Lecture 20 - Disorders Due to Chromosome Numbers

Lecture 20 - Disorders Due to Chromosome Numbers - Lecture...

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1 Disorders due to Chromosome Numbers Biology 1F25 for Biology Non-Majors Lecture 20 Background Reading Textbook, Chapter 18. The People Who Prepared This Lecture Harry Peery Alan Castle Chris Burke • Born in 1965 in New York State. • Parents were told by doctors to institutionalize him as he would never amount to anything. • They said he would always be mentally retarded. • They said had a form of idiocy and would always be a drain on family resources.
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2 Today • It is the doctors who had the idiocy – Chris Burke is an actor, he is very self-sufficient and has a very good income. He speaks all over the world. • Here he is with his band. What Did Chris Burke Have? Interlude: Cell Cycle and Mitosis and Meiosis Types of Cell Division Cell Cycle • There are 4 stages in the life cycle of a cell –G 1 stage is for the first gap between the end of telophase and the beginning of DNA synthesis. G 0 is a G 1 gap that never ends. – S stage is for synthesis of DNA (the DNA replicates) –G 2 stage is for the second (and very short) gap between S stage and beginning of mitosis – M stage is for mitosis and results in two daughter cells. Interphase
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3 Cell Cycle •G 1 , S, and G 2 are collectively called interphase. What happens in interphase is invisible. • Mitosis is the visible stage of the cell cycle and results in the formation of two daughter cells. Mitosis Each daughter cell ends up with the same amount of DNA and same amount of chromosomes as the parent cell before the beginning of mitosis. Takes place in all cells in a mammal at some stage of their development. At the end of Mitosis • There is no reduction in the amount of DNA from the parent cell. • The number of chromosomes remains the same. Each chromosome at the beginning of prophase has two chromatids At the end of telophase, each daughter cell has only one chromatid (which is now called a chromosome) Meiosis • Occurs only in ova or sperm and only after several mitoses.
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4 At the end of Meiosis • The number of chromosomes is reduced by half. • There is a reduction by half in the amount
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This note was uploaded on 06/10/2008 for the course BIOL BIOL-1F25 taught by Professor Peery during the Spring '08 term at Brock University.

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Lecture 20 - Disorders Due to Chromosome Numbers - Lecture...

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