Emergence of different varieties or species The phenomenon of genetic diversity describes naturally occurring genetic differences among individuals of the same species.

"Variation" is the term used in genetics, and refers to the emergence of different varieties, or species. This genetic phenomenon causes individuals or groups within a given species to possess different features from others. For example, all human beings on Earth possess essentially the same genetic information. But thanks to the genetic variation potential permitted by that genetic information, some people have blue eyes, or wavy hair, or long nose, beautiful skin, or short and stocky in stature.

Genetic variation occurs mainly through sexual reproduction (recombination/crossing over), independent assortment (random pattern of inheritance), Gene Flow (movement of genes from one population to another) and the very important DNA mutations. Due to the fact that environments are unstable, populations that are genetically variable will be able to adapt to changing situations better than those that do not contain genetic variation.

Genetic variation permits flexibility and survival of a population in the face of changing environmental circumstances. It also describes naturally occurring genetic differences among individuals of the same species. Optimistically, genetic variation is often considered as an advantage, as it is a form of preparation for the unexpected.

Changes in DNA is the ultimate source of genetic variations Whether you’re looking at people, birds, or maple trees, diversity within population begins with DNA.

Every bird in a flock or every fish in a pond may look the same to us, but just as no two people are exactly alike, individuals within all species vary. Every day we see people who vary in ways that are easy to see, like our shapes and sizes. We also vary in ways that are less obvious, like personality, susceptibility to disease, and ability to tolerate certain types of food. Individuals in other species differ from each other too, often even more so than humans. And whether you're looking at people, birds, or maple trees, diversity within population begins with DNA.

Genetic variation can occur on several different levels, including changes to a specific gene, modifications of gene expression, and alterations in proteins. Genetic variations can range in size from macroscopic to sub-microscopic. They can take the form of gross structural changes in chromosomes, missing or extra genetic information, or minute errors in the spelling of the genetic code. Each type of genetic change requires a different technology for detection. Let's start finding out the reasons behind the genetic diversity.

Meiosis helps to generate improved variety Meiosis is important because it ensures genetic diversity in cells during reproduction.

During fertilization, one "gamete" from each parent combines to form a "zygote". Because of recombination and independent assortment (one of the Mendel's laws) in meiosis, each gamete contains a different set of DNA. This produces a unique combination of genes in the resulting zygote.

Meiosis also produces genetic variation by way of the process of recombination. Later, this variation is increased even further when two gametes unite during fertilization, thereby creating offspring with unique combinations of DNA. This constant mixing of parental DNA in sexual reproduction helps fuel the incredible diversity of life on Earth.

Recombination and independent assortment allow for a greater diversity of genotypes in the population. Each of the homologous pairs of chromosomes may orient with either its maternal or paternal homologue closer to a given pole. Thus, there is a 50% chance that a particular daughter cell of meiosis it will get the maternal chromosome of a certain homologous pair and a 50% chance that it will receive the paternal chromosome.

This reshuffling of genes into unique combinations increases the genetic variation in a population and explains the variation we see between siblings with the same parents.Thus, meiosis helps to generate improved variety, and results incredible diversity of life on Earth.

Individuals with Sickle Cell Anemia are immune to malaria. Sickle cell anemia is a genetic disease that causes red blood cells to be shaped like sickles while normal red blood cells are shaped more like a cylinder. Malaria works by going into the red blood cells until they burst. Because of the strange shape of the red blood cells in people who have sickle cell anemia, malaria can't enter in the cells that have the sickle trait, but it can enter in the others. This way, people with sickle cell wouldn't be as adversely effected then those without it.

A positive effect of DNA mutations - Apolipoprotein AI-MilanoA small community in Italy is known to have a mutant version of this protein, named Apolipoprotein AI-Milano which removes cholesterol most effectively from the blood stream.

Most random genetic changes are neutral, and some are harmful, but a few turn out to be positive improvements. These beneficial mutations are the raw material that may, in time, be taken up by natural selection and spread through the population. Let's  list some examples of beneficial mutations that are known to exist in human beings.

• Sickle cell anemia: An example of a somewhat positive genetic mutation is Sickle Cell Anemia.  Individuals with Sickle Cell Anemia are immune to malaria.  The genetic damage to the blood cells make them inhospitable to the malaria virus. Sickle cell anemia is a genetic disease that causes red blood cells to be shaped like sickles while normal red blood cells are shaped more like a cylinder. Malaria works by going into the red blood cells until they burst. Because of the strange shape of the red blood cells in people who have sickle cell anemia, malaria can't enter in the cells that have the sickle trait, but it can enter in the others. This way, people with sickle cell wouldn't be as adversely effected then those without it.
• Apolipoprotein AI–Milano: Heart disease is one of the scourges of industrialized countries. It's the legacy of an evolutionary past which programmed us to crave energy–dense fats, once a rare and valuable source of calories, now a source of clogged arteries. But there's evidence that evolution has the potential to deal with it. All humans have a gene for a protein called Apolipoprotein AI, which is part of the system that transports cholesterol through the bloodstream.

Apo–AI is one of the HDLs, already known to be beneficial because they remove cholesterol from artery walls. But a small community in Italy is known to have a mutant version of this protein, named Apolipoprotein AI-Milano, or Apo–AIM for short. Apo-AIM is even more effective than Apo–AI at removing cholesterol from cells and dissolving arterial plaques, and additionally functions as an antioxidant, preventing some of the damage from inflammation that normally occurs in arteriosclerosis.

People with the Apo–AIM gene have significantly lower levels of risk than the general population for heart attack and stroke, and pharmaceutical companies are looking into marketing an artificial version of the proteinas a cardioprotective drug. There are also drugs in the pipeline based on a different mutation, in a gene called PCSK9, which has a similar effect. People with this mutation have as much as an 88% lower risk of heart disease. [Source: Evolution Is Still Happening: Beneficial Mutations in Humans]

CCR5-delta 32 mutation – Bringing revolution in HIV treatment A genetic mutation found mostly in people of European descent delays the progression of AIDS and in some cases even brings about immunity.

A genetic mutation known as CCR5-delta 32 is responsible for the two types of HIV resistance that exist. CCR5-delta 32 hampers HIV's ability to infiltrate immune cells. The mutation causes the CCR5 co-receptor on the outside of cells to develop smaller than usual and no longer sit outside of the cell. CCR5 co-receptor is like door that allows HIV entrance into the cell. The CCR5-delta 32 mutation in a sense locks "the door" which prevents HIV from entering into the cell. 1% of people descended from Northern Europeans, particularly Swedes, are immune to HIV infection. These lucky people are homozygous carriers of the mutated gene - meaning that they inherited a copy from both of their parents. Another 10 -15% (the number has even suggested to be18%) of people with European heritage inherited one copy of the gene. Just one copy of the mutation does not prevent against infection. It does however reduce carrier's chances of infection and delays the progress of AIDS. Since the CCR5-delta 32 is tied primarily to the Eurasia region, the mutation has not been found in Africans, East Asians, or Amerindians.

Why does the CCR5-delta 32 mutation appear in people of European descent only? There is no solid answer to this question yet but many theories have been suggested. Along this line of reasoning scientists have suggested that past epidemics were the driving force behind the prevalence of the mutation in Europeans. CCR5-32 Delta is exciting. It presents possibilities for new ways to protect against HIV. Many wonder if genetic testing is available yet to see if one has the mutation.  Understanding how and why certain people are resistant to HIV/AIDS with the help of CCR5-32 Delta will hopefully lead to new and highly successful treatments in our lifetime. [Source: www.nature.com]