3.3_Inheritance - In the last presentation, we looked at...

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In the last presentation, we looked at cellular reproduction and introduced the process of meiosis or production of gametes. We now look at the genetic implications of sexual reproduction and the inheritance of traits. This will reveal the distinct benefits of sexual reproduction in terms of producing biological diversity in contrast to asexual reproduction. 1
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We’ll first overview Mendel’s work from the 19 th century which laid the foundation for the field of genetics and was built upon by scientists during the 20 th century leading to contemporary theories pertaining to molecular genetics. And then, we will relate the principles of inheritance discovered by Mendel to our understanding of chromosomes. 2
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I’ll let Mendel’s own words (here translated from German to English) speak for his perspectives of his work when he published his important paper on the inheritance of traits in pea plants. Mendel was a brilliant, yet humble, scientist. His paper was published in an obscure journal and it’s significance remained hidden for decades. 3
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4 The work of Gregor Mendel in the 1860’s laid the foundation for our understanding of inheritance and it’s a fascinating example of how science progresses. Mendel used pea plants to study the passing on of traits from parental plants (abbreviated P) to offspring (abbreviated F standing for filial). Each filial generation is designated with subscripted number. He used careful techniques of artificial pollination and tracking of offspring traits such as flower color, pea texture and color to develop two generalizations now called scientific laws. Recall that laws are statements that describe patterns of nature that we consistently observe. Even though Mendel didn’t know about the molecular nature of genetics, he was able to recognize principles that are consistent with our contemporary understanding of genetics. We will examine his laws, the chromosomal basis of these laws and some variations as well. Ironically, his work was largely ignored by the scientific community until after his death. Most scientists thought that parental traits were blended in offspring which was consistent with many observations. Mendel himself was doubtful of how applicable his ideas were in many cases of inheritance. It wasn’t until the early 1900’s, that scientists came up with the chromosome theory of inheritance and Mendel’s laws became widely accepted.
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white flowers in garden peas disappear in the first filial generation and reappear in the second filial generation. Mendel used monohybrid crosses to explore this mystery. A monohybrid cross refers to fertilizing two true breeding parents for a single trait. True breeding refers to the parental plants, when self-fertilized, produce only offspring that exhibit the same trait such a specific color of flower. 5
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This note was uploaded on 01/29/2012 for the course BIOL 212 taught by Professor Rockhill during the Spring '08 term at Seattle Central Community College.

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3.3_Inheritance - In the last presentation, we looked at...

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