NCERT Solutions for Class 12 Biology Chapter 5 Principle of Inheritance and Variation to Study Online or Free download in PDF form. NCERT Books based on latest CBSE Syllabus is given to download for all the subjects.
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Solutions for 12 Biology Chapter 5
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Important Terms on Chapter 5
- Phenotype: The observable or external characteristics of an organism.
- Genotype: The genetic constitution of an organism.
- Aneuploidy: The phenomenon of gain or loss of one or more chromosome(s), that results due to failure of separation of homologous pair of chromosomes during meiosis.
- Trisomy: The condition in which a particular chromosome is present in three copies in a diploid cell/nucleus.
- Male heterogamety: When male produces two different types of gametes/sperms e.g., In human beings X and Y.
- Female Heterogamety: When female produces two different types of gametes/ova, e.g., female bird produces Z and W gametes.
Law of Dominance
When two individuals of a species differing in a pair of contrasting characters/traits are crossed, the trait that appears in the F1 generation is dominant and the alternate from that remain hidden, is called recessive.
Law of Segregation (law of purity of gametes): The members of allelic pair that remained together in the parent, segregate/separate during gamete formation and only one of the factors enters a gamete.
Law of Independent Assortment
In the inheritance of two pairs of contrasting characters (dihybrid cross) the factors of each pair of characters segregate independently of the factors of the other pair of characters.
Chromosomal Theory of Inheritance: Proposed by Sutton and Boveri. The pairing and separation of a pair of chromosomes would lead to the segregation of a pair of factors they carried. They united the knowledge of segregation with Mendelian principles.
The ability of a gene to have multiple phenotypic effects because it influences a number of characters simultaneously is known as pleiotropy. The gene having a multiple phenotypic effect because of its ability to control expression of a number of characters is called pleiotropic gene. E.g. in Garden Pea, the gene which controls the flower colour also controls the colour of seed-coat and presence of red spot in the leaf axis.