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Unformatted text preview: s i s an o t h er ex am p l e o f h o w c h an g in g o n e • PAO activity → loss of green color: peas become yellow
• PAO gene has two alleles: wt, lof
• wt/wt peas are ___________
• lof/lof peas are ___________
• wt/lof peas are ___________
based on your last answer, which is dominant?
384 THE AMERICAN BIOLOGY TEACHER VOLUME 73, NO. 7, SEPTEMBER 2011 Example 2: Loss of function mutation
tyrosinase gene tyrosinase mRNA tyrosine
(pigment) complete absence of tyrosinase activity
→ complete absence of melanin
→ albinism (one form) Different alleles with different outcomes homozygous for
active enzyme What does a
heterozygous cat look
like? homozygous for
C C *c tyrosinase
tyrosinase General rule for LOF mutations…
Half the amount of wild type gene product is sufficient to give a
wild type phenotype
wild type allele =C
mutant =c exam
Genotype: CC threshold wild type phenotype
albino phenotype Cc c
c 1 wild type copy → enzyme activity above threshold
needed for normal pigmentation, heterozygotes appear unaffected (these are carriers) Temperature-sensitive proteins
Proteins unfold upon heating.
increasing temperature missense...
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This note was uploaded on 10/16/2013 for the course BBIO 360 taught by Professor Marcservetnick during the Fall '12 term at University of Washington.
- Fall '12