PsychDr2B
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Genotype.....Enzyme Activity.....Phenotype
.......G/G.................100.................Normal
.......G/D...................75.................Normal
.......G/LA................120.................Normal
.......G/g....................50.................Normal
.......D/D....................50................Normal
.......D/LA...................95................Normal
......LA/LA.................140................Normal
......LA/g.....................70...............Normal
........g/g....................<5.......Galactosemia
Galactosemia, an inability to metabolize galactose, results from a deficiency of the enzyme
galactose-1-phosphate uridyltransferase. The table above summarizes the genotypes and phenotypes
at this locus. Which of the following alleles show less than normal activity of the enzyme?
A. D and G
B. D and g
C. D and LA
D. D only
E. G and g
F. G and LA
G. G only
H. g and LA
I. g only
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| kalsam
Forum Elite
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Answer B
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| PsychDr2B
Forum Elite
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Excellant again!
The correct answer is B. While the phenotype for D/D is normal, the enzyme activity is decreased. For g/g, the phenotype is affected and the enzyme activity is negligible. If you also look at the enzyme activity levels for heterozygotes such as G/g and G/D, their enzyme activity is diminished, even though their phenotype is normal. LA is an allele with enhanced enzyme activity and the heterozygote LA/D shows almost wild-type enzyme activity. Only the D allele and g allele are consistently associated with decreased enzyme activity.
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| adeelmd
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Posts: 399
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"" For g/g, the phenotype is affected and the enzyme activity is NEGLIGIBLE. If you also look at the enzyme activity levels for heterozygotes such as G/g and G/D, their enzyme activity is DIMINISHED, ""
aren't neglible and diminished synonyms for DECREASED??? I'm totally confused here, as enzyme activity is Decreased/diminished/negligble from normal in all these cases...
g/g could be excluded because it is an abnormal phenotype... but the question should then be "which NORMAL phenotype expresses decreased enzyme activity..." it makes no mention of phenotype, so why are you taking it into account?
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