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: General Cell & Molecular Biology » Molecular Evolution
 
 
If you like this page, please click:  
 
 
  Phylogenetic Analysis
 
     
 
Content
⇒ Molecular Evolution
     ⇒ Early Beginnings
     ⇒ The RNA World
     ⇒ The DNA World
     ⇒ Phylogenetic Analysis
     ⇒ The Evolution of Eukaryotic Cells


Proteins evolve at different rates because of intrinsic factors (repair mechanisms) and extrinsic factors (environmental mutagens). Highly conserved proteins apparently have only been able to tolerate a few minor changes, whereas some other proteins have been able to absorb many mutations without loss of function. Mutations that occur outside a region involved with normal function of the molecule may be tolerated as a selectively neutral mutation. Over geological time, these neutral mutations tend to accumulate within a geneological lineage. If it is assumed that such neutral mutations accumulate at a fairly constant rate for a highly conserved protein, it is possible to establish the branching pattern of a phylogenetic tree (also called a cladogram or an evolutionary tree).




The principle of parsimony is commonly used to determine the minimum number of genetic changes required to account for the amino or nucleotide sequence differences between organisms sharing a common ancestor. The evolutionary distances separating organisms in a phylogenetic tree are usually expressed in units of nucleotide mutations or amino acid substitutions along each arm of the tree between branch points (see Figure 12-1).



Notes
Some evolution rates (point mutations per 100 million years):
Triose phosphate isomerase = 3
Hemoglobin = 21
Nonfunctional pseudogenes = 400
 
     





     
     
 
 
     
 
Copyrights 2009 © ePlantScience.com