1. Principle of paired factors.
2. Law of dominance. In a heterozygous individual only one allele is able to express its effect called dominant while the other remains hidden and is termed recessive.
3. Principle of purity of gametes. A gamete receives only one of the two
4. Principle of segregation. The two factors of a character keep their identity in an individual and do not blend. They segregate (separate) during gamete formation and are passed on to the offspring randomly after fertilization.
The Chromosomal theory of inheritance states that
1. Chromosomes as well as genes occur in pairs.
2. Two alleles of a gene pair are located on the homologous sites of homologous chromosome
3. The chromosome segregate and assort independently just like the genes during meiosis.
4. They recombine at the time of fertilisation in the zygote to re establish the parental chromosome number.
(b) The expected ratio will be 1 : 2 : 1. i.e. 1 black, 2 steel-blue and 1 white.
â–² Fig. 1.5
Both IA and IB are dominant and express themselves over IO or i. IA and IB show co-dominance and produce different forms of sugar wheras IO or i does not produce any sugar. The Thus the phenotypes produced are -:
IAIA and IAIO Produces the phenotype of A blood group.
IBIB and IBIO produces blood group B.
IAIB produces Blood group AB .
IOIO produces Blood group O.
1.Chromosomes and genes are found in pairs in diploid cells.
2. Both chromosomes and genes segregate in meiosis I.
3. Each gamete receives only one chromosome and one allele of the gene pair.
4. Paired condition of both is restored during fertilization.
5. Both chromosomes and genes retain their individuality throughout life cycle.
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