29 Questions
What is the main target of T-Banding staining technique?
Telomeres
Which staining technique selectively stains the constitutive heterochromatin around the centromeres?
Q-Banding
Which staining method focuses on the terminal ends or telomeres of chromosomes?
R-Banding
Where are the nucleolar organizer regions (NORs) located?
On acrocentric chromosomes' satellite stalks
Which technique allows the visualization of individual chromosomes in metaphase or interphase cells?
Chromosome Painting
What is the purpose of Chromosome Painting?
Identification of structural chromosomal aberrations
What staining method is most widely used for routine chromosome banding?
Giemsa Banding
What specific regions of the chromosomes do the dark bands represent in G-Banding?
A-T-rich, late replicating, heterochromatic regions
What is the main purpose of collecting fetal blood for karyotyping?
To obtain a rapid karyotype
What must be done to the prepared slides before staining them with Giemsa in G-Banding?
Treat with trypsin
What provides information about the number and type of sex chromosomes in karyotype analysis?
Metaphase chromosomes
What is the purpose of studying constitutive heterochromatin regions in chromosome banding studies?
To identify specific chromosome abnormalities
What type of specimen is most preferred for karyotyping?
Heparinized peripheral blood
Which specimen is useful for studying hematologic disorders?
Bone marrow aspirates
What do chorionic villus samples offer as an advantage over amniotic fluid for prenatal analysis?
Karyotypes are available within a day or two
What type of sample contains amniotic cells and is obtained through insertion into the amniotic sac?
Amniotic fluid
Which specimen is considered an excellent source if obtained soon after death during autopsy or fetal loss?
Tissues
For prenatal analysis, which specimen can be obtained earlier in the pregnancy than amniotic fluid?
Chorionic villus sample
What is the main focus of karyotyping?
Examining the structure of chromosomes
When is the best phase to study for karyotyping?
Metaphase
What does karyology refer to?
Study of whole sets of chromosomes
What is the purpose of identifying families with chromosomal aberrations?
To understand health impacts
What does a karyogram or ideogram depict?
The chromosomes in a standard format
What is the significance of karyotyping in population studies?
Revealing environmental toxin effects
Which banding method developed for human chromosomes uses a fluorescent technique?
Q-Banding
What bases are primarily found in the DNA of quinacrine-bright bands?
Adenine (A) and Thymine (T)
What regions of chromosomes stain darkly or fluoresce brightly in R-Banding?
C-G rich, euchromatic regions
Which banding technique selectively depurinates and denatures DNA using barium hydroxide?
C-Banding
Which banding method is useful for evaluating euchromatic terminal ends that are hard to visualize with G-banding?
R-Banding
Study Notes
Karyotyping
- Karyotyping is a cytogenetics test that examines the structure and behavior of chromosomes at the cellular level.
- A karyotype is the number and appearance of chromosomes in the nucleus of a eukaryotic cell.
Chromosome Preparation
- Metaphase chromosomes are used for karyotyping, as they have aligned centromeres and have not yet divided.
- Chromosome preparation involves staining and dyeing to produce patterns of bands specific to each chromosome.
Banding Techniques
- G-Banding (Giemsa Banding): most widely used routine banding method, produces dark bands (A-T rich, late replicating, heterochromatic regions) and light bands (C-G rich, early replicating, euchromatic regions).
- Q-Banding (Quinacrine Banding): fluorescent technique, produces distinct banding pattern of bright and dull fluorescence, with quinacrine-bright bands rich in A-T and quinacrine-dull bands rich in G-C.
- R-Banding (Reverse Banding): opposite of G-Banding pattern, with C-G rich regions staining darkly or fluorescing brightly, and A-T rich regions staining lightly or fluorescing dully.
- C-Banding (Constitutive Heterochromatin Banding): useful for determining dicentric chromosomes and polymorphic variants, and for studying evolutionary relationships.
- T-Banding (Telomere Banding): a harsh treatment that diminishes staining except at the heat-resistant telomeres.
- NOR Staining (Silver Staining for Nucleolar Organizer Regions): stains nucleolar organizer regions on acrocentric chromosomes.
- Chromosome Painting (CP): uses fluorescent dyes to generate unique patterns for each chromosome, allowing visualization of individual chromosomes in metaphase or interphase cells.
Specimen Types
- Heparinized peripheral blood: most preferred, easy, and relatively painless.
- Bone marrow aspirates: for studying hematologic disorders, sample is the origin of disease.
- Skin biopsies: fibroblast cultures.
- Tissues: kidney, liver, muscle, lung, excellent source if obtained soon after death during autopsy or fetal loss.
- Amniotic fluid: obtained through amniocentesis, contains amniotic cells.
- Chorionic villus sample: useful for prenatal analysis, advantages over amniocentesis include earlier performance and faster karyotype availability.
Karyotyping Objectives and Applications
- Objectives: to understand the structure of chromosomes, to understand various banding techniques and their applications, and to identify the sex of individuals via amniocentesis.
- Applications: confirms clinical prognosis, identifies families and relatives with chromosomal aberrations, and is used in population studies to reveal the effects of environmental toxins.
Test your knowledge on Karyotyping, a specialized laboratory discipline that examines the structure and behavior of chromosomes in cellular level. Learn about the number and appearance of chromosomes in Eukaryotic cells, the complete set of chromosomes in a species, and the best phase to study - metaphase.
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