Sierra College Department of Biological Sciences

Discover the Biological Sciences

The introductory information for this site has been contributed as a joint assignment by students in Bio. Sci. 10.

Genetics - Mendelian Genetics

By: Veronica Mendez

1. Biological field or sub-topic: Mendelian Genetics

2. Define field or sub-topic: Two principles developed by a European Monk, Gregor Mendel, explaining the inheritance of genetic characteristics between a parent generation and its children . He was able to develop these principles through the research he accomplished with pea flowers.

3. Describe in more detail the breath and depth of what could be studied or learned within this topic?

Gregor Mendel was a European monk that spent his days at the monastery out in the garden growing a familiar plant from his boyhood days, pea flowers. All this work was not just for fun, he was curious to see if there was a way to determine the genetic characteristics to the offspring of a sexually producing parent generation. Since he was familiar with pea plants and they were easy to reproduce, he was able to see the characteristics of the flowers over many generations.

In the parental generation Mendel began with two different colored pea flowers: white and purple. Other than a difference in color, the two also varied in pod shape, pod color, stem length, flower position, seed color, and seed shape. These physical characteristics are known as the plants phenotype. These true-breeding plants were ideal for the research performed because Mendel knew that when the flowers self-pollinated, one hundred percent of the offspring would be identical to its parent. So, when he cross-bred the two plants he knew that the next generation would possess its parents genetic characteristics, he just did not know in which order. By studying these characteristics over the generations he was able to come up with the Principle of Segregation and the Principle of Independent Assortment.

Through his research, Mendel hypothesized that organisms have alternative forms of genes, or alleles, and it is the genes that determine an organisms characteristics. Children get one gene from each parent for the same characteristic, they may be the same or different. If the alleles are different, only the dominant allele will be exhibited. The recessive allele will stay dormant. It is the way these genes pair up that determines the genetic code of an organism, which is also known as an organisms genotype. With this knowledge, Mendel’s Principle of Segregation will be easy to comprehend. It states, by the book, that pairs of alleles segregate during gamete formation; the fusion of gametes at fertilization creates allele pairs again.

All the information so far can be deduced through a monohybrid cross, meaning one characteristic acting independently through two cross-bred plants. What happens when one essential part of the plant has two different characteristics? In Mendel’s studies one of his plants had a round yellow seed, and one had a green wrinkled seed. The big question was would the two characteristics be passed on after the cross breeding as a pair or will they act independently? His question was soon answered after a few generations of his plants and he was able to develop the Principle of Independent Assortment. It states, by the book, that each pair of alleles segregates independently of the other pairs during gamete formation.

4. Focusing on one major concept, principle, or group of organisms, describe its importance, relationships, functional aspects, or otherwise explain it in more depth as seems important to you and others in class.

With these principles were are able to accurately determine, of we know which alleles are dominant and which are recessive, we can accurately determine the phenotype and genotype of our offspring. We can determine the percentage that your children have a genetic mutation you or your significant other might have, whether it be good or bad. With this knowledge farmers and other animal breeders can pick out the characteristics they want and find the right mate for that animal to produce offspring to their desirability. The same can be done with plants. These are extremely helpful principles in many aspects of life.

5. In studying and discovering more about this topic, what was the most interesting aspect, fact or some other piece of information that you have learned?

I love the fact that a some what big and scary process can be so easy to use, that is on a small scale.

6. References:

Campbell, Neil, Reece, Jane, and Eric Simon. Essential Biology: Second Edition. San
Francisco: Pearson, 2004.

Jurmain, Robert, Kilgore, Lynn, and Wenda Trevathan. Introduction to Physical
Anthropolgy: Tenth Edition. Belmont: Thomas Wadsworth, 2005.

Bailey, Regina. “Genetics Quiz: Mendelian Genetics.” 2007.

< <> >.

O’Neil, Dennis. “Basic Principles of Genetics: an Introduction to Mendelian Genetics.”
Palomar College. 31 July 2007. < <> >.

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