20 public questions tagged with this topic.
Alleles no blending recovered F2 law of segregation Mendel's second law.
Ref: NCERT Biology Class XII — Principles of Inheritance and Variation
Each individual inherits only two alleles for a gene, even if multiple alleles exist in the population. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.
Ref: NCERT Biology Textbook - Latest Edition for Academic Session 2026-27 (Botany section, Rationalized Textbook for Class XI and XII), Chapter: Biology - Botany portion (Latest NCERT Textbooks for Academic Session 2026-27 -
Some genes have more than two alleles, as seen in the ABO blood group system. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.
Hybridization entails controlled sexual crossing between individuals differing genotypically, from intraspecific crosses within same species to interspecific and intergeneric wide crosses. Procedure starts with selection of parents complementary for yield QTL, resistance R genes and quality alleles, followed by emasculation to prevent selfing, collection of viable pollen with intact exine and pollination at stigma receptive stage when peroxidase activity high. Fertilization leads to zygote formation and segregation in F2 generation through crossing over during pachytene and independent assortm
Ref: Allard Principles Plant Breeding Hybridization; Singh BD Methods hybridization; NCBI Bookshelf Plant Breeding chapter.
Mutations are random changes in the genetic material that lead to the formation of new alleles in a population.
Ref: NCERT Class 12 Biology Chapter 6: Evolution Mechanism of Evolution - Hardy-Weinberg and Natural Selection
An individual with two different alleles for a gene (e.g., Tt) is called heterozygous.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Polygenic Inheritance Pleiotropy and Quantitative Inheritance
In multiple allelism, a gene has more than two possible alleles in a population, but each individual inherits only two.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Monohybrid Dihybrid and Test Cross
A homozygous organism has two identical alleles for a trait.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Mendel's Laws - Dominance Segregation Independent Assortment
The Law of Independent Assortment states that different gene pairs assort independently during gamete formation.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Mendel's Laws - Dominance Segregation Independent Assortment
Law of segregation maintains that during gametogenesis alleles at any locus separate so each haploid gamete carries single representative. In heterozygous diploid, homologous chromosomes bearing alternative alleles disjoin, yielding equal proportions of allele-bearing gametes. Random fertilisation reconstitutes diploid genotype distribution. Phenomena like blending inheritance where alleles permanently mix, alleles remaining together in gametes, or obligate linkage contradict this law. Cytological demonstration via bivalent disjunction at anaphase I confirms physical basis and predicts recurre
Ref: NCBI Bookshelf, Genetics, Chapter: Mendel's First Law Segregation
Dihybrid cross analyses two independent characters simultaneously, such as seed shape and seed colour, each controlled by separate locus. Parental true-breeding lines differ in both traits, F1 diheterozygotes generate four gamete classes via independent assortment or recombination. Selfing produces sixteen combinations, collapsing to phenotypic ratio 9:3:3:1 under dominance and independence. Concept tests second law, differentiates linkage from unlinked behaviour and reveals epistatic interactions. One character or one gene defines monohybrid, two alleles only insufficient descriptor for two-l
Ref: Hartl & Ruvolo, Genetics, 9th ed., Chapter 2: Dihybrid Cross Analysis
Monohybrid cross involves analysis of single character differing between parents, for instance tall versus dwarf stem length governed by one gene with two alleles. Crossing pure-breeding lines TT by tt yields heterozygous F1, selfing exposes segregation. Focus remains phenotypic character though underlying gene counts one. Two genes or two characters would constitute dihybrid analysis requiring consideration of independent assortment and larger 16-combination Punnett. Monohybrid design clarifies dominance relationship, segregation ratio and gamete purity principle central to introductory genet
Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 2: Monohybrid Cross
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