family studies: Examine whether a disease occurs at a higher frequency in families compared to the general population.
Twin studies: Compare concordance rates between monozygotic and dizygotic twins to assess the role of genetics.
Tag SNP: Single nucleotide polymorphisms (SNPs) located near a disease-associated gene are used as markers in association studies.

Direct-to-Consumer Genetic Testing

Freely available genetic testing services offered directly to consumers without the involvement of healthcare providers.

Pharmacogenomics

Study of how genetic variations affect individuals' responses to medications.
Pharmacogenetics: Focuses on the effect of one gene on drug response.
Haplotype: A group of variants inherited together from one parent on a chromosome.
ADME: Absorption, distribution, metabolism, and excretion of drugs.
CYP450: Cytochrome P450 enzyme superfamily responsible for metabolizing many drugs.
Aim: To optimize drug efficacy and minimize adverse effects by tailoring treatments to individuals' genetic profiles.

Precision Medicine

Tailoring medical care using genetic and molecular profiling to optimize outcomes for individuals or specific patient groups.

Precision Public Health

Tailoring healthcare interventions to specific population groups based on their genetic and environmental characteristics.

Challenges in Implementing Pharmacogenomics

Limited availability of personalized medicine alternatives, disincentives to make other drugs available, and insufficient education of healthcare providers.

Pharmacogenetics in Clinical Practice

Examples include genetic testing for variants affecting response to warfarin, codeine, and statins.

Pharmacogenetics in Africa

Challenges include high disease burden, limited resources, and political instability, as well as the need for more research on genetic diversity.

Prenatal Investigations

Investigations conducted during pregnancy to detect abnormalities in fetal development and offer options for termination if necessary.

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Description

Test your knowledge on cytogenetics focusing on karyotype analysis and the FISH technique. This quiz covers the processes of sample culture, harvesting, and chromosome analysis. Dive into the essential aspects of karyograms and chromosomal nomenclature.