NAME________________________________TA______________Section #______7.012 Problem Set 2FRIDAY September 17, 2004Answers to this problem set must be inserted into the box outsideProblem sets will NOT be accepted late. Solutions will be posted on the web.Question 1a) What is the molecule shown below?NNNNNH2ONNNNH2NHH N2NONP-OCH3ONHNOOH C2OOOOOO-2OOOO PCHH C2O2OCH-OOO PP-OOOACGT5'3'3'5'PurinesPyrimidinesb) What kind of bonds are indicated by the gray lines?c) Identify the purines and pyrimidines shown.MIT Biology Department7.012: Introductory Biology - Fall 2004Instructors: Professor Eric Lander, Professor Robert A. Weinberg, Dr. Claudette GardelQuestion 2Harry studies plum tree genetics.He had a pure-breeding mutant strain of plum trees that has two unusual characteristics;the mutant tree produces figs instead of plums and there are huge spikes growing out ofthe branches. Harry crossed the mutant with a pure-breeding wild-type plum tree. TheF1 progeny produce figs, but have no spikes.F0:F1:a) For each pair, circle the dominant phenotype.Plums Figs Spikes No spikesb) Harry performed a backcross of an F1 individual with an F0 individual from the mutantstrain. If there are 32 progeny trees from this cross how many trees have each of thefollowing phenotypes?Figs, spikes __________Figs, no spikes _________Plums, spikes __________Plums, no spikes __________Harry performed a test cross of an F1 individual (from the very first cross) with a treeexhibiting both of the phenotypes that you have identified as recessive. He got progenywith the following characteristics.Phenotype# of individuals in F2 generationFigs, spikes897Figs, no spikes97Plums, no spikes903Plums, spikes103Mutant fig tree with spikesWild type plum tree Xfig trees3c) What is the recombination frequency between the “fig” and the “spike” genes? Showyour work._____________Harry had previously identified a mutant plum tree whose branches are magical, and canbe used to make magic wands. The gene that produces this phenotype (the “wand” gene)was previously determined to be 6 map units away from the “spike” gene on onechromosome.d) Based on the above data, there are two possible arrangements for the “fig”, “spike”,and “wand” genes on the chromosome. Draw them below naming the genes in the boxesand indicating between them the distances in map units.Arrangement 1:Arrangement 2:e) What experiment could Harry perform to distinguish between these two possibilities?Question 3The following diagrams show a diploid cell with 2 chromosomes, 1 and 2. The chromosomederived from the mother is denoted "m", and the chromosome derived from the father isdenoted "d".a) The picture below shows the end of mitosis/meiosis I/meosis II. (Circle one.)2mA11d2d1m1d2m2d1mb) The picture below shows the end of mitosis/meiosis I/meosis II. (Circle one.)2d2d1m1d2m1m1m2d1d1d2m2mc) The picture below shows the end of mitosis/meiosis I/meosis II. (Circle one.)1m 1d2m 2d1m 1d1m 1d2m 2d2m 2dd) In which stage of mitosis or meiosis does most of the recombination occur? Explainwhy.5Question 4It is Year 2030, and the first “personned” expedition to Mars is successful. (With theinvention of impulse engines and inertial dampers, this is a trivial accomplishment.) Astunning discovery is made: There is life on Mars! There are round, purring fuzzy,friendly, furry creatures that come in 3 colors: Plush Purple, Ruby Red and Bright Blue.They are dubbed “Martianiti tribbli”, “tribbles” for short (an allusion to an archaic 20thCentury television show).The MIT rocket scientists come to you, a renowned geneticist, Prof. Seven O. Tu to solvethe mystery of tribble coat inheritance.Here are the facts.The scientists can get pure breeding lines of Blue and Red tribbles, but cannot get purebreeding Purple tribbles.Cross 1: Blue x RedF1: All Purple tribblesa) What is the inheritance pattern for coat color? (Circle one)Complementation Dominant Recessive Codominant X-Linkedb) What is the predicted ratio of Blue: Red: Purple tribbles for each of the followingcrosses?i) Cross: Red x PurpleF1: Blues:______________ Reds:______________ Purples: ______________ii) Cross: Purple x PurpleF1: Blues:______________ Reds:_____________ Purples: ______________iii) Cross: Blue x BlueF1: Blues:______________ Reds:_____________ Purples: ______________Question 4 continuedYou find that there is another gene locus (Albino) that controls coat color and is epistaticto the red/purple/blue color locus. When (and only when) a tribble is homozygous “aa” forthis locus, it is pure white, “albino”. (Assume that allele B codes for Blue color and allele bcodes for Red color.)c) Predict the coat color for tribbles with the following genotype:i) Genotype: BB aa ; Phenotype: __________________ii) Genotype: BB AA ; Phenotype: __________________iii) Genotype: Bb Aa ; Phenotype: __________________iv) Genotype: bb aa ; Phenotype: __________________d) Fill in the ratio of progeny classes from the following crosses.CrossPurple ProgenyBlue ProgenyRed ProgenyWhite ProgenyBBAAXBbaa1100BbAaXBbAaBbaaxBBaaBbaaXbbAa7Question 5 A woman with blood type O has a child with blood type O. She claims that a friend ofhers is the child's father. In the ABO system, IA and IB are both dominant to i and arecodominant to each other. ABO genotypes are summarized below and described on page211 of the 1th edition of Freeman.IAIA and IAiAIBIB and IBiBIAIBABiOa) Her friend’s blood type is A. Can he be excluded as the father on this evidence alone?b) Does the fact that the accused man's mother has type A and his father has type ABexclude him from being the parent?c) Does the additional information that his mother's parents are both AB permit him tobe
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