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Lecture 21

BIOL 1201 Lecture Notes - Lecture 21: Y Chromosome, Aneuploidy, NondisjunctionPremium

Biological Sciences
Course Code
BIOL 1201
Moroney, James

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BIOL 1201- Lecture 21-Pedigree and Gene Expression
Pedigree Map
Squares are males
Circles are females
Half filled= carriers
Dark= infected
In females, one X chromosome isn’t active since there are two
Gene is on the Y chromosome
All females are normal (XX,lack trait)
All males have the trait (XYt)
Y chromosome is small, room for few genes
Altered Chromosome Numbers
Aneuploidy – abnormal chromosome number (nondisjunction in meiosis)
Too many chromosome going into one daughter cell
oTrisomy 21 in humans- Down’s Syndrome
Happens more in older women- eggs are getting old too
oTrisomy 18: Edward’s syndrome
oX0: Turner’s syndrome
Gene Expression
Pages 351-364, 373-377 (Concepts 18.1, 18.2, 18.5) ONLY
Fig 18.3
oTryptophan levels inhibit transcription when levels are high
Promoter: region of DNA when RNA polymerase binds to begin transcription
Operator: region on DNA where repressor proteins can bind
Tryptophan bins with repressor= active repressor to block transcription
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