GENETIC DISORDERS
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Transcript of GENETIC DISORDERS
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GENETIC DISORDERS
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____________________________ –change in a gene resulting in change in genetic information
• may be spontaneous or caused by a mutagen
• _____________________ mutations are usually not noticed
• ______________________________ mutations are more severe
• Not all mutations are bad!
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______________________• Misplacement, insertion or deletion of one base
pair • May result in incorrect amino acid• May result in shift of reading frame
Congenital Defects: Visible at birth(club foot, spina bifida, congenital heart defects)Caused by environmental factors (FAS, German measles)
Inherited Sickle Cell Anemia, Cystic Fibrosis
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__________________• Part of chromosome is
flipped around 180° from its normal orientation.
• Happens when chromosome breaks occur.
• Broken piece may reattach, but not necessarily in the same orientation as before
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__________________• Detachment of a segment of a
chromosome, and reattachment to another non-homologous chromosome.
• Some genes wind up on a completely different chromosome
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ANOMALIES OF CHROMOSOME NUMBER
• ________________ is common in plants
• Gametes don’t reduce chromosome #
• Result in cells with multiple copies of the genome
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ANOMALIES OF CHROMOSOME NUMBER
• __________________ – more common in humans
• Usually lethal before or shortly after birth
• Monosomic and Trisomic
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_________________________
• Occurs when homologous chromosomes fail to separate after synapsis
• Most nondisjunction events are lethal to the fetus
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_______________________
• Results from a third copy of chromosome 21
• Called a trisomy• Individuals have 47
chromosomes in every body cell
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SEX CHROMOSOME NONDISJUNCTION DISORDERS
______________________________• Occurs when nondisjunction causes a gamete
to have a missing sex chromosome (X O)• Sterile females• 1 in 10 000 live births
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SEX CHROMOSOME NONDISJUNCTION DISORDERS
________________________________• Genotype of XXY (extra sex chromosome)• Sterile males, breast development• 1 in 800 live births
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SEX CHROMOSOME NONDISJUNCTION DISORDERS
½ ½
½
gamete lacking a sex chromosome
XO ¼ Turner’s syndrome
YO ¼ Will not survive(LETHAL CONDITION)
½
gamete formed from nondisjunction
XXX ¼“super female” usually normal
XXY ¼ Klinefelter’s syndrome
XYX Y
O
XX
XX