Nursing Preparation Study Guide

Nursing Preparation Study Guide A small or even minute difference in the genes of two organisms would mean that the two organisms have different genotypes. Genes are hereditary and the genetic information contained is passed down from parents under control of specific molecular mechanisms. The genes or genetic information therein would affect or control the representation of the phenotype. The genes define the trait or feature of the organism while the phenotype is the observable demonstration or expression of that trait. For example, if a mouse has a white color, it can be said that the genes defines that the mouse would be white and the phenotype is the white color that is observable. The genotype determines the phenotype, but the phenotype is also affected by external factors, such as environmental factors. A set of genotypes mapped to a set of phenotypes is called a genotype-phenotype map. The genotype is the largest influence on an organism’s phenotype, but is not the only factor; this is why identical twins that share the same genotype would still not have the same phenotypes. They may share identical genomes and their phenotype may even be quite similar, but it cannot be the same (which is why parents and close friends are able to tell them apart). It is due to their phenotype, or the expression of their genetic makeup as contained in their genotype, would not be the same. The term phenotype plasticity is used to describe the extent to which the genotype of an organism determines its phenotype. An organism with weak or little phenotype plasticity would be highly determined more by its genotype and less by environmental factors. An organism with high phenotype plasticity would have its phenotype more affected by environmental factors than by its genotype. A good example of an organism with high plasticity whose phenotype is more dependent on its environment than its genotype is the larval newt. The larvae grow larger tails and heads relative to their body size when it notices the presence of their natural predators, such as the dragonfly. Phenotype canalization is a term used to describe the extent that an organism’s phenotype draws conclusions about the organism’s genotype. An organism with a canalized phenotype would rarely be affected by changes in its genotypes. If canalization is absent, very minor changes in the genome would result in immediate changes in the resulting phenotype. Heredity: Genes and Mutation All the genetic material that tells our cells which jobs they are assigned is stored in our DNA. When complex creatures like humans reproduce, our DNA is copied and combined with our mate’s DNA to create a new genetic sequence for our offspring. This information is stored in our genes and encoded in DNA base pairs through different combinations of the chemical groupings adenine, thymine, guanine, and cytosine (represented by A, T, G, and C, respectively). Each gene covers a small portion of our DNA, and is responsible for creating the protein for which that particular section of DNA holds instructions.

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