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Questions and Answers
What is the main purpose of karyotyping?
What is the main purpose of karyotyping?
Fluorescence In Situ Hybridisation (FISH) can detect aneuploidies in specific cell populations.
Fluorescence In Situ Hybridisation (FISH) can detect aneuploidies in specific cell populations.
True
What process is used to arrest cells in metaphase during karyotyping?
What process is used to arrest cells in metaphase during karyotyping?
Chemical treatment that inhibits cell division.
Array Comparative Genomic Hybridisation (aCGH) measures __________ to identify unbalanced chromosomal abnormalities.
Array Comparative Genomic Hybridisation (aCGH) measures __________ to identify unbalanced chromosomal abnormalities.
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Match the advanced karyotyping techniques with their descriptions:
Match the advanced karyotyping techniques with their descriptions:
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Which of the following is NOT a step in the karyotyping process?
Which of the following is NOT a step in the karyotyping process?
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Chromosomes are fixed in a solution of acetone and ethanol before staining.
Chromosomes are fixed in a solution of acetone and ethanol before staining.
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In which phase are chromosomes most visible for analysis?
In which phase are chromosomes most visible for analysis?
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What is the most common chromosomal disorder associated with an extra copy of chromosome 21?
What is the most common chromosomal disorder associated with an extra copy of chromosome 21?
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All cases of Turner syndrome are due to the complete absence of an X chromosome.
All cases of Turner syndrome are due to the complete absence of an X chromosome.
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What are two clinical manifestations of Down syndrome?
What are two clinical manifestations of Down syndrome?
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Turner syndrome affects approximately 1 in ______ female live births.
Turner syndrome affects approximately 1 in ______ female live births.
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Match the chromosomal disorders with their key characteristics:
Match the chromosomal disorders with their key characteristics:
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What is a confirmatory diagnostic test for Down syndrome?
What is a confirmatory diagnostic test for Down syndrome?
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Name one treatment approach for Turner syndrome.
Name one treatment approach for Turner syndrome.
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What is the purpose of fluorescence in situ hybridisation in karyotyping?
What is the purpose of fluorescence in situ hybridisation in karyotyping?
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Aneuploidy refers to an abnormal number of chromosomes.
Aneuploidy refers to an abnormal number of chromosomes.
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What chromosomal abnormality is characterized by the presence of an extra chromosome?
What chromosomal abnormality is characterized by the presence of an extra chromosome?
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Turner's syndrome is an example of _____, where one X chromosome is missing.
Turner's syndrome is an example of _____, where one X chromosome is missing.
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Match the following chromosomal abnormalities with their definitions:
Match the following chromosomal abnormalities with their definitions:
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Which abnormality involves a portion of the chromosome being duplicated?
Which abnormality involves a portion of the chromosome being duplicated?
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Structural chromosomal abnormalities include only deletions and duplications.
Structural chromosomal abnormalities include only deletions and duplications.
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What type of chromosomal abnormality involves a segment of one chromosome being transferred to another?
What type of chromosomal abnormality involves a segment of one chromosome being transferred to another?
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Aneuploidy can result in conditions like ______ syndrome, which is caused by an extra chromosome 21.
Aneuploidy can result in conditions like ______ syndrome, which is caused by an extra chromosome 21.
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Which of the following is NOT a structural chromosomal abnormality?
Which of the following is NOT a structural chromosomal abnormality?
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What is the primary cause of aneuploidy?
What is the primary cause of aneuploidy?
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Polyploidy is a common condition in humans.
Polyploidy is a common condition in humans.
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Name one specific manifestation of chromosomal abnormalities.
Name one specific manifestation of chromosomal abnormalities.
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The condition where a chromosome has more than two complete sets is called ______.
The condition where a chromosome has more than two complete sets is called ______.
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Match the chromosomal abnormality to its description.
Match the chromosomal abnormality to its description.
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Which of the following is an example of a numerical abnormality?
Which of the following is an example of a numerical abnormality?
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Fertilization errors can occur if an egg is fertilized by two sperm.
Fertilization errors can occur if an egg is fertilized by two sperm.
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What are ring chromosomes?
What are ring chromosomes?
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An example of a chromosomal disorder caused by a structural abnormality is ______.
An example of a chromosomal disorder caused by a structural abnormality is ______.
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Which chromosomal abnormality typically involves breaking and reattaching segments?
Which chromosomal abnormality typically involves breaking and reattaching segments?
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What is the outcome when homologous chromosomes fail to separate during meiosis I?
What is the outcome when homologous chromosomes fail to separate during meiosis I?
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Monosomy refers to the gain of an extra chromosome.
Monosomy refers to the gain of an extra chromosome.
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Name a common example of trisomy.
Name a common example of trisomy.
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The chromosome number in Turner syndrome is described as _____ (2n-1).
The chromosome number in Turner syndrome is described as _____ (2n-1).
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Which trisomy typically results in early death due to severe developmental issues?
Which trisomy typically results in early death due to severe developmental issues?
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Polyploidy is common in humans.
Polyploidy is common in humans.
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What leads to triploidy in humans?
What leads to triploidy in humans?
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In humans, tetraploidy results from the failure of the _____ division.
In humans, tetraploidy results from the failure of the _____ division.
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Match the following conditions with their descriptions:
Match the following conditions with their descriptions:
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What might be a clinical implication of autosomal aneuploidies?
What might be a clinical implication of autosomal aneuploidies?
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Study Notes
Chromosomes, Karyotyping, and Chromosomal Abnormalities
- Chromosomes are thread-like structures made of DNA and proteins.
- Humans have 23 pairs of chromosomes (46 total).
