Gregor Mendal

Gregor Johann Mendel, an Austrian monk, discovered the laws of inheritance. Mendel was born the 22^nd July 1822 in Hynice, Czechia. He was a scientist, teacher and monk. Gregor Mendel’s parents were farmers and growing up on a farm Mendel became highly interested in gardening.

Seeing Mendel’s obvious talent his parents struggled to pay his tuition to high school and, later, the Olmutz Philosophical Institute. Unfortunately, they were unable to pay his university fees so instead he joined Augustinian monastery teaching part time at a high school. In order to teach full time Mendel was required to sit exams which he failed on two occasions. Gregor Mendel was also assigned to work as a chaplain for a hospital; he found it infuriating and far too difficult and later decided to resign to the monastery where he had taken to tending the garden.

Another reason he chose to join the monastery is due to his financial troubles, joining meant that he could carry on his studies without having to worry about cost. He later proceeded to the University of Vienna where he chose to study physics, botany and chemistry. After finishing university he returned to the monastery and became a teacher of natural sciences at the Technical School at Brno.

In the 1856 Gregor Mendel, began to experiment with peas, his main purpose of his investigation was to develop an understanding of how any organism passes physical characteristics or traits from one generation to the next.

Gregor Mendel’s Experiments

Mendel focused on certain traits of the pea plant, such as height, colour of seeds and the shape of the pea seeds. He carefully organised which plants cross pollinated in order to track which characteristics were passed between generations. To cross pollinate Gregor Mendel took the pollen from one pea plant and placed it onto another which he had selected.

For Mendel’s first experiment he took the pollen from one short stemmed pea plant and placed it on another selected short stemmed plant; the outcome was as expected, the offspring were all short stemmed pea plants. Mendel called these “true breeders”; the term was given because all of the offspring were the same as the previous generation.

For his second experiment, he completed the same experiment but with long stemmed pea plants. Taking the pollination of one long stemmed plant and placing it on another, like most people Mendel believed the result would be long stemmed pea plant offspring, but, he was wrong. Some of the offspring were tall, however some of the offspring were short stemmed.

After completing more experiments Gregor Mendel eventually discovered some tall stemmed are “true breeders” producing only tall offspring, while others were not “true breeders” as they produced mixed height offspring.

To develop his understanding further Mendel began more experiments taking pollen from tall stemmed pea plants (true breeds) and pollinating short stemmed plants (also true breeds). He did this in order to find out which trait would be passed onto the next generation. Surprisingly thought he result of the offspring were all tall stemmed pea plants, he called this generation the F1 generation.

The short stem trait appeared to have disappeared. Mendel then proceeded to cross pollinate the F1 generation with other pea plants in the same F1 generation, by doing this the short stemmed pea plant trait reappeared creating some short offspring.

Gregor Mendel’s Discovery

By doing this Gregor Mendel discovered that every plant has two genes for each trait not one. This meant that “true breed” short stem plants have two short genes where as a “true breed” long stem plant has two long genes and cross pollinated short and long stem pea plants produce offspring with one long and one short gene.

Later Mendel discovered that some genes are more dominant than others. When there are two mixed genes (long and short) the most dominant gene will determine how the plant will grow. The gene which is not dominant is known as recessive. In pea plants the dominant gene is the tall gene or trait, while the short gene is recessive. Although the offspring may have been a tall stemmed pea plant it can still carry the short recessive gene which may appear in future offspring.

Gregor Mendel’s Hypothesis

            Gregor Mendel then later went on to develop a hypothesis about inheritance and how genes are passed from one generation to the next. The hypothesis which is still used today by scientist states that a pea plant or any other organism has two genes for each trait, creating a gene pair.

            During any reproduction process, each parent can only pass on one gene from each trait or gene pair to their offspring. This therefore means that the offspring will inherit one gene from each parent creating a new gene pair.

Gregor Mendel’s Gene Codes

When writing gene pairs scientists use a mixture of uppercase and lowercase letters (TT), (Tt), (tt). Capital letters represent the dominant genes while the lowercase letters represent the recessive gene.

In Mendel’s experiments with pea plants he coded the “true breed” tall stem pea plants as (TT), this indicates that the gene pair for the height trait are both dominant tall genes, while the code for “true breed” short stem plants is (tt) indicating that the height trait is composed of two recessive short genes.

When cross pollinating a short and a tall stem plant; the result would be (Tt); one tall dominant gene with one short recessive gene. He then later cross pollinated two (Tt) plants, this produced mixed results, and some plants received both (TT) and both (tt) genes, while others still came out with (Tt). All plants with combinations (TT), (Tt) or (tT) were tall as (T) (the tall gene) is the most dominant gene.

From this Mendel was able to work out the chances of having a small stemmed plant when cross pollinating two (Tt) pea plants. The results were three out of four or 75% chance that the offspring will be tall and one out of four chances or 25% chance of the offspring being short.

Dominant and Recessive

            Nearly all gene pairs have a dominant gene and a recessive gene; however this is not always the case. Instead of one gene dominating another, it is highly possible for genes to produce mixed result. For example Four o'clock flower. When you mix a red (RR) flower with a white (WW) flower, the result is (RW), however, the flower is neither the red or white, there is no dominant gene. The result is a mixed pink flower.

            Before passing away on January the 6^Th 1884, wrote “I am convinced that it will not be long before the whole world acknowledges the results of my work”; which as he predicted was true, his discovery was rediscovered thirty-five years later creating a foundation for modern genetics.