Abbyies Posted October 27, 2008 Report Share Posted October 27, 2008 Hey can someone please help with this question. it seems basic but i m having difficulties. Test A - #39. The phenotypic ratio from a cross between the genotype: (w is dominant over Ww Bb X wwBb, would be? Thanks for your help. Link to comment Share on other sites More sharing options...
avenir001 Posted October 29, 2008 Report Share Posted October 29, 2008 ask yourself what are the types of gametes that a WwBb genotype could produce? they are: -WB -wb -wB -Wb what types of gametes could a wwBb genotype produce? -wB -wb make a punnett square (or w/e it's called)...u end up with these offspring genotypes: -WwBB, 2WwBb's, Wwbb (4/8=1/2..these have a white phenotype...cuz they all have at least one dominant W allele) -wwBB, 2wwBb's (3/8..these have a black phenotype cuz they lack the dominant W allele but all have the B allele) -wwbb (1/8..brown phenotype...intermediate between white & black) so this question was kinda tricky cuz it turns out W is dominant over B (and over ..but B is dominant over w...and w & b are codominant...these are not immediately obvious from the question, but once u work out the answer and see that 1/2 have to be white (given that W is dominant over , u can right away eliminate the other choices. hope this helps. Link to comment Share on other sites More sharing options...
avenir001 Posted October 31, 2008 Report Share Posted October 31, 2008 ok now i have a question..i was trying some iq pubs chem questions and 2 of the answers indicate that when delta H is positive, the reaction is EXOthermic..i thought it was a typo, but since there's 2 of 'em, i'm wondering if this is the convention to go with for the DAT...anyone know? thank u. Link to comment Share on other sites More sharing options...
mrsparkle Posted November 1, 2008 Report Share Posted November 1, 2008 ok now i have a question..i was trying some iq pubs chem questions and 2 of the answers indicate that when delta H is positive, the reaction is EXOthermic..i thought it was a typo, but since there's 2 of 'em, i'm wondering if this is the convention to go with for the DAT...anyone know? thank u. hey avenir, i was looking at that too... didn't think it was correct either delta H +ve means an endothermic rxn but maybe they mis-typed the question and they meant the reversible rxn. probably a mistake lol im panicking right now... going over all the practice questions again most nervous about bio and RC anyways wish you best of luck tomorrow! Link to comment Share on other sites More sharing options...
avenir001 Posted November 1, 2008 Report Share Posted November 1, 2008 oh thank u..ok then probably a mistake. yes RC is the worst...i'm finding that typically 15 mins isn't enuf for me to answer all ~17 questions...i typically have 3-4 left out of 17 when the time's up...oh wellll *sigh* best wishes to you as well! Link to comment Share on other sites More sharing options...
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