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BIOL 3110
Peter Cheung

Sept 15, 2009 Cis-acting Elements and Trans-acting Factors -Refer to fig 2.16 Genes IX -All genes have a control site followed by a coding region. The gene needs to be activated by the control region before proteins can be made (refer also to fig. 2.17 Genes IX) There are 2 copies of each gene (alleles) in the cell and each one has a minute nucleotide difference in order to differentiate the two. -If a mutation occurs at one of the control site that causes the control region to be blocked from the regulatory protein then that allele becomes unviable. -Cis-acting element mutations affect only the DNA molecule to which it is attached. In Trans-acting mutations prevents the expression of both alleles; therefore it is said to be diffusible. -Cis-acting molecules are within the DNA itself whereas Trans-acting molecules are from the regulatory proteins that govern gene activity. -The origin of replication would be the Cis elements whereas the elements needed for replication would be the Trans factors. Physical/Chemical Structure of DNA -Refer to fig. 1.2 Singer & Burk -The lack of the 2’ OH-group makes the DNA molecule more stable than the other possible information storage molecules -The purines are adenine (A) and guanine (G) made of dual cyclic structures, the two pyrimidines are thymine (T) and cytosine (C) made of a single ring. -Base + sugar = nucleoside. Phosphate + base = sugar = nucleotide; the names of the bases also change. -Refer to fig. 1.3 Singer & Burk -the order of the carbons that the phosphates that bind to DNA give it directionality (5’  3’) Double Helix Structure of DNA -What are some of the attractive forces required for the replication of DNA? -Hypothesized that it would require weak forces (ionic and hydrogen bonds, Van der Waals bonds, hydrophobic interactions) not covalent bonds so that the molecule can be separated; a covalent bond would require too much energy. -Hydrophobic forces work by excluding polar molecules as they come together. -On an individual basis these forces are weak but when with the sum of all the weak forces there is sufficient energy for the structure to be held together. -Daughter DNA that is created is always complimentary to the template strand, complimentarity allow
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