Y Aa Number of alleles = 2XN
Ratio of A alleles in population (p) = = Or
Ratio of a alleles in population (r) = =
1st chemical mutagen = mustard gas (sulpher mustard)
HNO2 & alkylating agent like mustard gas are mutagens to both replicating & non replicas DNA
Mutagens only to replicating
(1) acridine dye – like proflavin bound to DNA
(2) Bass analogs – 5 – Bromouracil, 2- aminopurine
Genetic drift – in small population – Cause change in allele frequency when few Indi duals colonize a new habitat or when population greatly reduced due to a natural crash
Gene flow – transfer of alleles between the population
Cladogenesis (Divergent evolution) –
Convergent evolution – 2 different ancestors give rise to organism with similar physical & functional Character just as they are adapted to same environment
E.g., Euphorbia & cacti belong to difference families but adopted to same climate.
Coevolution – in nature species frequently interact so closely that evolutionary changes in one causes evolutionary adjustment in others – Flowering plant – insect pollinator predator – prey relation
Founder effect - species Type of genetic drift influencing genetic makeup of some population separating from the man population – fare less genetic variation & has a distinctive make up.
E.g., Dunbar’s of eastern - Pennsylvania migrated from Germany & U. S. in 1st century due to religious reasons they did not marry outside their caste/sect so the frequency of genes in 2 are different.
Bottleneck effect – due to drastic red in number of individuals in a population due to environmental factor e.g. population of cheetah of S & E. Africa reduced, now if provide protection only a part of the original gene pool will be recovered
Industrial melanism – directional selection on active – changing environment will lead to change in genotype/phenotype of population