Principles of Inheritance And Variation – Notes
First and Second Laws of Inheritance
Gregor Johann Mendel carried out several hybridization experiments with true-breeding pea lines which had sharply contrasting characters.
A monohybrid cross is the study of inheritance of one pair of contrasting characters.
The Law of Dominance states that in a monohybrid, pure line cross between parents with contrasting traits, the dominant from appears in the F1 generation and both forms appear in a ratio of 3:1 in the F2 generation.
The Law of Segregation states that alleles do not show any blending but segregate from each other during gamete formation into different gametes.
Punnett Square is a graphical representation that helps calculate the probability of all possible genotypes of the progeny in a genetic cross.
A test cross is a cross between individuals if the F1 generation and a homozygous recessive parent to determine the genotype of an individual.
Chromosomal disorders are caused due to changes in chromosomal number or chromosomal structure.Changes in chromosomal number occur due to non-disjunction of chromosomes or failure of chromatids to disjoin during cell-division.