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Chapter List
Cell Cycle Chromosome – I: Architecture and Special Types of ChromosomesChromosome – II: Karyotyping, Banding and Chromosome Painting
Chromosome – III: Structural and Numerical Variations
Chromosome – IV: Chromosome Number and Aneuploidy
Chromosome – V: Variation in Chromosome Behaviour
Chromosome – VI: Chromosomal Aberrations and Chromosome Complexes
Fertilization Barriers in Crop Plants
Polyploidy and Aneuploidy in Crop Breeding
Apomixis, Polyploid Genome Mapping and Interspecific Hybridization
Synthesis of New Crops and Wide Hybridization
Gene Transfer and Chromosome Manipulation in Wide Hybridization
Haploids, Dihaploids and Doubled Haploids in Genetics and Breeding
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Syllabus
Content: Cell cycle and architecture of chromosome in prokaryotes and eukaryotes; Chromonemata, chromosome matrix, chromomeres, centromere, secondary constriction and telomere; artificial chromosome construction and its uses; Special types of chromosomes.Variation in chromosome structure: Evolutionary significance; Introduction to techniques for karyotyping; Chromosome banding and painting –In situ hybridization and various applications. Structural and numerical variations of chromosomes and their implications; Symbols and terminologies for chromosome numbers, euploidy, haploids, diploids and polyploids; Utilization of aneuploids in gene location; Variation in chromosome behaviour, somatic segregation and chimeras, endomitosis and somatic reduction; Evolutionary significance of chromosomal aberrations, balanced lethal and chromosome complexes; Inter-varietal chromosome substitutions. Fertilization barriers in crop plants at pre-and postfertilization levels; In-vitro techniques to overcome the fertilization barriers in crops; Polyploidy. Genetic consequences of polyploidization and role of polyploids in crop breeding; Evolutionary advantages of autopolyploid vs allopolyploids; Role of aneuploids in basic and applied aspects of crop breeding, their maintenance and utilization in gene mapping and gene blocks transfer; Alien addition and substitution lines, creation and utilization; Apomixis, evolutionary and genetic problems in crops with apomixes. Reversion of autopolyploid to diploids; Genome mapping in polyploids; Interspecific hybridization and allopolyploids; Synthesis of new crops (wheat, Triticale, Brassica, and cotton); Hybrids between species with same chromosome number, alien translocations; Hybrids between species with different chromosome number; Gene transfer using amphidiploids, bridge species. Chromosome manipulations in wide hybridization; case studies; Production and use of haploids, dihaploids and doubled haploids in genetics and breeding. Practical: Learning the cytogenetical laboratory techniques, various chemicals to be used for fixation, dehydration, embedding, staining, cleaning, etc.; Microscopy: various types of microscopes; Preparing specimen for observation; Fixative preparation and fixing specimen for light microscopy studies in cereals; Studies on mitosis and meiosis in crop plants; Using micrometres and studying the pollen grain size in various crops. Pollen germination in vivo and in-vitro; Demonstration of polyploidy.
Frequently Asked Questions (FAQs) – Cytogenetics
1. What is cytogenetics?
Cytogenetics is the branch of genetics that deals with the study of chromosomes, their structure, number, behaviour, variation and role in heredity, evolution and plant breeding.
2. What are the main stages of the cell cycle?
The cell cycle consists mainly of interphase and the division phase. Interphase includes G1, S and G2 phases, while the division phase includes mitosis or meiosis. DNA replication occurs during the S phase.
3. What is a centromere?
A centromere is a specialized region of a chromosome where sister chromatids remain associated and spindle fibres attach through the kinetochore during cell division. It plays an important role in accurate chromosome segregation.
4. What are telomeres and what is their function?
Telomeres are specialized DNA-protein structures present at the ends of linear chromosomes. They protect chromosome ends from degradation, fusion and abnormal recognition as damaged DNA.
