Algae, Tree, Herbs, Bush, Shrub, Grasses, Vines, Fern, Moss, Spermatophyta, Bryophyta, Fern Ally, Flower, Photosynthesis, Eukaryote, Prokaryote, carbohydrate, vitamins, amino acids, botany, lipids, proteins, cell, cell wall, biotechnology, metabolities, enzymes, agriculture, horticulture, agronomy, bryology, plaleobotany, phytochemistry, enthnobotany, anatomy, ecology, plant breeding, ecology, genetics, chlorophyll, chloroplast, gymnosperms, sporophytes, spores, seed, pollination, pollen, agriculture, horticulture, taxanomy, fungi, molecular biology, biochemistry, bioinfomatics, microbiology, fertilizers, insecticides, pesticides, herbicides, plant growth regulators, medicinal plants, herbal medicines, chemistry, cytogenetics, bryology, ethnobotany, plant pathology, methodolgy, research institutes, scientific journals, companies, farmer, scientists, plant nutrition
Select Language:
 
   
 
 
Can't find? Try Deep Search with ePlantScience.com  
 
Share |
 
   
Main Menu
If navigation gets difficult, please click the main subject or sitemap to get the list of sub-categories
 
 
 
 
 
Related websites
 
 
 
 
 
 
 
 
Section: Genetics » Population Genetics : Gene Frequencies in Populations
 
 
If you like this page, please click:  
 
 
  Gene pool and gene frequencies
 
     
 
Content
⇒ Population Genetics : Gene Frequencies in Populations
⇒ Gene pool and gene frequencies
⇒ Equilibrium of gene frequencies and Hardy-Weinberg 
⇒ Frequencies of two alleles at a single locus
⇒ Frequencies of more than two alleles at a single locus
⇒ Frequencies of alleles at two or more loci
⇒ Changes in gene frequencies 
⇒ Mutations
⇒ Selection
⇒ Balance between mutation and selection
⇒ Migration
⇒ Random drift
Gene Pool and Gene Frequencies
Gene pool and gene frequencies are considered to be two important attributes of a population. A gene pool is the sum total of genes in reproductive gametes of a population. The gene pool is transferred from one generation to the other through the sample drawn from a gametic pool. This sample of gametes will form zygotes of next generation so that the gene pool of next generation will depend upon the kind of random samples drawn to form zygotes. Gene pool of a population will consist of a large number of genes which will vary in their frequencies. Gene frequencies are defined as proportions of different alleles of a gene in a population, and in a particular generation these frequencies will depend upon their frequencies in preceding generation. These frequencies also depend on proportion of various genotypes in total population. For instance, in human MN blood groups (Multiple Alleles (Based on Classical Concept of Allelomorphism)), if we sample a population of 100 individuals with 50MM, 20MN and 30NN, frequencies of 'M' and 'N' can be calculated.

Since each individual will have two homologous chromosomes each carrying a particular allele, the frequency of 'M' can be calculated by doubling the number of homozygous 'M' blood group type and adding to it the frequency of heterozygous 'MN' blood group type (because the heterozygote will have 'M' allele only on one of the two homologous chromosomes). In this manner the frequency of 'M' will be (50 x 2) + 20 = 120. In a similar manner the frequency of W will be (30 x 2) + 20 = 80. The relative frequencies of 'M' allele can be worked as
M
M + N
and that of 'N' can be worked out as
N
M + N
This will give us frequency of 'M' to be equal to
120
= 0.6
200
and that of N to be equal to
80
= 0.4
200
The frequencies of genes can also be worked out with the help of the following formula :
Frequency of gene = frequency of homozygote for that gene + ½ frequency of heterozygotes.

Using the above formula,
frequency of M = 0.5MM + ½ (0.2MN) = 0.6 and
frequency of N = 0.3NN + ½ (0.2MA0 = 0.4

 
     






     
     
 
 
     
 
Copyrights 2009 © ePlantScience.com