Columns X and Y of the following table list some treatment methods, reagents, and events that are related to human lymphocyte culture, and banding/ karyotyping of human chromosomes. Column X Column Y A. 5% barium hydroxide treatment at 50°C I. R-banding B. Trypsin treatment II. C-banding C. Phytohaemagglutinin III. Mitotic stimulation D. Phosphate buffer treatment at 80°C IV. Nucleolar Organizer Regions (NOR) E. Silver Staining v. G-banding Which one of the following options represents all correct matches between Column X and Column Y?
A - ii; B - v; C - iii; D - i; E - iv
Chromosome Banding & Karyotyping Techniques
Understanding the techniques used in human chromosome analysis, such as banding and karyotyping, requires knowledge of specific treatments and their outcomes. This question asks us to match various treatments, reagents, and events involved in human lymphocyte culture and chromosome analysis with their corresponding outcomes or uses.
Let's examine each pairing based on common cytogenetic protocols:
Treatments and Banding Methods
- A. 5% barium hydroxide treatment at 50°C: This specific treatment is a crucial step in the C-banding technique. C-banding is used to stain constitutive heterochromatin, which is typically located around the centromeres of chromosomes and on the distal part of the long arm of the Y chromosome. Therefore, A matches with II. C-banding.
- B. Trypsin treatment: Trypsin is an enzyme used in G-banding. Before staining with Giemsa, chromosomes are often treated with trypsin. This partial digestion of chromosomal proteins leads to the differential staining pattern observed as G-bands, which are rich in A-T base pairs and repetitive DNA. Thus, B matches with V. G-banding.
- C. Phytohaemagglutinin: Phytohaemagglutinin (PHA) is a lectin derived from plants. It is widely used as a mitogen in lymphocyte cultures to stimulate T lymphocytes to divide. Obtaining chromosomes at the metaphase stage, when they are most condensed and visible, requires stimulating cell division. Therefore, C matches with III. Mitotic stimulation.
- D. Phosphate buffer treatment at 80°C: Treatment with hot phosphate buffer is a technique used to denature DNA differently along the chromosome, allowing for R-banding (Reverse banding). R-bands are the reverse of G-bands; they are AT-poor and GC-rich regions and stain darkly with Giemsa after this treatment. This technique is useful for analyzing terminal deletions or specific chromosome regions. Thus, D matches with I. R-banding.
- E. Silver Staining: Silver staining is a technique specifically used to stain the Nucleolar Organizer Regions (NORs). NORs are loops of ribosomal DNA found on the short arms of human acrocentric chromosomes (chromosomes 13, 14, 15, 21, and 22). The silver stain highlights proteins associated with active rRNA genes in these regions. Therefore, E matches with IV. Nucleolar Organizer Regions (NOR).
Based on this analysis, the correct matches are: A - ii, B - v, C - iii, D - i, E - iv.
Let's summarize these matches in a table:
| Column X (Treatment/Reagent/Event) | Column Y (Banding/Event) | Match |
|---|---|---|
| A. 5% barium hydroxide treatment at 50°C | II. C-banding | A - ii |
| B. Trypsin treatment | V. G-banding | B - v |
| C. Phytohaemagglutinin | III. Mitotic stimulation | C - iii |
| D. Phosphate buffer treatment at 80°C | I. R-banding | D - i |
| E. Silver Staining | IV. Nucleolar Organizer Regions (NOR) | E - iv |
Comparing these matches with the given options, the option that correctly represents all these pairings is A - ii; B - v; C - iii; D - i; E - iv.
Important Questions from Human genetics
Mendel selected which of the following traits for his studies?
Two strains of mice which are genetically identical except for a single genetic locus or region are said to be:
Interacting genes which are involved in producing continuous variation in phenotypes in a population are known as/constitute
Sampling of 200 persons for their ABO blood group was done from an urban area. The types of blood group observed in the given population are as follows:
A = 60, B = 32, AB = 10 and O = 98
Which of the following gives the correct frequency of blood group determining alleles IA , IB and IO in the given population?
The table given below shows the Lod score values of three different pairs of genes studied for assessing if they are linked pairs:
Gene Pair '1' Gene Pair '2' Gene Pair '3' Lod Score 1 2 3 The following conclusions were made from the data given above:
A. For gene pair 1 the probability of the genes being linked is 10 times more likely than them assorting independently.
B. For gene pair 2, the Lod score 2 indicates that the probability of the genes being linked is twice more likely than assorting independently.
C. The genes of pair 1 and 2, can both be considered as linked, while the genes of pair 3 exhibits independent assortment.
D. The genes of pair 3 can be considered as linked.
Which one of the following options represents statement(s) that is/are correct?