5. What is karyotyping?
Karyotyping is the systematic arrangement and examination of chromosomes according to their number, size, shape, centromere position and other structural features. It is useful for identifying chromosomal abnormalities and studying genetic relationships.
6. What is chromosome banding?
Chromosome banding is a technique used to produce characteristic light and dark patterns on chromosomes. Common methods include G-banding, C-banding, Q-banding and NOR-banding. These patterns help in chromosome identification and comparison.
7. What are chromosomal aberrations?
Chromosomal aberrations are structural or numerical changes in chromosomes. Structural aberrations include deletion, duplication, inversion and translocation, whereas numerical changes include aneuploidy and polyploidy.
8. What is aneuploidy?
Aneuploidy is a condition in which the chromosome number differs from the normal chromosome complement by the addition or loss of one or more individual chromosomes. Examples include monosomics (2n−1) and trisomics (2n+1).
9. What is polyploidy?
Polyploidy is the condition in which an organism possesses more than two complete sets of chromosomes. Polyploids may be autopolyploids, formed from chromosome sets of the same species, or allopolyploids, containing chromosome sets derived from different species.
10. What is the difference between autopolyploidy and allopolyploidy?
Autopolyploidy involves multiplication of chromosome sets from the same species, while allopolyploidy results from combining chromosome sets from different species, usually following interspecific hybridization and chromosome doubling.
11. What is apomixis?
Apomixis is a form of asexual reproduction through seeds in which a normal sexual process is bypassed and embryos develop without the usual fertilization process. It can help maintain desirable genetic combinations in crop plants.
12. What are fertilization barriers in crop plants?
Fertilization barriers are factors that prevent successful fertilization between particular plants. They may occur before fertilization, such as pollen-stigma incompatibility and pollen tube failure, or after fertilization, such as embryo abortion, endosperm failure and hybrid sterility.
13. How can fertilization barriers be overcome?
Fertilization barriers can be overcome using techniques such as bud pollination, mentor pollen, cut-style pollination, in-vitro pollination, embryo rescue, ovule culture, ovary culture and, in some cases, somatic hybridization.
14. What is wide hybridization?
Wide hybridization refers to crossing genetically distant plants, particularly different species or genera. It is used to introduce useful genes for disease resistance, pest resistance, abiotic stress tolerance, quality and other desirable traits into crop plants.
15. What is an alien addition line?
An alien addition line is a plant in which one or more chromosomes from another species are added to the normal chromosome complement of the crop. Such lines are useful for locating genes and transferring useful traits from wild or related species.
16. What is an alien substitution line?
An alien substitution line is a cytogenetic stock in which a chromosome of the crop is replaced by a corresponding chromosome from another species. These lines are useful in chromosome identification, gene localization and the transfer of desirable genetic variation.
17. What is an alien translocation?
An alien translocation occurs when a chromosome segment from another species becomes attached to a chromosome of the crop plant. It is an important method for transferring useful genes while attempting to reduce the amount of undesirable linked alien genetic material.
18. What is chromosome manipulation in wide hybridization?
Chromosome manipulation involves techniques used to alter chromosome number, pairing or composition to facilitate gene transfer between distantly related plants. Chromosome doubling, chromosome substitution, alien addition and translocation are important examples.
19. What are haploids, dihaploids and doubled haploids?
A haploid plant contains a single basic chromosome set. A dihaploid is a haploid-derived plant with the diploid chromosome number, commonly produced from a doubled haploid process in a diploid species. Doubled haploids are produced by chromosome doubling of haploid cells or plants and are completely homozygous, making them valuable in plant breeding.
20. What is the importance of cytogenetics in plant breeding?
Cytogenetics provides essential information about chromosome number, structure, pairing and behaviour. It supports chromosome identification, gene mapping, polyploid breeding, wide hybridization, alien gene transfer, development of addition and substitution lines, production of doubled haploids and the synthesis of new crops.
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Last Updated: August 2026
