Metaphase Chromosome Transfer (MCT)
Definition:
Metaphase Chromosome Transfer is a technique used to transfer individual chromosomes from a donor cell into a recipient cell. This allows the study of the genetic contribution of a single chromosome in isolation, analysis of gene function, mapping of genes, and creation of somatic cell hybrids.
It is a type of somatic cell genetics technique.
1. Principle
Chromosomes are isolated from donor cells arrested in metaphase (because metaphase chromosomes are condensed and visible).
The isolated chromosome is then introduced into a recipient cell, usually a rodent or human cell, which can be deficient in certain chromosomes.
The recipient cell can then express the genes present on the transferred chromosome, allowing functional analysis.
Key idea: Chromosomes, rather than whole cells, are transferred, enabling the study of individual chromosomes in a controlled environment.
2. Procedure / Steps
Cell Culture Preparation
Donor cells (human or other) are cultured.
Recipient cells (often rodent cells like mouse L-cells) are prepared. These usually lack the chromosome(s) of interest, so that any effect of transfer is detectable.
Metaphase Arrest
Donor cells are treated with colcemid or colchicine to halt them in metaphase.
Metaphase arrest ensures chromosomes are highly condensed and easy to isolate.
Chromosome Isolation
Cells are lysed gently to release chromosomes.
Chromosomes are separated individually under a microscope using micro-manipulation techniques.
Chromosome Transfer
A micropipette or micromanipulator is used to transfer the chromosome into a recipient cell.
Fusion may also be assisted chemically (e.g., using PEG – polyethylene glycol) or electrically (electrofusion).
Selection of Hybrid Cells
Recipient cells are grown under selective conditions that allow only those that have successfully received the chromosome to survive.
Example: If the transferred chromosome carries a drug-resistance gene, only cells expressing it survive in media containing that drug.
Verification
Successful transfer is confirmed by karyotyping or molecular markers specific to the donor chromosome.
3. Applications of MCT
Gene Mapping
Identifying which chromosome carries a particular gene.
Mapping genes associated with diseases (e.g., genetic disorders).
Functional Analysis
Study of gene function by expressing donor genes in recipient cells.
Production of Monosomic or Partial Hybrids
Creation of somatic cell hybrids with a single human chromosome in a rodent background.
Pharmacogenomics and Toxicology
Studying drug responses or toxic effects of specific genes.
Cancer Research
Introducing chromosomes to see which ones suppress tumorigenicity in cancer cell lines.
4. Advantages
Allows study of individual chromosomes rather than whole genomes.
Enables precise gene mapping.
Can generate stable somatic cell hybrids for research.
Useful in identifying chromosome-specific functions.
5. Limitations
Technically challenging and labor-intensive.
Requires specialized equipment like micromanipulators.
Not all chromosomes may be stably maintained in recipient cells.
Selection may be time-consuming.
50 MCQs on Metaphase Chromosome Transfer
Principle & Basics
MCT is used to transfer:
A) Whole cell nucleus
B) Individual chromosomes ✅
C) RNA
D) Mitochondria
The chromosomes for MCT are isolated at which stage?
A) Interphase
B) Anaphase
C) Metaphase ✅
D) Telophase
The donor chromosomes are highly condensed in:
A) Prophase
B) Metaphase ✅
C) Anaphase
D) Telophase
MCT is a type of:
A) Gamete transfer
B) Somatic cell genetics ✅
C) Viral transduction
D) Microinjection of mRNA
The recipient cell in MCT is usually:
A) Same species as donor
B) Chromosome-deficient rodent cell ✅
C) Bacterial cell
D) Yeast cell
Arresting Chromosomes
Which drug is commonly used to arrest cells in metaphase?
A) Penicillin
B) Colcemid/Colchicine ✅
C) Streptomycin
D) Doxorubicin
Colcemid works by:
A) Depolymerizing actin filaments
B) Disrupting microtubules ✅
C) Breaking DNA
D) Activating centrosomes
Arresting cells in metaphase is important because:
A) Chromosomes are decondensed
B) Chromosomes are condensed and visible ✅
C) Cells divide faster
D) RNA synthesis is active
Without metaphase arrest, chromosomes would be:
A) Easy to transfer
B) Highly visible
C) Diffused and difficult to isolate ✅
D) Drug-resistant
Colchicine is derived from:
A) Wheat
B) Autumn crocus ✅
C) E. coli
D) Yeast
Chromosome Isolation
Chromosomes are isolated using:
A) Centrifugation only
B) Micromanipulation ✅
C) PCR
D) ELISA
Micromanipulation uses:
A) Laser
B) Microscope and micropipette ✅
C) Electrophoresis
D) Flow cytometer
Isolated chromosomes are transferred into:
A) Donor cells
B) Recipient cells ✅
C) Bacteria
D) Viruses
Isolation of a single chromosome allows:
A) Whole-genome analysis
B) Study of individual gene function ✅
C) RNA synthesis
D) Protein degradation
Chromosome isolation must be:
A) Violent
B) Gentle ✅
C) Heat-assisted
D) Enzyme-digested
Transfer Techniques
Which is NOT a method for chromosome transfer?
