Course Content
Qualitative and quantitative characters (qualitative and quantitative characters in crops and their inheritance)
0/2
Biometrical techniques in plant breeding (assessment of variability, aids to selection, choice of parents, crossing techniques, genotype-by- environment interactions)
0/3
Selection in self-pollinated crops (progeny test, pureline theory, origin of variation, genetic advance, genetic gain)
0/5
Hybridization techniques and its consequences (objectives, types, program, procedures, consequences)
0/4
Genetic composition of cross-pollinated populations (Hardy-Weinberg law, equilibrium, mating systems)
0/4
Breeding methods in self-pollinated crops (Mass, Pure line, Pedigree, Bulk, Backcross, etc)
0/5
Learn Introductory Plant Breeding with Rahul

Example of Hardy-Weinberg law

  • Let us consider a single gene with two alleles, A and a, in a random mating population.
  • There would be three genotypes, AA, Aa and aa, for this gene in the population. Suppose the population has N individuals of which D individuals are AA, H individuals are Aa and R individuals are aa so that D +H + R = N.
  • The total number of alleles at this locus in the population would be 2N since each individual has two alleles at a single locus.
  • The total number of A alleles would be 2D+H because AA individuals have two A alleles each, while each Aa individual has only one A allele.
  • The ration (2D+H)/2N is, therefore, the frequency of A allele in the population, and is represented by p.
  • Similarly, the ratio (2R + H) / 2N is the frequency of allele a, and is written as q.

 

 

Therefore, p = (2D + H) / 2N or = (D + ½ H) / N and

q = (2R + H) / 2N or = (R + ½ H) / N

Therefore, p + q = 1

and p = 1 – q,

or q = 1 – p

 

  • The value of p and q are known as gene frequencies. Gene frequency is the proportion of an allele, A or a, in a random mating population.
  • The genotype frequency or zygotic frequency is the proportion of a genotype, AA, Aa or aa, in the population.
  • Random mating or random union of the two types of gametes would produce the following genotypes in a ratio proportionate to the frequencies of the gametes that united to produce them.
Scroll to Top