Wk 5 Lec 1

Wk 5 Lec 1 - Whatwerewetalkingabout? Mistakesinmeiosis...

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What were we talking about? Mistakes in meiosis Down syndrome Abnormal numbers of sex chromosomes Chromosome alterations
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Chapter 9 Patterns of Inheritance
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Introduction Attempts to explain inheritance date back at least to ancient  Greece Hippocrates, suggested an explanation called pangenesis  According to this idea, particles called pangenes travel from  each part of an organism’s body to the eggs or sperm and are  then passed to the next generation  Moreover, changes that occur in various parts of the body  during an organisms’ life are passed on in this way  Aristotle rejected this idea as simplistic, saying that what is  inherited is the potential to produce body features, rather  than particles of the features themselves 
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Introduction  By carefully tracking inheritance patterns in  ornamental plants, biologists of the early  nineteenth century established that offspring  inherit traits from both parents  The favored explanation of inheritance then  became the “blending” hypothesis, the idea that the  hereditary materials contributed by the male and  female parents mix in forming the offspring in such  a way The “blending” hypothesis was finally rejected  because it does not explain how traits that  disappear in one generation can reappear in later  ones 
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Mendel’s Contribution Mendel was a monk who lived and worked in an abbey in Austria Mendel correctly argued that parents pass on to their offspring discrete  heritable factors  He stressed that the heritable factors (genes) retain their individuality  generation after generation Mendel’s theory differed from both pangenesis and the blending  hypothesis Mendel was a good biologist who was also strongly quantitative,  therefore much of his work has stood the test of time, because it was done  very precisely He studied garden peas which are easy to grow and available in many  readily distinguishable varieties Mendel had success because 1. Focused on a few traits (7) 2. Documented and quantified results 3. Chose the garden pea  Pisium sativum   as his subject
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Mendel’s Experimental Design Mendel was able to exercise strict control over  plant matings  The petals of the pea flower almost completely 
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Wk 5 Lec 1 - Whatwerewetalkingabout? Mistakesinmeiosis...

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