A) Microinjection
B) Electrofusion
C) PEG fusion
D) PCR amplification ✅
PEG stands for:
A) Polyethylene glycol ✅
B) Protein energy gel
C) Phosphate ester glycol
D) Polyglucose enzyme
Electrofusion uses:
A) Heat
B) Electric pulse ✅
C) Centrifugation
D) Colchicine
Microinjection involves:
A) Viral vectors
B) Direct injection using micropipette ✅
C) Liposomes
D) Electrophoresis
Which step ensures that only cells with transferred chromosomes survive?
A) Chromosome isolation
B) Selection ✅
C) Metaphase arrest
D) Microinjection
Selection & Verification
Selective growth often uses:
A) Antibiotic or drug resistance markers ✅
B) DNA sequencing
C) PCR
D) Microscopy
Verification of transferred chromosome is done by:
A) Karyotyping ✅
B) ELISA
C) RNA-Seq
D) Western blot
Marker genes in MCT allow:
A) Chromosome condensation
B) Survival of only hybrid cells ✅
C) Faster cell division
D) DNA replication
Which method confirms donor chromosome presence at molecular level?
A) FISH (Fluorescence in situ hybridization) ✅
B) Gram staining
C) ELISA
D) Bradford assay
Chromosome transfer is stable when:
A) Chromosome is integrated into recipient genome ✅
B) Chromosome floats in cytoplasm
C) Cell dies
D) Chromosome is fragmented
Applications
MCT is used for:
A) Protein purification
B) Gene mapping ✅
C) RNA transcription
D) Bacterial culture
Useful in identifying genes responsible for:
A) Drug resistance ✅
B) Photosynthesis
C) Ribosome assembly
D) Glycolysis
MCT can produce:
A) Full genome hybrids
B) Monosomic or partial hybrids ✅
C) Viruses
D) mRNA clones
In cancer research, MCT helps identify:
A) Tumor-suppressor chromosomes ✅
B) Mitochondrial function
C) Membrane proteins
D) Ribosomal RNA
MCT is NOT used for:
A) Functional gene studies
B) Whole genome sequencing ✅
C) Somatic cell hybrid creation
D) Mapping human chromosomes
Advantages
Study of single chromosomes is possible because:
A) All genes are expressed
B) Only one chromosome is transferred ✅
C) RNA is removed
D) Proteins are degraded
MCT allows:
A) Analysis of all chromosomes simultaneously
B) Chromosome-specific function study ✅
C) Faster mitosis
D) Viral replication
Advantages of MCT include:
A) Precise gene mapping ✅
B) No need for recipient cells
C) Cheap and easy
D) Works in bacteria
Somatic cell hybrids from MCT are:
A) Stable for gene analysis ✅
B) Only temporary
C) Used in bacteria
D) Not selectable
MCT is preferred over whole-genome transfer because:
A) Easier to isolate
B) Focus on single chromosome ✅
C) Cheaper
D) Works without culture
Limitations
MCT is:
A) Technically easy
B) Technically challenging ✅
C) Cheap
D) Fully automated
Requires which specialized equipment?
A) Flow cytometer
B) Micromanipulator ✅
C) PCR machine
D) Spectrophotometer
Not all transferred chromosomes are:
A) Condensed
B) Stable ✅
C) Selectable
D) Drug-resistant
Limitation of MCT:
A) Can only transfer RNA
B) Labor-intensive ✅
C) Works in bacteria
D) Cannot arrest cells
Hybrid selection may take:
A) Minutes
B) Hours
C) Days to weeks ✅
D) Seconds
Technical Details
Donor chromosomes often come from:
A) Bacteria
B) Human or animal cells ✅
C) Yeast
D) Plant leaves
Recipient cells are usually:
A) Same species
B) Chromosome-deficient rodent cells ✅
C) Bacterial
D) Plant protoplasts
A drug-resistance gene is an example of:
A) Donor chromosome
B) Selectable marker ✅
C) Recipient chromosome
D) Metaphase arrest agent
PEG-mediated fusion combines:
A) RNA
B) Cell membranes ✅
C) DNA fragments
D) Protein complexes
Karyotyping identifies:
A) RNA
B) DNA sequence
C) Chromosome number and structure ✅
D) Protein content
Advanced & Conceptual
MCT contributed to mapping which human gene?
A) Beta-globin ✅
B) Actin
C) Collagen
D) Myosin
FISH is preferred because it:
A) Detects chromosomes visually ✅
B) Digests DNA
C) Inhibits growth
D) Only stains RNA
Somatic cell hybrid analysis helped in:
A) Identifying chromosome 21 involvement in Down syndrome ✅
B) Producing insulin
C) Photosynthesis
D) Ribosomal synthesis
MCT is a part of:
A) Classical genetics
B) Somatic cell genetics ✅
C) Microbiology
D) Immunology
The main goal of MCT is:
A) Transfer of mitochondria
B) Study of individual chromosome function ✅
C) RNA expression
D) Viral transformation
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