Another aspect of genetics is the study of the influence of heredity on behaviour. Many aspects of animal behaviour are genetically determined and can therefore be treated as similar to other biological properties. Galton became the first to use twins in genetic research and pioneered many of the statistical methods of analysis that are in use today.
The importance of mutations that give rise to color vision is that they immediately allow us to appreciate how a change in a single gene can give rise to a fundamental change in our mind--in the way we perceive the world. If you are male, you may want to test your color vision.
This common, sex-linked defect is explained by the close proximity of the two genes on the X chromosome. A much rarer condition, total colorblindness or rod monochromacy OMIM must be caused by mutations in a gene common to all cones. Huntington's disease is a poor example to illustrate behavioral consequences of mutations.
Huntington's disease or Huntington's chorea, from the dance-like movements made by some patients is a dominant disease: It is passed on because individuals who carry the gene usually do not realize they are affected until middle age, although onset of symptoms can vary by more than 50 years.
Both symptoms and post-mortem examination of brains indicate that brain damage occurs most severely in the basal ganglia, thus first affecting motor behavior but eventually affecting cognition and death.
Even though a single gene is involved, the age of onset and time course of the disease varies greatly. About 30, Americans have HD. Dominant diseases usually involve a gain of function, rather than the mere loss of a protein. Indeed, the discovery of the gene for Huntington's disease, after a long and much publicized search, shows that the disease results from the expansion of a tract of repeated CAG nucleotides at the beginning of the coding region of the gene.
The age of onset decreases as the tract length increases: The triplet CAG codes for the amino acid glutamine, so the triplet expansion means that the protein will have a longer than normal tract of glutamine at its N terminus.
It is a giant protein of kDa, and, surprisingly, it is found in virtually every type of cell examined. Huntingtin is an essential protein--when it is eliminated in mice by gene targeting, the mice die as embryos. Is function is unknown.
Although the evidence is still incomplete, it looks as though huntingtin proteins that have extra long glutamine terminals tend to aggregate with one another and possibly with other proteins.
This has been demonstrated in vitro by attaching glutamine tracts of different lengths to green fluorescent protein GFP. In normal brains huntingtin is distributed throughout neurons, perhaps being enriched in nerve terminals, but also being observed in dendrites and cell bodies and as stated before it is in non-neural cells as well.
At first it was thought that these inclusions were causing cell death, but other work suggests not. In cultured rat striatal neurons, mutant Huntingtin induced degeneration in cultured striatal neurons but not in hippocampal neurons. Neurons degenerated as a result of apoptosis, and cell death could be prevented by anti-apoptotic compounds and neurotrophic factors.
It will be fascinating to see how this story develops, but it is highly unlikely that we will find any special role for huntingtin in motor behavior or in cognition-- in the sense that the color pigments play a special and essential role in color vision.
Unforeseen breakthroughs in molecular technology are revolutionizing the study of genes and behavior. In many areas of scientific advancement, predictions of future achievements are often overstated. For example, artificial intelligence vastly underestimated the complexity of the mental processes it sought to simulate.
However, in molecular biology, progress has been faster than predicted. Much of the progress has resulted from the discovery, and then rapid harnessing, of potent molecular mechanisms.Human behavior is determined by a combination and interaction of heredity and environment.
Such an interactionist approach to the nature versus nurture controversy is a theoretical compromise, but one which has logic and empirical validity to recommend it. In some situations, genes play a larger role in determining your behavior; in other situations, environment plays a larger role in influencing your behavior.
If you had a whole different set of experiences over your lifetime your genes may be expressed in different ways, and you may behave differently than you do now.
Like heredity, environment also has been found to play a very important role in determining the behaviour and personality development of an individual. The environmental influences are those which act upon the organism at the earlier stages of development, i.e., before and also after birth. Heredity can influence behavior in many ways, with one such example being how color is processed in the brain; color blind people perceive the world in an alternative way, which can cause changes in how everyday tasks are approached.
Behavior is not only influenced by biology through the mechanisms of anatomy and physiology. Heredity also plays a major role in the emergence and control of behavior. The study of heredity, genetics, particularly its subfield behavioural genetics, is crucial in understanding the relationship between heredity and behavior.
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The biological or psychological characteristics which are transmitted by the parents to their off-springs are known by the name of heredity. Heredity is, in other words, a biological .