Chromosome Isolation

10 Questions

What is the diploid chromosome number in humans?

Which cells are diploid in humans?

Skin cells

What do homologous chromosomes carry?

Different allels of the same genes

Which tissues are commonly used for chromosome analyses?

Amnion fluid

Which banding technique involves the use of a proteolytic enzyme, Trypsin, and Giemsa stain?

G banding

What is the purpose of adding colcemid in chromosome harvesting?

To prevent mitotic spindle formation

In karyotyping, how are chromosomes arranged?

Based on shape and size

Which technique is used for in situ detection of specific DNA sequences on metaphase chromosomes?

Fluorescence in situ hybridization (FISH)

What is the main purpose of adding Phytohemaglutinin (PHA) to culture medium?

To stimulate T lymphocytes to divide

Which type of individuals or tissue have two or more cell lines with different genetic constitution?

Mosaic individuals or tissue

Study Notes

Chromosome isolation can be achieved using the direct method, which involves obtaining chromosomes from spontaneously dividing cells, such as bone marrow cytotrophoblastic cells.
Culture techniques include short term (peripheral blood, bone marrow) and long term (amniotic cells, skin, solid tumor) methods.
Preparing culture medium involves adding fetal calf serum, certain amino acids, and antibiotics.
Heparinized blood is added to culture medium and Phytohemaglutinin (PHA) is used to stimulate T lymphocytes to divide.
Incubation is carried out at 37°C for 3 days, and medium changing is only required for long term cultures.
Chromosomes are harvested by adding colcemid to prevent mitotic spindle formation, followed by hypotonic shock and fixation.
Slides are prepared through chromosome spreading and staining using different banding techniques, such as G banding, Q banding, and R banding.
Under the microscope, good quality metaphases are scanned at 10x magnification, and metaphase analysis is carried out at 100x magnification to count chromosomes and examine for structural abnormalities.
Chromosomes are arranged in a karyogram, with the different groups based on shape and size of the chromosomes.
There are two types of banding techniques: differential banding techniques, which generate dark and light bands along the length of all chromosomes, and selective staining techniques, which stain distinct chromosomal regions.
G banding is the most common technique and involves the use of a proteolytic enzyme, Trypsin, and Giemsa stain.
Chromosomes can be examined in detail using high resolution banding (HRB), which identifies distinct chromosomal regions.
Mosaic individuals or tissue have two or more cell lines with different genetic constitution.
A karyotype designation includes the total chromosome number and sex chromosomes, with abnormalities presented in a specific order using abbreviations.
Techniques such as C banding, NOR banding, and fluorescence in situ hybridization (FISH) are used to detect specific chromosomal features.
C banding, NOR banding, and fluorescence in situ hybridization (FISH) are used to detect specific chromosomal features.
FISH uses DNA probes labeled with fluorescing dyes to bind complementary DNA sequences on metaphase chromosomes.
C banding stains centromeres and heterochromatic regions, NOR banding identifies Nucleolus Organizing Regions, and FISH is used for in situ detection of specific DNA sequences.