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17 Cards in this Set
- Front
- Back
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Define karyotype.
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Karyotype - description of the normal/abnormal and constitutional/acquired chromosomal complement of an person, tissue, or cell line.
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What types morbidities/mortalities do chromosome study elucidate? or why get the karyogram for somebody?
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1. unrecognized early embryonic death
2. recognized embryonic and fetal death 3. females with pubertal anomalies 4. sex reversal/ambiguous genitalia 5. congenital heart defects 6. birth defects 7. infant and childhood deaths 8. multiple miscarriage in couples |
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From what cells can chromosomes be obtained?
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Chromosomes must be gathered from LIVING tissue in which SOMATIC cells are actively dividing (MITOSIS).
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What are the six tissues suitable for chromosome studies?
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1. Peripheral blood lymphocytes
2. Bone marrow 3. Chorionic villus biopsy 4. Amniotic fluid cells 5. Fetal blood cells via percutaneous umbilical blood sampling 6. Skin or organ biopsy |
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What are the short hand notations for the long and short arm for an individual chromosome and the genetic short hand for normal males and females.
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-short arm [p]
-long arm [q] -female: 46,XX -male: 46,XY |
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Define the following chromosome descriptive terms:
1. Metacentric 2. Submetacentric 3. Acrocentric |
1. Metacentric - centromere in the middle. eg. 3
2. Submetacentric - centromere displaced from the center (most common). eg. 17, 18 3. Acrocentric - centromere near the end. eg. 21, 22 |
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How many bands are distinguishable on a:
1. High Resolution - Prophase 2. Middle - Mid Metaphase 3. Low - Metaphase |
1. Prophase - 850 (targeted searches)
2. Mid-Metaphase - 550 (most common) 3. Metaphase - 300-400 |
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Diagnostic Testing: G-banding
1. What is the pre-treatment step? 2. What stains are used? 3. What nomenclature is used? |
1. Pre-treatment is done by trypsin or heat (protease)
2. Most common DNA stain is Giemsa (good for human DNA) 3. GTG-banding or GTW-banding i.e. Generalized appearance-Trypsin-Giesma |
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Describe the FISH test - Fluorescence in situ hybridization.
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A process by which the chromosomal location of a specific piece(s) of DNA is identified.
It's like finding the one car in the parking lot. You use a labeled probe that is specific for the chromosome DNA segment. |
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What is SKY - spectral karyotyping?
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Allows cytogeneticist to observe ALL 24 chromosomes simultaneously. A computer will analyze the color concentration. Utilizes painting probes.
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Compare AneuVysion vs. Karyotyping
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AneuVysion - prenatal screen taken immediately (interphase). Good to provide quick information
Standard testing - cells need to be raised in culture (7-10 days). |
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What are the three types of probes used in FISH testing?
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1. Locus specific probes - one per homolog, detects microdeletions
2. Satellite DNA enumeration probe - generates bigger signals, good if you want to know how many chromosomes there are (extra or minus). 3. Painting probes highlight the entire length. Good for metaphase analysis. Structural rearrangements |
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What are CGH arrays? (Comparative genomic hybridization aka array testing)
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Array CGH provides a bridge between high resolution of FISH and the low resolution but broad view of karyotype analysis. The array approach is equivalent to performing thousands of FISH experiments at one time.
Strength - ID small imbalances (high resolution) Weakness - doesn't allow for balance rearrangements or ploidy changes |
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What are the basics of array technology, using and reading the results?
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Arrays allow hybridization between patient DNA and control DNA. Greater binding occurs when patient DNA contains an extra chromosome and this is shown via color intensity.
Often times you use an opposite gender control to confirm the assay is working correctly. |
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Compare Chorionic and Amniocentesis in Prenatal diagnosing.
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Amniocentesis (14-16 weeks) - use with ultrasound, get cells, grow cells, get karyotype. risk=1 in 100-200
CVS (10 weeks) - use ultrasound and get chorionic villi, raise it, and get karyotype |
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Compare the prenatal test, Percutaneous umbilical blood sampling, with the pregnancy failure
Stillbirths test. |
1. High risk procedure, get blood from umbilical cord. Can be resolved quickly.
2. Perform chromosome testing for the mental comfort of the parents. |
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Why would you do postnatal chromosome testing?
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1. Newborns with congenital malformations
2. Adolescents with delayed growth and/or sexual development 3. Adults with a history of infertility 4. Families with a history of mental retardation. 5. Neoplasms or pre-malignant lesions (skin cancer for when you are much older) |
