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The Monk and his peas


Date: 2015-10-07; view: 409.


An Austrian monk, Gregor Mendel, developed the fundamental principles that would become the modern science of genetics. Mendel demonstrated that heritable properties are parceled out in discrete units, independently inherited. These eventually were termed genes.

Gregor Mendel, the Austrian monk who figured out the rules of hereity.

 

Mendel reasoned an organism for genetic experiments should have:

1. A number of different traits that can be studied

2. Plant should be self-fertilizing and have a flower structure that limits accidental contact

3. Offspring of self-fertilized plants should be fully fertile.

 

Mendel's experimental organism was a common garden pea (Pisum sativum), which has a flower that lends itself to self-pollination. The male parts of the flower are termed the anthers. They produce pollen, which contains the male gametes (sperm). The female parts of the flower are the stigma, style, and ovary. The egg (female gamete) is produced in the ovary. The process of pollination (the transfer of pollen from anther to stigma) occurs prior to the opening of the pea flower. The pollen grain grows a pollen tube, which allows the sperm to travel through the stigma and style, eventually reaching the ovary. The ripened ovary wall becomes the fruit (in this case the pea pod). Most flowers allow cross-pollination, which can be difficult to deal with in genetic studies if the male parent plant is not known. Since pea plants are self-pollinators, the genetics of the parent can be more easily understood. Peas are also self-compatible, allowing self-fertilized embryos to develop as readily as out-fertilized embryos. Mendel tested all 34 varieties of peas available to him through seed dealers. The garden peas were planted and studied for eight years. Each character studied had two distinct forms, such as tall or short plant height, or smooth or wrinkled seeds. Mendel's experiments used some 28,000 pea plants.

 

 

 

 

 

 

Some of Mendel's traits as expressed in garden peas.

Mendel's contribution was unique because of his methodical approach to a definite problem, use of clear-cut variables and application of mathematics (statistics) to the problem. Gregor Using pea plants and statistical methods, Mendel was able to demonstrate that traits were passed from each parent to their offspring through the inheritance of genes.

Mendel's work showed:

1. Each parent contributes one factor of each trait shown in offspring.

2. The two members of each pair of factors segregate from each other during gamete formation.

3. The blending theory of inheritance was discounted.

4. Males and females contribute equally to the traits in their offspring.

5. Acquired traits are not inherited.


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