Population Genetics,Mendelian Genetics,Gene pool & Deme Notes

Population Genetics

Structure of Populations

The branch of genetics which 

deals with hereditary mechanism

in groups of individuals or

 population that changes from 

generation to generation is termed as 
population genetics.
When hereditary phenomenon of any character is studied at 
population level,the study then becomes population genetics.

Genes in Population:

In contrast to genetic studies with 

plants and animals,the study of human genetics cannot make use of experimental 

crosses between organisms of given types. Matings that occur spontaneously can,however be observed and their progeny be recorded.

MENDELIAN POPULATION

Mendelian population is defined 

as unit of measurement of population and 

evolution. A group of marriages within 

which marriages are assortative or contracted is called as Mendelian population.

This branch also deals with the concept 

of gene pool and the transmission of genes in population.

Difference between Population Genetics 

and Evolutionary genetics:

Population genetics deals with the 

population of a given species of

an organism while Evolutionary genetics

deals with hereditary mechanism in any 

population whether of same or 

different species.

The objective of population genetics is to

study the genetic composition of populations. The basic unit of study in

population genetics is gene rather than 

genotype of an individual as population 

consists of individuals of different genotypes. Each gene can maintain its 

identity for all generations.

Whereas a genotype does not 

necessarily reproduce its own identity. Hence, a population is characterized by a set of gene frequencies, which are the  essential requirements for studying the genetics of any population.
Knowledge of population genetics is essential for understanding the mechanism
of evolution, since evolution is a process of cumulative change of genetic composition
of populations.

As mentioned earlier the Mendelian population deals with the concept of gene pool.

What is Gene Pool?

Answer: Gene pool is the
aggregate(collection)of genotypes of all individuals in a given population, For diploid organisms (2n), the gene pool with 'N' individuals consists of 2N haploid genomes.
Each genome consists of all the information
received from one parent.
Thus, in a gene pool of a given population of 'N' individuals, there are 2N genes for each gene locus and 'N' pairs of homologous chromosomes.

Deme:

Deme is referred to a local population

and is applied to individuals of the 

same species, whether they reproduce sexually or not. Local populations

of a sexually reproducing organism may be

with ill defined population boundaries.

Consider an oat population, Avena sativa, which exists along the foot hills of the Coast Ranges of California. This is now considered as a local population of wild slender oat, which exists as cluster of individuals.