Extra Practice before Quiz 5 KEY

Extra Practice before Quiz 5 KEY - 1

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1. Twin’studies’for’Crohn±s’disease’(CD)’have’shown’50%’concordance’between’monozygotic’twins,’ and’less’than’10%’concordance’between’dizygotic’twins.’What’can’you’conclude’about’the’relative’ effects’of’genetics’and’environment’on’this’disease?’ Choose one. a. Both’genetics’and’environment’contribute’substantially’to’CD. b. CD’is’caused’by’several’genes,’but’not’by’environmental’factors. c. CD’is’caused’by’environment,’but’not’by’genetic’factors. d. CD’has’different’causes’in’monozygotic’twins’than’in’dizygotic’twins. You know that there is an environmental component, because identical (mono-zygotic) twins have less than 100% concordance. At the saeme time, you can tell it is not purely environmental, because of the big difference in concordance between monozygotic and dizygotic twins (who, either either case, share very similar environment). 2. Consider’the’following’data’for’concordance’rates’between’fraternal’and’identical’twins’for’ three’particular’traits. ’ a. Which’of’the’traits’ shows’the’ least’ genetic’influence? ’ Trait C b. Explain’how’the’data’supports’your’choice’in’part’(a).’ Similarity in the concordance values between fraternal twins and identical twins indicates that the trait has a smaller genetic component, because the differences in environment between two people who are twins are not affected much by whether they are identical or fraternal, but the difference in genetic inheritance is: in particular, identical twins have the same genotype at all loci, while fraternal twins have the same genotype at only 50% (of variable loci). Trait’ Percent’ Fraternal Twin’ Concordance’ Percent’ Identical Twin’Concordance ’ A’ 26’ 82’ B’ 8’ 65’ C’ 18’ 21’
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3. Which’of’the’following’experimental’techniques’rely’on’nucleic’acid’hybridization? Choose one or more: a. PCR’ b.
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