State and explain any three factors affecting allele frequency in populations.
Factors affecting allele frequency in populations are as described below
(i) Mutations These are sudden heritable changes which are supposed to be the primary source of genetic variation. They are of following two types
(a) Chromosomal Mutations They arise due to changes in chromosome number and changes in structure.
(b) Gene Mutations These are changes in gene structure and expression due to addition, deletion, substitution or inversion of nucleotides.
(ii) Non-random Mating Repeated mating between individuals of certain selected traits changes the gene frequency, e.g., selection of more brightly coloured male bird by a female bird may increase the gene frequency of bright colour in the next generation.
(iii) Gene Flow (Gene Migration) It is the movement of alleles into and out of a gene pool. Breeding of immigrants with the host population adds new alleles to the gene pool of the host population.
Gene flow occurs through generations. Gene flow can occur across language barriers in humans. If we have a technique of measuring specific allele frequencies in different population of the world, can we not predict human migratory patterns in pre-history and history? Do you agree or disagree? Provide explanation to your answer.
Yes, we agree. As the gene flow occurs through geographical barriers over generations, by studying specific allelic frequencies in various populations of the world, we can predict the human migratory patterns in pre-historic and historic era.
There have been projects undertaken such as human genographics project. Which uses data from studies on specific genes/chromosomes/mitochondrial DNA to trace the evolutionary history and migratory patterns of humans.
How do you express the meaning of worlds like race, breed, cultivars or variety?
The meaning of the given words are as given below
Race It is a classification system used to categorise humans into large and distinct populations or groups by anatomical, cultural, linguistic, geographical, historical and for relegious relationship.
Breed It is a specific group of domestic animals or plants having homogenous appearance, homogenous behaviour and other characteristics that distinguish it from other animals or plants of the same species and that were arrived at through selective breeding.
Cultivar It is a plant or grouping of plants selected for desirable characteristics that can be maintained by propogation. 'Cultivar' stands for 'cultivated variety'.
Variety A variety arises naturally in the plant kingdom and plant grown from its seeds will typically come out true to type.
When we say 'survival of the fittest', does it mean that
(a) those which are fit only survive
(b) those that survive are called fit? Comment.
In the struggle for existence, the individuals which have more favourable variations will enjoy a competitive advantage over others which have less favourable or unfavourable variations.
They are considered fit and thus, will survive and reproduce. Such individuals produce more progeny (with more fit individuals) than others who are less adapted in that environment.
Enumerate three most characteristic criteria for designating a Mendelian population.
Characteristic criteria for designating a Mendelian population are
(i) Population must be sufficiently large.
(ii) Population must have potentialities for free flow of genetic material among individuals, through sexual reproduction.
(iii) Migration should either be nil or negligible.