- A group of plants or animals comprising a species is characterized by a set of chromosomes, have certain constant features.
- These features include chromosome number, size and shape of individual chromosomes and other attributes listed above.
- The term karyotype is given to the group of characteristics that identifies a particular chromosome set and is usually represented by a diagram called ideogram where chromosomes of haploid set of an organism are ordered in a series of decreasing size.
- The karyotypes of different groups are sometimes compared and similarities in karyotype are presumed to represent evolutionary relationships.
- Karyotype also suggest primitive or advanced feature of an organism.
This is Two type
(A) Symmetrical karyotype
- In this karyotyping all chromosome contain median and sub median centromere and the difference in size of chromosome is not very distinct.
- Plant having this type of karyotyping regarded as primitive
(B) Asymmetrical karyotyping –
- In this type of karyotyping the chromosome possesses subterminal centromere.
- These chromosomes depict a great variety in size i.e. from small to long chromosome are present in this asymmetrical karyotype.
- Plant having this karyotyping are regarded as advanced hence it can be concluded that karyotype of an individual or species is also a means for understanding the evolutionary process
- A symmetric and an asymmetric karyotype are shown in figure
- In 1931 G. A. Levitzky, a Russian scientist suggested that in flowering plants there is a predominant trend towards karyotype asymmetry.
- This trend has been carefully studied in the genus Crepis of the family compositae.
- In several cases it was shown that increased karyotype asymmetry was associated with specialized zygomorphic flowers.
The karyotype of the human female contains 23 pairs of homologous chromosomes:
- 22 pairs of autosomes
- 1 pair of X chromosomes
The karyotype of the human male contains:
- the same 22 pairs of autosomes
- one X chromosome
- one Y chromosome
Process of Karyotyping
- A karyotype is a technique that allows geneticists to visualize chromosomes under a microscope.
- The chromosomes can be seen using proper extraction and staining techniques when the chromosomes are in the metaphase portion of the cell cycle.
- Detecting abnormalities is important for prenatal diagnosis, detection of carrier status for certain genetic diseases or traits, and for general diagnostic purposes.
Sterilization–
- It is an important step.
- All instruments and equipment’s should be properly sterilized.
Sampling and Culture–
- Karyotype analysis can be performed on virtually any population of rapidly dividing cells either grown in tissue culture or extracted from tumors.
- Chromosomes derived from peripheral blood lymphocytes are ideal because they can be analyzed three days after they are cultured.
- Lymphocytes can be induced to proliferate using a mitogen (a drug that induces mitosis) like phytohemagglutinin.
- Skin fibroblasts, bone marrow cells, chorionic villus cells,tumorcells, or amniocytes also can be used but require up to two weeks to obtain a sufficient amount of cells for analysis.
Cell Synchronization-
- The cultured cells are treated with colcemid, a drug that disrupts the mitotic spindle apparatus to prevent the completion of mitosis and arrests the cells in metaphase.
Harvesting and Slide preparation–
- The harvested cells are treated briefly with a hypotonic solution.
- This causes the nuclei to swell making it easier for technicians to identify each chromosome.
- The cells are fixed, dropped on a microscope slide, dried, and stained.
Observation in microscope –
- The most common stain used is the Giemsa stain.
- Other dyes, such as fluorescent dyes, can also be used to produce banding patterns.
Photography-
- Chromosome spreads can be photographed.
- Enlargement of photo and rearrangement to form Karyotype-
- The photographs are enlarged, cut out, and assigned into the appropriate chromosome number or they can be digitally imaged using a computer.
- In case of Human karyotype, there are seven groups (A-G) that autosomal chromosomes are divided into based on size and position of the centromere.
- The standard nomenclature for describing a karyotype is based on the International System.
Karyotype Evolution
- Two aspects of the process of speciation are of interest in the context of cytogenetics.
- The first of these is changes in ploidy i.e. changes in the number of the chromosomes, which themselves remain unaltered.
- Changes in ploidy can have both genetic and phenotypic effects, such as fertility changes, and can be used to great effecting plant breeding to produce new cultivars.
- Additional sets of chromosomes can be from the individual (autopolyploid) or from an organism of genetically distinct origin (allopolyploids).In the case of humans, changes in ploidy can have very severe consequences, as can the second process of interest: changes in karyotype.
- Karyotype changes can be thought of as being due to changes in either DNA content or chromosome structure as well as changes in chromosome numbers.
- In this context it is possible to see speciation and karyotype changes that are linked, as in the marsupials, or not linked, as in the hominids.
- Evolution and speciation are closely related to observable changes in an organism’s chromosomes.
