Humans actually use bile acids to absorb fat-soluble vitamins and not fat itself. However, once these vitamins are absorbed they are stored in adipose tissues (fat). When you need them, your body takes them out of storage to be used.
Whether you are eating a fatty diet or not, your body produces lipids (fats) through a metabolic system called Lipogenesis which converts carbohydrates into fat. As long as your diet is balanced and you are getting the correct amount of daily calories for your gender and height, you shouldn't need to increase your fat intake. However, you should note that it is actually more beneficial to you if you get your fat soluble vitamins from the ingestion of food rather than taking them as a supplement.
1. Can just one letter change in the DNA, in the right place, actually change behavior of the Gene in a significant and functional way?
It can change the function of the protein synthesized via the gene, but it depends on whether the mutation is a conservative change or a non conservative change.
As you may already know, DNA or more specifically the singular genes within DNA are the blue prints for making proteins. After DNA is transcribed into RNA, the RNA bases are read in triplicates which code for amino acids. 3 bases in a specific order = 1 amino acid.
Example: The triplicates CAC result in the amino acid Histidine. The triplicates AGC result in the amino acid Serine. The list goes on...
Each gene specifies how the amino acids will be sequenced. One full sequence of amino acids is called a polypeptide (AKA a single stranded protein). The sequence of amino acids specify how the single strand of protein will fold into it's final shape. The shape of the protein is extremely important because the shape determines it's function. The reason genetic diseases arise is because mutations cause the protein to fold incorrectly which renders it semi - completely dysfunctional.
There are 20 amino acids. Each have different molecular properties. For example: Practically everything in a living organism comes in contact with water. The amino acid Leucine is very hydrophobic, meaning it hates water and will do whatever it can to stay out of water. On the other hand, the amino acid Serine is very Hydrophilic, meaning it loves water so it will do what it can to be in the water. Lets assume that a normal (non mutated) protein strand has many hrdrophobic amino acids in one area of it's strand and many hydrophilic amino acids in another area of it's strand. The hydrophobic region will do whatever it can to be away from the water so it folds inwards. The hydrophilic area will want to be in the water so it folds outwards. So, depending on the amino acid and where they are located on the protein strand determines how the protein will fold. There are many other factors involved in protein folding but it would take an extreme amount of explaining. I just wanted to give you a quick example!
The reason single base mutations can be damaging is because they can turn one amino acid into another. For example: if the mutation turns a hydrophilic amino acid into a hydrophobic amino acid, that amino acid will no longer want to be in the water and will cause the protein to fold differently. This is called a non conservative mutation and they can greatly impact the function of a protein leading to disease.
On the other hand, a single base mutation can be conservative and will not impact the way a protein folds. For example: if the mutation turns a hydrophobic amino acid into another hydrophobic amino acids, the protein folding will be less impacted and it will retain it's function.
Another fact to consider is that amino acids can be coded by more than one triplicate sequence. There can be a single base mutation but it may still code for the same amino acid.
2. How do changes involving more than just one letter evolve?
I'm not quite sure what you're asking here. As you asking why multiple base mutations happen or how evolution works at the molecular level? If you can clarify, I will try my best to answer
It is very common for there to be several forms of the same virus. For example, the common cold is caused by several different viruses. Once you've had a cold, you generally build up immunity so you won't usually become ill from the same cold virus again. Therefore, when you experience another cold in the future it is usually caused by a different type of cold virus.
The herpes virus you are specifically referring to is called herpes simplex, which is an infection that affects the skin and nervous system, and produces small temporary blisters on the skin and mucous membranes. There are two types of herpes simplex: Type I and Type II.
Herpes infection occurs when herpes simplex virus enters the body through the nose, mouth, genitals, open sores etc. and travels into human nerve cells. The virus can be inactive for years and may never wake up. The virus can become active due to a decrease in the immune system. This can be brought on by other illnesses, stress, surgery, some medications etc.
Type I herpes (HSV-1) commonly causes the herpes blisters around the mouth. In some instances, type I herpes can cause blisters on genitals due to oral to genital contact. Type I is usually transmitted by kissing someone who has open herpes blisters, sharing a toothbrush, using the same lipstick etc. Type I can also cause Ocular Herpes in extreme cases.
Type II (HSV-2) cause genital herpes. You can get Type II during sexual contact with someone who has a genital HSV-2 infection. Some people may not be aware that they are infected thus easily spreading the virus to their partner if they are not using protection.
To wrap up your question:
A virus can come in different types which can lead to similar but slightly different infections. The area of outbreak depends on the type of herpes virus contracted, the origin of contraction (mouth, eyes, genitals etc.), and your immune system's ability to control the virus. The stronger your immune system, the less areas of breakout, whereas a weak immune system could result is large areas of your body being covered in blisters.
Hi Guys! I'm Chelsie. I'm an American biomedical scientist living Brisbane, Australia and finishing a masters in human physiology. My main areas of interest include human physio/anatomy, molecular genetics, molecular biology, human pathology, and medicine. In 2010 I'll be off to medical school but before I get too bogged down, I plan on enjoying this lovely forum!
I look forward to having some excellent discussions!
Here is a simplified run down on how gene therapy works:
We use gene therapy to correct/treat genetic mutations that can alter the way in which a gene is expressed. Genes are transcribed into RNA which encodes for proteins. Therefore the gene sequence is directly related to the function of the protein (protein shape dictates function). Some mutations, small or large, can alter the folding of polypeptides into an incorrect shape, which can render a protein semi dysfunctional or completely dysfunctional. This is how genetic diseases arise.
We can correct this by inserting a normal gene into the genome of a human cell to replace the dysfunctional gene that is causing the disease. There are several ways to accomplish this but the most common way is to use a vector. A vector is a molecule that carries and transfers genetic material into a cell. For example, viruses can be used as vectors and are one of the most common vectors we use in gene therapy.
As you can see from the image, the virus lands on a host cell and injects it's genetic material. The viral genetic material is then transcribed within in the cell to make more viruses. The host cell eventually bursts and the new viruses are released to repeat the process.
A viral vector uses the same process, however they do not carry viral genetic material and are genetically engineered to specifically carry and inject human genetic material into the human host cell. This means that the viral vector can carry the normal genetic material and inject it into a human cell with a mutated gene. The new and correct gene produces new and correct protein. With more newly functional protein being synthesized, the genetic disease will become less sever and can even be cured in some cases. The cells with the new and correct gene will then replicate, creating millions of cells that can synthesize functional protein.
It should be noted that we are still in the early stages of developing gene therapy and there is still more work to do before reaching full potential.
If you would like advanced information of gene therapy, recent molecular biology and molecular genetic text books usually have very good information. You can also visit http://www.genetics.com.au/ which has decent information.