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An introduction

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STUDENT TASKS

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Video by Richard Thomas Lankes as a part of his "Genetic Mutations" Science Suitcase for STARS at UT Southwestern, Dallas. Narration by Brina Palencia. Funding by HHMI. Joel Goodman, STARS Director. See more info at utsouthwestern.edu/STARS. Part 2 at: http://vimeo.com/32422180 Check out our other videos on Evolution: vimeo.com/19796663, Photosynthesis: vimeo.com/18544535 and Cell Membranes: vimeo.com/31411881 !

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Mutation Generates New Alleles

The whole human family is one species with the same genes. Mutation creates slightly different versions of the same genes, called alleles. These small differences in DNA sequence make every individual unique. They account for the variation we see in human hair color, skin color, height, shape, behavior, and susceptibility to disease. Individuals in other species vary too, in both physical appearance and behavior.

Genetic variation is useful because it helps populations change over time. Variations that help an organism survive and reproduce are passed on to the next generation. Variations that hinder survival and reproduction are eliminated from the population. This process of natural selection can lead to significant changes in the appearance, behavior, or physiology of individuals in a population, in just a few generations.

Once new alleles arise, meiosis and sexual reproduction combine different alleles in new ways to increase genetic variation.

It's useful to think of mutation as a process that creates genetic variation. We often refer to a mutation as a thing-the genetic variation itself. This approach can be useful when it comes to a gene associated with a disease: the disease allele carries a mutation, a DNA change that compromises the protein's function. However, this approach gives mutation a bad name.

It's important to remember that losing the function of a gene doesn't always affect health. For example, most mammals have hundreds of genes that code for olfactory receptors, proteins that help us smell. Losing one of these genes probably doesn't make all that much difference.

In contrast to variations that cause disease, there are many more examples of variations that are neither good nor bad, but just different-like blood types and eye color. Just like with disease alleles, the process of mutation creates these more neutral variations. But with neutral variations, it can be impossible to tell which allele is the "normal" one that existed first and which is the "mutant"-and the distinction is often meaningless.

Mutation creates variations in protein-coding portions of genes that can affect the protein itself. But even more often, it creates variations in the "switches" that control when and where a protein is active and how much protein is made.

Lactase is an enzyme that helps infants break down lactose, a sugar in milk. Normally the gene that codes for lactase is active in babies and then turned off at about age four. When people who don't make lactase consume milk, they experience gas, nausea, and discomfort. But some people have a variation in a genetic switch that keeps the lactase gene active. This variation is called "lactase persistence," and people who have it can keep milk in their diets even as adults.

Other drivers of mutation: Environmental agents

Radiation, chemicals, byproducts of cellular metabolism, free radicals, ultraviolet rays from the sun-these agents damage thousands of nucleotides in each of our cells every day. They affect the nucleotides themselves: converting one base to another, knocking a base off its backbone, or even causing a break in the DNA strand.

Most of the time, mutation is reversed. DNA repair machines are constantly at work in our cells, fixing mismatched nucleotides and splicing broken DNA strands back together. Yet some DNA changes remain. If a cell accumulates too many changes-if its DNA is so damaged that repair machinery cannot fix it-it either stops dividing or it self-destructs. If any of these processes go wrong, the cell could become cancerous.

When we put on sun screen, we are protecting ourselves against mutation in somatic cells-the cells that make up the body and are not involved in reproduction.&ZeroWidthSpace; Only when DNA changes are carried in egg and sperm cells are they passed to the next generation. Believe it or not, a certain amount of sloppiness is built into the system. Without mutation there would be no variation, and without variation there would be no evolution.

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Mutation Generates New Alleles The whole human family is one species with the same genes. Mutation creates slightly different versions of the same genes, called alleles. These small differences in DNA sequence make every individual unique. They account for the variation we see in human hair color, skin color, height, shape, behavior, and susceptibility to disease.

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More than 99 percent of your genetic information is exactly the same as every other person on the planet. Your genes determine your skin colour, sex, and hair colour and whether or not you have certain genetic diseases.

But it's in that less than 1 percent that things get interesting. Specific genetic variations allow some of us to acquire certain - dare we say super - qualities. Here are the ways our genes can predispose us to have special abilities.
ACTN3 and the super-sprinter variant
We all have a gene called ACTN3, but certain variants of it help our bodies make a special protein called alpha-actinin-3. This protein controls fast-twitch muscle fibres, the cells responsible for the speedy tensing and flexing of the muscles involved in sprinting or weight-lifting.

