7.012 Quiz 1 AnswersA≥87 ~25% of test takersB≥73 ~34% of test takersC≥60 ~24.3% of test takersD≥50 ~10.1% of test takersF≥49 ~6.5% of test takersRegrade requests (with a note attached indicating the problem and part you wantlooked at)Monday 10/04/04QuestionValueScore116220316416515617100MIT Biology Department7.012: Introductory Biology - Fall 2004Instructors: Professor Eric Lander, Professor Robert A. Weinberg, Dr. Claudette Gardel��Question 1 a) Match each boxed chemical interaction in the structures below with the appropriate description. 10 pts _____B_____ peptide bond _______E___ ionic bond ____A_____ van der Waal’s interaction ______D____ phosphodiester bond _____C_____ hydrogen bond CA B DE 2Name________________________________ b) Which one of the following structural features is NOT based on hydrogen bonds? Circle all that apply. 3 pts i) complementary base pairing in DNA ii) protein primary structure iii) protein secondary structure iv) complementary base pairing in RNA c) Your friend tried to remove some writing on a plastic box. He used a napkin dampened with water, which did not work. Then as you advised, he used ethanol (instead of water), and successfully removed the writing. Circle why ethanol was better than water in this case. 3 pts [formula of ethanol: CH3-CH2-OH] i) Ethanol has a greater surface tension, so it extracts the ink molecules better from the plastic. ii) Ethanol can form hydrogen bonds with the ink molecules. iii) One end of ethanol is non-polar. This makes ethanol a better solvent for the ink molecules. iv) Ethanol is more hydrophilic, so it washes off the writing more efficiently. 3Question 2 a) Fill in the percentages. If the value can’t be determined write “ND”. 6 points i) According to Chargaff’s rule, if the DNA content of a cell was composed of 15% A, then C would make up ____35______% , G would make up ___35______%, and T would make up____15%_______ % of the cell’s DNA. ii) If the RNA content of a cell was composed of 15% A, then C would make up ____ND______%, G would make up ____ND_____%, and T would make up____0%_______ % of the cell’s DNA. b) Match the following with all that apply. 6 points A. Lowers the activation energy of a reaction ___ace___ Lactase B. Raises the activation energy of a reaction C. Breaks down milk sugar to galactose and glucose ____ag___ ribozyme D. Lipid E. Protein ___f______ “TheTransforming Principle” F. DNA G. RNA c) Fill in the blanks. 2 pts each i) DNA is synthesized in the _________ direction. Circle one. CN 3’5’ OPNC 5’3’ PO ii) Proteins are synthesized in the _________ direction. Circle onel. . CN 3’5’ OP NC 5’3’ PO d) Which of the following is used to make deoxyribonucleic acid? Circle all that apply.4 points H N OH H 4xxxxxxxxxName________________________________ Question 3 Eukaryotes have proteins called histones that are involved in tightly packing DNA. Below is a schematic of the interaction between a molecule of DNA and the surface of a histone protein. “X” represents an amino acid side chain sticking out from the surface of the protein towards the DNA backbone. x x x xxxxxxxxxxxxxxxFigure by MIT OCW. a) Circle the type(s) of amino acids you would expect to find with side chains in the positions marked “X”? negatively non-polar positively hydrophobiccharged charged 2 pts. b) Circle the strongest interaction between the DNA backbone and the histone protein. hydrogen ionic van der Waals X-linked 2 pts 5Eight histone proteins function as subunits in a multi-protein complex called a nucleosome. Portions of two subunits (HA and HB) interact in the core of the nucleosome. The figure below shows the α− helices where these two proteins interact. Trp Trp Trp Trp TrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrpTrp72 HBHA 72HBHA72HBHAPhe Ile PheIleFigure by MIT OCW. c) Based on the amino acids labeled in the diagram, what interactions keeps HA and HB together? Circle all that apply. 3 pts covalent hydrogen hydrophobic ionic van der Waals d) If tryptophan 72 mutates to become an arginine residue, indicate how the interaction between HA and HB would change. 2 pts. becomes stronger becomes weaker remains the same can not be determined e) Explain your answer in d) in twelve (12) words or less. 3 pts Positive charged does’nt interact with hydrophobic side chain. f) Based on the information given, circle all levels of structure possessed by histones within a nucleosome. 4 pts primary secondary tertiary quaternary quinternary 6--------Name________________________________ STRUCTURES OF AMINO ACIDS at pH 7.0 --O OO O OCO O O CO C C H O H C CH3 H C CH2CH2CH2 N C H C CH2C H C CH2C NH3 O-NH3 NH3 NH2 NH3 NH2 + + NH2+ + + ALANINE ARGININE ASPARAGINE ASPARTIC ACID (ala) (arg) (asn) (asp) --O OO O O O O O CO C C CCO H C CH2 SH H C CH2CH2 O H C CH2CH2C H C H -NH3 NH2 NH3 ++ ++ NH3 NH3 CYSTEINE GLUTAMIC ACID GLUTAMINE GLYCINE (gly)(cys) (glu) (gln) -O O-HO O O OO O C N+HC H C H C C +H C C CH2CH3 H C CH2 C CH3 H C CH2CH2CH2CH2 NH3H C CH2 NH3 C N H NH3 CH3 NH3 CH3 +NH3 ++ + H ISOLEUCINE LEUCINE LYSINE HISTIDINE (ile) (leu) (lys) (his) O O O O-H H OCO -O O CC C H C CH2CH2 S CH3 H C CH2 H HCCH2 H C CH2 OH HNH3 NH3 CH2 CH2 NH3+ + N + +METHIONINE H H H (met) PHENYLALANINE PROLINE SERINE (phe) (pro) (ser) -H HO O --O O HH H O OO O-C C CH3 C H H C CH2 C NH H C H C CH2 OH H C C + H C C CH3 NH3 NH3 NH3 H CH3 NH3 OH ++ H+ HTHREONINE TRYPTOPHAN H VALINE (thr) (trp) TYROSINE (val)(tyr) 7Question 4 Polydactyly is a trait where an individual develops more than five fingers per hand or toes per foot. The pattern of inheritance of polydactyly is shown in the following pedigree. Assume that all individuals marrying in from outside the family do not carry a disease allele. Assume complete penetrance. KEY: normal male normal female affected male affected female 1* 3* 4* 2* ? a) What is the mode of inheritance of this trait? Circle all that apply. 4 pts Autosomal Dominant Mitochondrial Recessive Sex-limited X-linked Y-linked b) What are the genotypes of the numbered individuals? If more than one genotype is possible, write all. Only show the genotype relating to the disease phenotype. Use the letters D, d, XD, Xd, YD, Yd, MD or Md to indicate the genotype corresponding to the polydactyly alleles. 8 pts 1*______Dd_____ 2*_____dd______ 3*____dd_______ 4*_____Dd_____ c) What is
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