Gregor Mendel's Alleles: Garden Pea Plants

Gregor Mendel was born in 1822. He was an Augustinian monk and is known as the father of genetics, who carried out numerous crosses in the mid 1800s. He worked mainly on garden pea plants where his works led into two laws. Mendel’s law of segregation, also his first law states that,

• Inherited characteristics are controlled by pairs of factors now known as alleles

• These factors segregate at gamete formation so that only one factor is carried in each gamete.

Mendel predicted that alleles which are different forms of the same gene occurred in pairs which meant cells were diploid and some process now known to be meiosis resulted in the number of alleles being halved. When two flowers of different colours, are crossed they produce one colour

The easiest way to explain how to develop an F1 hybrid is to take a plant with a good habit but a poor flower colour and another plant of the same type which has a poor habit but a good flower colour. These are then pollinated in isolation year after year until such time the same identical plants appear. This is then known as the pure line. If the breeder now takes the pure line of each of the two original plants and cross pollinates them by hand, the result is known as an F2 hybrid. Plants are grown from the seed produced and the result of this pollination should have the combined traits of two parents.

Conventional plan breeding has a huge impact on agricultural productivity and is still a very important tool, but it has its limitations. Breeding can only be done by two plants that can sexually mate with each other. This limits the new traits that can be introduced and any undesirable traits can also be transferred across with the good traits. The benefits of the F1 seed are there is more uniformity of colour, a better yield and size but while the plant breeders control the inbred lines this would leave the seeds more

They have an absence of a membrane-enclosed nucleus therefore they are prokaryotes. They are normally small single celled and usually reproduce asexually and under ideal conditions can reproduce every twenty minute. They are classified according to their shape, rod, round, and spiral shaped. Bacteria may be autotrophic meaning that it can make its own food. Heterotrophic means it takes in food and this can be split into saprophytes which take its food from dead sources, and parasitic which takes its food from a living host. Good bacteria can make food such as purple sulphur bacteria while bad bacteria can cause typhoid and