This discovery, which happened around 2008 when geneticists studying elite sprinters and power athletes found that very few among them had two defective ACTN3 copies, is what led to the gene being dubbed the 'sports gene'.

Among the general population, however, some 18 percent of us are completely deficient in the speedy-muscle-contracting protein - we inherited two defective copies of ACTN3.
hDEC2 and the super-sleeper mutation
Imagine if you could feel totally energised on just 4 hours of sleep each night. Some people are naturally that way.

These people are called 'short-sleepers', and scientists are only recently uncovering what exactly predisposes them to be this way.

For the most part, researchers believe that the capabilities are connected to specific genetic mutations, and have publicly identified one on the hDEC2 gene.

That means that short-sleeping habits can run in the family, and scientists hope to one day learn how to harness this ability so it can be used to help people switch up their sleeping routines.
TAS2R38 and the supertaster variant
About a quarter of the population tastes food way more intensely than the rest of us.

These 'super tasters' are more likely to put milk and sugar in bitter coffee, or avoid fatty foods. The reason for their reaction, scientists think, is programmed into their genes, specifically one called TAS2R38, the bitter-taste receptor gene.

The variant responsible for super tasting is known as PAV, while the variant responsible for below-average tasting abilities is known as AVI.
LRP5 and the unbreakable mutation
Brittle bones pose a big problem. Researchers have identified a genetic mutation on the LRP5 gene that regulates bone-mineral density, which can cause brittle, weak bones.

So far, scientists have identified multiple mutations to the LRP5 gene that appear to be linked with bone conditions, including juvenile primary osteoporosis and osteoporosis-pseudoglioma syndrome.

But a different type of mutation on the same gene could also have the opposite effect, giving some people extremely dense bones that are practically unbreakable.
The malaria-protecting variant
People who are carriers for sickle-cell disease - meaning that they have one sickle gene and one normal haemoglobin gene - are more protected against malaria than those who are not.

Though blood disorders are not necessarily 'super', this information may influence more innovative malaria treatments down the road.
CETP and the low-cholesterol mutation
Although environment - including what we eat - can influence cholesterol levels, genetics play a big role, too.

Mutations in a gene responsible for producing a protein called cholesteryl ester transfer protein (CETP) result in a deficiency of that protein. CETP deficiency is linked with having higher levels of 'good' HDL cholesterol, which helps carry cholesterol to the liver so it can be removed from the body, resulting in lower cholesterol levels.

Studies have also found a lower prevalence of coronary heart disease in people with the deficiency-causing mutation.
BDNF and SLC6A4 and the super coffee-drinker variants
There are at least six genes associated with how your body processes caffeine.

Some variants, near the genes BDNF and SLC6A4, influence the rewarding effects of caffeine that make you want to drink more.

Others are linked to how the body metabolises caffeine - those who break caffeine down more quickly may be more likely to drink more of it because the effects wear off faster.

Others still help explain why some people are able to fall asleep at night after their daily morning coffee while others have to cut out the habit altogether to get a good night's sleep.
ALDH2*2: The super-flusher variant
Do your cheeks go rosy shortly after having a single glass of wine? A mutation on the ALDH2 gene may be the culprit.

One such mutation interferes with the ability of a liver enzyme called ALDH2 to convert the alcohol byproduct acetaldehyde into acetate.

When acetaldehyde builds up in the blood, it opens up the capillaries, causing what we see as a flush or glow.

But there's another dangerous component of acetaldehyde - it's a carcinogen in people, and research suggests that people who flush when they drink alcohol may have the mutation and may also be at a greater risk of esophageal cancer.
This article was originally published by Business Insider. More from Business Insider:

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8 Genetic Mutations That Can Give You 'Superpowers'

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More than 99 percent of your genetic information is exactly the same as every other person on the planet. Your genes determine your skin colour, gender, and hair colour and whether or not you have certain genetic diseases. But it's in that less

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Genetic Mutation | Learn Science at Scitable

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A single mutation can have a large effect, but in many cases, evolutionary change is based on the accumulation of many mutations with small effects. Mutational effects can be beneficial, harmful, or neutral, depending on their context or location. Most non-neutral mutations are deleterious.