General Genetics/Genetic Principles

How a living organism is built and functions is determined and governed by genes. Understanding how genes work may enable researchers to:

• detect and cure genetic illnesses.
• determine an organism's features and behaviors.
• create a new organism.

The relationships between genes and features are very complex. Currently, we are unsure if it will ever be possible to change only one feature of an organism by changing one or a set of genes. If features are able to be genetically altered, there is a likelihood that any attempt may accompany other changes. The other changes could be small and/or ignorable however. Some changes are gradual, while changes in gene expression can result in rapid transformations in the physiological state of an organism.

Gregor Mendel and Peas

Gregor Mendel was an Austrian monk. He is credited as the father of modern genetics. While planting and harvesting pea plants on his monastery he noticed patterns of traits in pea plants. Most pea plants turned out to have green pods, some had yellow pods. Some had yellow seeds and while others had green seeds. Stem length, petal color, pod shape, location of flowers all these seemed to exhibit a pattern of inheritance.

Mendel went on to breed pea plants to see how these traits acted. Through these experiments Mendel created 3 laws that govern how traits are passed on from parents to offspring.

Mendel's Laws

Law of Dominance - In a cross between contrasting traits only 1 appears in the F₁ generation this is the dominant trait; the other is recessive

Law of Segregation- During gamete formation the 2 traits responsible for each trait separate so each gamete has only 1 gene for each trait

Law of Independent Assortment- when dihybrid plants are crossed the factors for 1 trait are distributed separately from other traits so that one can find all these changes

Chromosomes, alleles and Mendel’s law: the behavior of homologous chromosomes during meiosis can account for the segregation of the alleles at each genetic locus to different gametes. The alleles for 2 or more genes located on different chromosomes. In Mendel’s experiment, the segregation and the independent assortment during meiosis in the F1 generation give rise to the F2 phenotype ratio observed by Mendel.

Law of Dominance

It is when crossing two contracting character traits, one of the character traits will be masked of or will not show which is recessive and the other will be dominant.When Mendel crossed breeds two pea plant with contracting height,one being tall(TT) and the other being short or dwarf(tt). What he found is that all the the first generation(F1) where all tall.