Tag Archives: biology

The Genetics Behind Huntington’s

Huntington Disease is a rare genetic condition that most people have never even heard of unless a) they study it b) they personally know someone with the disease or c) they are a fan of House. Luckily for me only a) and c) apply in this situation. However, I believe Huntington’s like a variety of other diseases is something the public needs to be educated about because awareness really is the greatest way to inspire research into any field.

As autosomal dominant disorder this makes Huntington’s especially dangerous because as a dominant trait a person only needs one affected allele to develop the disorder. Were the trait recessive such as the trait for hemophaelia, for example, then the likelihood of having Huntington’s is significantly lowered. When a trait is autosomal this means that it is no carried by any of the sex chromosomes (X or Y), rather is carried by any of the other 22 chromosomes the human body has. In Huntington’s the gene affected is located on chromosome 4, specially on the p (upper, shorter) arm.

huntington

 

 

 

 

 

 

 

 

 

 

 

The symptoms of Huntington’s has already been discussed on a previous post on basal ganglia disorders; however, in summation it results in damage to the striatum and cerebral cortex causing changes in personality including mood swings, involuntary movements known as hypokinesia and eventually dementia. As is common with most genetic disorders, the symptoms do not appear until adulthood. In Huntington’s the symptoms usually arise around mid-age, but unfortunately it can arise earlier than our 30s or 40s if unlucky. Once symptoms start appearing the person usually has about another 5 to 15 years until death. The age at which symptoms appear directly correlates with the genetics behind the abnormal gene.

Huntington’s is part of numerous diseases including varies ataxias and fragile X syndrome that result due to trinucleotide repeat. Specifically, Huntington’s is due to a repeat of the CAG trinucleotide. Normal alleles carry about 10 to 35 copies, but those suffering from Huntington’s and various other neurodegenerative diseases have more than 40 repeats. People with around 60 repeats with develop Huntington’s around the age of 20. These repeats in CAG result in the production of a “mutant protein” that eventually fill the striatum and cerebral cortex causing degeneration and ultimately death of these brain cells. In healthy individuals the gene involved in Huntington’s encodes for a large protein known as huntingtin (Htt), which when normal enhances the production of a protein (BDNF) necessary for the survival of the cells in the striatum and cerebral cortex.

Stay tuned for a post later this week on current experimental treatment on Huntington’s! Thank you for reading :)

Citation:

Cummings, Michael. “Genetics of Behavior.” Human Heredity: Principles and Issues. 9th ed. Belmont: Brooks/Cole, 2011. 405-06. Print.

Basic Nutrition: Essential Nutrients and Biosynthesis

Our bodies rely on food for energy but also for biosynthesis. Biosynthesis is the production of complex molecules within living organisms or cells; a process necessary for self-maintenance. For example, the synthesis of protein from neuropeptides. Two necessary precursors for biosynthesis are organic carbon (such as from sugar) and organic nitrogen (such as from amino acids). For a diet to be sufficient, therefore, it must supply chemical energy, organic molecules and finally essential nutrients.

For energy, animals ingest and digest nutrients such as carbohydrates, proteins and lipids to get enough ATP necessary for cellular respiration and energy storage. Essential nutrients are ingested as precursors to complex molecules and as minerals and vitamins. Unlike complex molecules, essential nutrients cannot be synthesised from raw materials. Thus, they must be ingested.

Amino Acids and Fatty Acids

Four types of essential nutrients exist: amino acids, fatty acids, vitamins and minerals. Approximately, half of the 20 amino acids are required for humans including: methionine, valine, threonine, phenylaline, leucine, isoleucine, tryptophan, lysine and histidine. Meat, fish, poultry, dairy products are considered complete proteins because they contain all essential amino acids. However, vegans and vegetarians or even meat-eaters can get all their essential amino acids by eating a full diet consisting of beans, legumes, nuts, seeds and vegetables. Insufficient amounts of amino acids causes protein deficiency, which can be severely detrimental to healthy development. Therefore, if you stop eating meat, it is important to make sure you are eating a diet that contains all your essential amino acids.

food1

Essential fatty acids are also required. Only two are known to be essential for human survival: alpha-linoleic acid and linoleic acid. Alpha-linoleic acid is a long-chain omega-3 fatty acid and is high in food such as salmon, tofu, shrimp, flax seeds and walnuts (fish, seeds, grains and vegetables). Linoleic acid is a long-chain omega-6 fatty acid and is found nuts, grains, cereals and poultry. Insufficient amounts of omega-3 and omega-6 contributes to impaired cellular functioning and heart disease.

Vitamins and Minerals 

The final two essential nutrients are vitamins and minerals. Vitamins come in two, organic forms: soluble and water-soluble. Fat-soluble vitamins are found in fatty foods such as animal products, vegetable oils, etc. They include vitamin A, D, E and K and are stored in our liver and fatty tissue. Deficiency in certain vitamins cause different issues (a future post will discuss this in more detail). Water-soluble vitamins, on the other hand, are not stored in the body and so need to be consumed more frequently. These means that when we urinate, these vitamins leave our body. Fortunately, that means it is hard to consume too many water-soluble vitamins. Too many fat-soluble vitamins can cause toxicity. Water-soluble vitamins include vitamin C, B and folic acid and can be found in foods such as fruit, vegetables (especially greens) and grains. As water-soluble vitamins are sensitive to heat and air, boiling can destroy the vitamins. Foods high in fat-soluble vitamins are far more durable.

Minerals on the other hand are inorganic and include calcium, iron, phosphorus, magnesium, sulphur, sodium, potassium and chloride. Minerals also come in two forms: macro or major minerals and trace elements. Macrominerals include electrolytes and the body stores about 5 grams of each one on hand. In order to stay healthy, a person to consume about 100mg a day to maintain the 5 gram store and equalise the loss. Trace elements are found in much smaller quantities, hence their name and include iron, zinc, iodine, selenium, copper, manganese, fluoride, chromium and molybdenum. Minerals are essential because they serve as reinforcers for bone growth, strong teeth, maintaining homeostasis and synthesising energy from food. A great source of minerals is from plants such as fruits, vegetables and nuts as they get minerals directly from the soil they grow in. Grains, meats, cereals, dairy, etc. also contain minerals but in a diluted amount due to processing or because they have already been used by the animal itself.

All in all, a proper diet needs to incorporate all essential nutrients for proper health and functioning.

Bibliography

Campbell, N. A., & Reece, J. B. (2008). Animal Nutrition . Biology (8th ed., ). San Francisco: Pearson, Benjamin Cummings.

Rinzler, C. A. (2006). Nutrition for Dummies (4th ed.). Indianapolis, IN: Wiley Pub.

Vitamins and minerals . (2012, November 26). . Retrieved June 24, 2014, from http://www.nhs.uk/conditions/vitamins-minerals/Pages/vitamins-minerals.aspx