Bio - Lecture 12

Bio - Lecture 12 - several times Deletion: -Another reason...

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Sheet1 Lecture 12: Chromosomes Sex Determination -Humans have 23 pairs of chromosomes -Autosomes are those chromosomes that both males and females have in common ->There are 22 -Sex chromosomes are those that determine the gender of the individual ->There are two -In humans, XX is female and XY is male ->The inactive X chromosomes in females is a Barr body X-linked Inheritance -This is when a recessive allele is on the X chromosome which may cause a disorder -Males are affected more than females -Fathers cannot transmit this disorder to their sons -Examples of this type of inheritance are hemophilia, color blindness and fragile X syndrome ->X syndrome is a rare disorder that only affects males and includes mental retardation. Changes in chromosome structure: -Sometimes the actual structure of achromosome changes which may result in genetic diseases or have no effect -This may occur through duplications -This is when genes are duplicated
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Unformatted text preview: several times Deletion: -Another reason chromosomes structure may be affected is through deletions -THis is when parts of the chromosome are deleted Inversion: -Another reason chromosome structure may be affected is through Inversion -HTis is when parts of the chromosome are switched Translocation: Another reason chromosome structure may be affected is through Translocation -This is when non-homologous chromosomes recombine Changes in number: -CHromosomes normally separate during Meiosis -If they do not, it is called nondisjunction and results in aneuploidy -Monosomic (those who lack a chromosome) do not survive development -Most trisomics (those who have an extra chromosome) also do not survive development ->Also called polyploidy ->Some survive, but have developmental defects -If aneuploidy occurs with sex chromosomes, the abnomalities are generally not fatal -There are several manifestations of this nondisjunction Page 1...
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This note was uploaded on 05/06/2008 for the course BIOL 121 taught by Professor Lopez during the Fall '07 term at Lansing.

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Bio - Lecture 12 - several times Deletion: -Another reason...

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