- It should, however, be clearly borne in mind that karyotype changes are rarely enough for speciation to occur on their own. It is, after all, the phenotype expression of the genome which determines the position of the fine line, sometimes indefinable, between variation and speciation
🔹 1. The karyotype is usually represented by: (NEET 2021)
A. Genome map
B. Pedigree chart
C. Ideogram ✅
D. Kinetochore diagram
🔹 2. A symmetrical karyotype is a feature of: (CUET 2023)
A. Advanced species
B. Primitive species ✅
C. Polyploids
D. Mutants
🔹 3. A karyotype is best observed at which stage? (NEET 2020)
A. Interphase
B. Anaphase
C. Metaphase ✅
D. Telophase
🔹 4. The chromosomes used for human karyotyping are isolated from: (AIIMS PYQ)
A. RBCs
B. WBCs
C. Lymphocytes ✅
D. Platelets
🔹 5. Chromosomes are arrested in metaphase using: (CUET 2022)
A. Giemsa
B. Colchicine/Colcemid ✅
C. Trypsin
D. Acetocarmine
🔹 6. Which scientist proposed the concept of karyotype asymmetry in 1931? (UPSC Biotech PYQ)
A. Levitzky ✅
B. Sutton
C. Watson
D. Crick
🔹 7. Karyotype of human males includes: (NEET 2023)
A. 22 pairs + XX
B. 22 pairs + XY ✅
C. 23 pairs + X
D. 23 pairs + Y
🔹 8. A plant with subterminal centromeres and large size variation in chromosomes has: (CUET 2023)
A. Symmetrical karyotype
B. Asymmetrical karyotype ✅
C. Polyploid genome
D. Aneuploid karyotype
🔹 9. Which technique helps visualize chromosomes for karyotyping? (NEET 2022)
A. Spectrophotometry
B. Light microscopy
C. Staining during metaphase ✅
D. Flow cytometry
🔹 10. Phytohemagglutinin is used to: (AIIMS 2019)
A. Arrest mitosis
B. Stimulate mitosis ✅
C. Kill cells
D. Induce mutations
🔹 11. In humans, autosomes are grouped into how many groups in a karyotype? (NEET 2021)
A. 4
B. 5
C. 6
D. 7 ✅
🔹 12. Increased karyotype asymmetry in Crepis is correlated with: (UPSC PYQ)
A. Seed shape
B. Flower symmetry ✅
C. Leaf arrangement
D. Fruit type
🔹 13. Banding pattern for karyotype analysis is observed using: (CUET 2022)
A. Giemsa staining ✅
B. Gram staining
C. Acid-fast staining
D. Sudan III
🔹 14. Karyotyping is important for detection of: (NEET 2020)
A. Mutations in proteins
B. DNA methylation
C. Chromosomal abnormalities ✅
D. Bacterial infections
🔹 15. Chromosome size in ideogram is arranged in: (CUET 2021)
A. Random order
B. Ascending order
C. Descending order ✅
D. Alphabetic order
🔹 16. Cells are treated with hypotonic solution in karyotyping to: (NEET 2019)
A. Fix DNA
B. Shrink nuclei
C. Swell nuclei ✅
D. Break membranes
🔹 17. Colcemid arrests cells by disrupting: (CUET 2023)
A. DNA
B. RNA
C. Mitotic spindle ✅
D. Cell membrane
🔹 18. Ploidy changes without chromosome structure alteration lead to: (NEET 2018)
A. Aneuploidy
B. Polyploidy ✅
C. Chromosomal mutation
D. Inversion
🔹 19. In humans, sex chromosomes are represented in males as: (NEET 2022)
A. XX
B. XY ✅
C. YY
D. XO
🔹 20. Submedian centromeres are a feature of: (UPSC Biotech PYQ)
A. Symmetrical karyotype ✅
B. Asymmetrical karyotype
C. Acrocentric karyotype
D. Telocentric chromosomes
🔹 21. Which step is crucial to swell nuclei for better chromosomal spread in karyotyping? (NEET 2018)
A. Fixation
B. Colchicine treatment
C. Hypotonic treatment ✅
D. Mitogen induction
🔹 22. Autosomal chromosomes in human karyotype are grouped based on: (CUET 2023)
A. Gene location
B. Base composition
C. Size and centromere position ✅
D. Telomeric sequence
🔹 23. Amniocytes for karyotyping are obtained from: (NEET 2021)
A. Placenta
B. Amniotic fluid ✅
C. Umbilical cord
D. Ovary
🔹 24. A plant species with uniform chromosome sizes and median centromeres is: (CUET Mock PYQ)
A. Evolutionarily advanced
B. Symmetric karyotype ✅
C. Polyploid
D. Aneuploid
🔹 25. Digital karyotyping allows: (UPSC Biotech PYQ)
A. Chromosome elimination
B. Visual mutation
C. Gene editing
D. Computer-based chromosome arrangement ✅
🔹 26. Which of the following is a polyploidy-induced speciation event? (NEET 2020)
