Gwendolyn Quintana 01187235 1 2 3 Choose the answer that best fits the statement Cholesterol is an essential component of biological membranes Although it is much smalle isolate DNA from several different tissues of an animal and find the following molar ratios of moles of each base to moles of phosphate in the samples than the typical phospholipids and glycoplipids in the membrane it is a n molecule having both hydrophilic and hydrophobic regions amphipathic d DNA and RNA are different types of nucleic acid polymer Which of the following is true of DNA but not true of RNA It contains thymine b Match each term related to the structure of nucleic acids A I with one of the descriptions provided A B C D E F G H I base glycosidic bond nucleoside nucleotide phosphoanyhydride bond phosphoester bond ribose phosphodiester bond deoxyribose the linkage between two nucleotides the linkage between the 5 sugar hydroxyl and a phosphate group the nitrogen containing aromatic ring five carbon sugar found in DNA sugar unit linked to a base linkage between the sugar and the base linkages between phosphate groups 4 F 5 H 6 A 7 I 8 C 9 B 10 E 11 D sugar linked to a base and a phosphate 12 G five carbon sugar found in RNA 13 14 15 Your lab director requests that you add new growth medium to the mammalian cell cultures before heading home from the lab on a Friday night Unfortunately you need to make fresh medium because all the pre mixed bottles of medium have been used One of the ingredients you know you need to add is a mix of the essential amino acids those that cannot be made by the cells but are needed in proteins On the shelf of dry chemicals you find the amino acids you need and you mix them into your medium along with all the other necessary nutrients and replace the old medium with your new medium On Sunday you come in to the lab just to check on your cells and find that the cells have not grown You are sure you made the medium correctly but on checking you see that somebody wrote a note on the dry mixture of amino acids you used Note this mixture contains only D amino acids A There are two isoforms of amino acids right handed amino acids D AA and left handed amino acids L AA L amino acids constitute all AA found in proteins during translation in the ribosome therefore essential for general growth and proliferation mitosis etc D amino acids are found in some proteins produced by enzyme posttranslational modifications after translation and translocation to the endoplasmic reticulum they are also important in peptidoglycan cell wall synthesis of bacteria Nonetheless if the mixture did not contain L amino acids proliferation could not occur and thus D AA yield unnecessary What is the meaning of the note and how does it explain the lack of cell growth in your culture 16 17 You are trying to make a synthetic copy of a particular protein but accidentally join the amino acids together in exactly the reverse order One of your classmates says the two proteins must be identical and bets you 20 that your synthetic protein will have exactly the same biological activity as the original You have no hesitation in staking your 20 that it won t What particular feature of a polypeptide chain makes you sure your 20 is safe and that your project will have to be redone As a peptide bond has a distinct chemical polarity a polypeptide chain also has a distinct polarity The reversed protein chains cannot make the same noncovalent interactions during folding and thus will not adopt the same 3 D structure as the original protein The activities of these two proteins will definitely be different since the activity of a protein depends on its 3 D structure It is unlikely that the reverse chain will fold into any well defined and hence functionally useful structure at all because it has not passed the stringent selective pressures imposed during evolution 18 26 Fill in the blanks in the following brief description of the experiment with Streptococcus pneumoniae that identified which biological molecule carries heritable genetic information Some terms may be used more than once Cell free extracts from S strain cells of S pneumoniae were fractionated to purify DNA RNA protein and other cell components Each fraction was then mixed with R strain cells of S pneumoniae Its ability to change these into cells with pathogenic properties resembling the S strain cells was tested by injecting the mixture into mice Only the fraction containing DNA was able to transform the R strain cells to pathogenic or S strain cells that could kill mice 27 The complete set of information found in a given organism s DNA is called its genome d 28 31 The number of cells in an average sized adult human is on the order of 1014 Use this information and the estimate that the length of DNA contained in each cell is 2m to do the following calculations look up the necessary distances and show your working A Over how many miles would the total DNA from the average human stretch 14 miles 14 cells 2miles 2x10 10 2m 2 meters of 2 miles If meters reference below If miles reference above 1 mile 1609 34m 2x1014m 1609 34 m 3 22 x 1017 miles B How many times would the total DNA from the average human wrap around the planet Earth at the Equator Earth s Circumference 24 901 55 miles 24 901 55 miles 2x10 14 miles 8 03x10 9 times 32 36The human genome comprises 23 pairs of chromosomes found in nearly every cell in the body Answer the quantitative questions elow by choosing one of the numbers in the following list 23 69 200 46 92 109 A B C How many centromeres are in each cell 23 What is the main function of the centromere The centromere is a specialized region od the chromosome that plays a critical role in ensuring the correct distribution of duplicated chromosomes to daughter cells during mitosis How many telomeres are in each cell 92 What is their main function Telomere DNA loops back on itself to form a circular structure and associates with a protein complex that protects the ends of chromosomes and plays a role in chromosome replication and maintenance How many replication origins are in each cell Various up to 100 000 present in a single human cell Is their main function A replication of origin is a sequence in which the genome replication process is initiated 37 The figure clearly depicts the nucleolus a nuclear structure that looks like large dark region when stained The other dark speckled regions in this image are the locations of particularly compact