- Chromosome structure includes a centromere, telomeres, and arms (p and q arms).
- Chromosomes carry genetic information essential for inheritance.
- Cytogenetic analysis examines chromosomes fixed during mitosis.
- During metaphase, DNA replicates and chromatin condenses.
- Sister chromatids are held together at the centromere.
- The centromere is a primary constriction point, vital for chromosome movement during cell division.
Chromosome Morphology
- Chromosomes vary in size, shape, and banding patterns.
- Karyotypes arrange chromosomes in pairs by size and centromere position (metacentric, submetacentric, acrocentric, telocentric).
- Metacentric chromosomes have the centromere in the middle.
- Submetacentric chromosomes have the centromere slightly off-center.
- Acrocentric chromosomes have the centromere close to one end.
- Telocentric chromosomes have the centromere at the very tip.
Karyotyping: Definition and Process
- Karyotyping is a genetic analysis technique to examine the chromosomal composition.
- It's critical for identifying and understanding chromosomal abnormalities.
- Chromosomes are stained (e.g., Giemsa stain), photographed, and arranged in pairs.
- Karyotyping identifies chromosomal abnormalities like aneuploidy and structural changes.
- FISH uses fluorescent probes for specific chromosomes to detect aneuploidies in specific cell populations.
- aCGH measures DNA quantities to detect unbalanced chromosomal abnormalities across the genome.
Advanced Karyotyping Techniques
- Karyotyping is a multi-step process involving cell preparation, chromosome staining, and analysis.
- Sample preparation involves culturing cells to stimulate division and arrest at metaphase for clearest visualization of chromosomes.
- Chromosome harvesting and staining involves treating cells with a hypotonic solution (to swell cells), fixing, and spreading chromosomes on slides.
- Chromosomes are stained to produce distinct banding patterns.
- Microscopic analysis and imaging involve examining chromosomes under a high-powered microscope to capture and arrange images based on size, banding patterns, and centromere position.
Approaches to Karyotyping – New and Old
- Classical Giemsa staining is a traditional approach for staining chromosomes.
- Fluorescence in situ hybridization (FISH) uses colored probes to highlight specific chromosomes, generating a spectral karyotype.
- Multiple probes target different parts of a chromosome to gain a better view of the chromosome structure, and identify any irregularities.
Numerical and Structural Chromosomal Abnormalities
-
Numerical Abnormalities
- Aneuploidy: An abnormal number of chromosomes (e.g., trisomy or monosomy).
- Trisomy: Presence of an extra chromosome (e.g., Down syndrome).
- Monosomy: Missing a chromosome (e.g., Turner syndrome).
- Polyploidy: More than two sets of chromosomes (rare in humans).
-
Structural Abnormalities
- Deletions: Loss of a chromosome segment.
- Duplications: Extra copies of a chromosome segment.
- Translocations: A segment of one chromosome moves to another.
- Inversions: A segment of a chromosome flips and reattaches in the reversed orientation.
- Ring chromosomes: Broken ends of a chromosome fuse into a ring.
Clinical Implications of Chromosomal Abnormalities
- Chromosomal abnormalities can lead to developmental delays, intellectual disability, increased risk of cancers, and other complications.
- Early diagnosis through karyotyping supports management and treatment.
- Karyotyping is used in prenatal screening, cancer diagnosis, and infertility evaluations.
- Abnormal karyotypes can guide treatment decisions, genetic counseling, and family planning.
- Diagnostic technologies include ultrasound, Karyotyping, FISH, and Quantitative Fluorescent PCR (QF-PCR).
Aneuploidy
- Aneuploidy is a chromosomal variation with an abnormal number of chromosomes (different from a complete set).
- Errors in chromosome segregation during meiosis or mitosis, typically during anaphase, lead to this.
- This results in gametes or cells with extra or missing chromosomes.
- The causes include non-disjunction—failure of sister chromatids or homologs to separate and anaphase lag—failure of a chromosome or chromatid to move to the spindle.
Polyploidy
- Polyploidy refers to cells or organisms with more than two paired sets of chromosomes.
- It's relatively common in plants but rare and often non-viable in humans.
- Causes include failed cytokinesis or fertilization errors.
- Polyploid fetuses often miscarry, or experience multiple congenital anomalies and organ system failures.
Detailed Examination of Chromosomal Abnormalities
- Chromosomal abnormalities are categorized into numerical and structural types.
- Aneuploidy: An individual has one extra or one less chromosome.
- Polyploidy: Condition where a cell has more than two complete sets of chromosomes.
- Structural abnormalities: Include translocations, deletions, duplications, inversions, and ring chromosomes.
Case Study Examples (Specific Syndromes)
- Trisomy 21 (Down Syndrome): extra chromosome 21, characterized by specific facial features, cognitive impairments, and increased risk of certain medical conditions.
- Monosomy X (Turner Syndrome): missing one X chromosome, characterized by short stature, lack of ovarian development, and characteristic physical features.
- Trisomy 18 (Edwards Syndrome) and Trisomy 13 (Patau Syndrome): severe developmental issues and often result in early death. The number of affected chromosome is different in each.
- Klinefelter Syndrome (47,XXY): extra X chromosome in males, characterized by tall stature, reduced fertility, and other unique features.
- Cri-du-chat Syndrome: partial chromosomal deletion on chromosome 5, characterized by a distinctive cry, feeding problems, and various physical and cognitive challenges.
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Description
Explore the fundamentals of chromosomes, karyotyping, and chromosomal abnormalities in this quiz. Understand the structure of chromosomes, the significance of their morphology, and the diagnostic techniques used in cytogenetics. Test your knowledge on these essential biological concepts related to genetic inheritance.