A. Fusion of gametes
B. Hybridization with chromosome doubling ✅
C. Point mutation
D. Gene silencing
🔹 27. Karyotyping is typically performed on cells arrested in: (NEET 2019)
A. Interphase
B. Metaphase ✅
C. Anaphase
D. Telophase
🔹 28. Colchicine/colcemid works by interfering with: (CUET 2023)
A. DNA unwinding
B. Actin filaments
C. Mitotic spindle fiber formation ✅
D. Cytokinesis
🔹 29. Which of the following is not a source of cells for karyotyping? (CUET 2021)
A. Bone marrow
B. Tumor cells
C. Mature RBCs ✅
D. Chorionic villus
🔹 30. The visual representation of a karyotype is termed as: (NEET 2022)
A. Cytogram
B. Ideogram ✅
C. Genotype chart
D. Genome map
🔹 31. In which group of organisms is karyotype asymmetry associated with specialized flowers? (UPSC 2018)
A. Lamiaceae
B. Compositae (Asteraceae) ✅
C. Poaceae
D. Solanaceae
🔹 32. The mitogen used to stimulate human lymphocytes for karyotyping is: (NEET 2021)
A. Giemsa
B. Ethidium bromide
C. Phytohemagglutinin ✅
D. Acetocarmine
🔹 33. The term ‘autopolyploid’ refers to: (CUET 2022)
A. Fusion of gametes from different species
B. Duplication of same genome within species ✅
C. Loss of chromosomes
D. Mutation in mitochondria
🔹 34. Which structure is NOT used in the grouping of human autosomes? (CUET PYQ)
A. Chromosome length
B. Position of centromere
C. Number of bands
D. Telomere structure ✅
🔹 35. Increased asymmetry in karyotype indicates: (NEET 2023)
A. Primitive traits
B. Advanced evolution ✅
C. Chromosomal aberration
D. Reduced fertility
🔹 36. Why is metaphase preferred for chromosome observation? (AIIMS 2018)
A. Easy to stain
B. Chromosomes are condensed and visible ✅
C. No mitotic activity
D. DNA replication is complete
🔹 37. A normal human male karyotype contains: (NEET 2021)
A. 44 autosomes + XX
B. 44 autosomes + XY ✅
C. 46 autosomes
D. 23 autosomes + X
🔹 38. What is the full set of chromosomes in a species called? (CUET 2022)
A. Genotype
B. Karyotype ✅
C. Genome
D. Idiotype
🔹 39. Which of the following is not required in karyotyping protocol? (CUET mock)
A. Mitogen
B. Hypotonic solution
C. Staining
D. Restriction enzyme ✅
🔹 40. What makes lymphocytes suitable for karyotyping? (NEET PYQ)
A. Easily available in blood and can be stimulated to divide ✅
B. Long chromosomes
C. Only haploid cells
D. Naturally divide rapidly
🔹 41. A karyotype showing chromosomes of different lengths and centromere positions is: (CUET 2023)
A. Homologous
B. Symmetrical
C. Asymmetrical ✅
D. Isokaryotype
🔹 42. Which human karyotype indicates Turner’s syndrome? (NEET 2020)
A. 45, XO ✅
B. 46, XXY
C. 47, XYY
D. 46, XX
🔹 43. Ploidy change without structural chromosome change is seen in: (UPSC 2019)
A. Inversion
B. Polyploidy ✅
C. Translocation
D. Robertsonian fusion
🔹 44. Which feature is most commonly used in arranging chromosomes in an ideogram? (CUET 2022)
A. GC content
B. Banding sequence
C. Size and centromere position ✅
D. Gene density
🔹 45. How many total chromosomes are found in a normal female karyotype? (NEET 2019)
A. 44
B. 46 ✅
C. 48
D. 42
🔹 46. What is the significance of banding pattern in karyotype? (CUET 2022)
A. Replication
B. Homologous recombination
C. Chromosome identification ✅
D. Cell growth
🔹 47. Subterminal centromere is typically seen in: (UPSC PYQ)
A. Symmetrical karyotype
B. Asymmetrical karyotype ✅
C. Telocentric chromosomes
D. Dicentric chromosomes
🔹 48. Karyotype analysis helps in identifying: (NEET 2020)
A. Genetic code
B. Chromosomal syndromes ✅
C. Codon frequency
D. Gene mutations
🔹 49. What is the importance of karyotype in evolution? (UPSC 2021)
A. Speciation evidence ✅
B. DNA replication
C. Gene expression
D. Genetic drift
🔹 50. Which of the following is NOT a direct result of karyotyping? (CUET 2023)
A. Identification of trisomy
B. Study of chromosomal morphology
C. Estimating protein sequence ✅
D. Detection of chromosomal deletions