shivas mol genetics notes

shivas mol genetics notes - UNIT 6: Molecular Genetics...

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UNIT 6: Molecular Genetics & Ecology Shiva S. DNA STRUCTURE : DNA is made of any nucleotides attached together by phosphodiester bonds A nucleotide is a pentose sugar, a nitrogeneous base, and a phosphate. Deoxyribose sugar 5 carbon sugar with one oxygen and the 5 th carbon sticking out Attached to the 1 st carbon is a nitrogenous base with a glycosyl bond Attached to the 5 th carbon is a phosphate group with an ester bond. Nitrogenous bases held together by hydrogen bonds. The 3 prime end ends with –OH this is where ore nucleotides can attach Nucleotides can only be added at Carbon 3 because there is a OH group so strands can only grow from 5’ to 3’. DNA REPLICATION AND REPAIR 1. Helicase separates the two strands of the double helix to expose the nitrogenous bases. 2. Topoisomerase relieves the tension caused by the unwinding 3. Primase attaches 5 RNA nucleotides to the DNA strand so that the DNA polymerase has something to attach to so it can start copying 4. DNA polymerase attaches to the primer and the DNA strand and starts inserting DNA nucleotide triphosphates that are complementary to those on the DNA strand 5. it only works in the 5' to 3' direction because a new nucleotide can only be attached to the previous base on the #3 carbon's OH group 6. copying continues until it reaches the end of the strand or it meets up with another section that has already been copies 7. the other strand can't be copied all in one piece because it goes the wrong way: it must be copied in short sections that are exposed as the double helix continues to unwind (called Okazaki fragments) and these sections are joined by the ligase enzyme. The DNA polymerase sort of "backs up" along this "discontinuous or lagging strand". 8. DNA Polymerase proofreads for defects and repaires by using nuclease to cut out defect, polymerase replaces it and ligase seals it to place. 9. Methylating enzyme checks by adding methyl groups. PROTEIN SYNTHESIS Transcription: making photocopy (mRNA) from DNA Translation: translating mRNA information into sequence of amino acids. Part A: TRANSCRIPTION 1. All three types of RNA are formed in the same manner by copying DNA sequences. However, rRNA is produced by RNA polymerase I, mRNA by RNA polymerase II, and tRNA is produced by RNA polymerase III. 2. The environmental conditions of the cell stimulate the transcription factors to accumulate and regulatory proteins for a specific gene to bind to the promoter site (TATA box) of that gene, allowing the RNA polymerase to attach to the DNA at the initiation site. 3. The RNA polymerase unwinds the DNA and begins transcribing the sequence of DNA nucleotides into a sequence of RNA nucleotides by adding nucleotide triphosphates. A binds to a T on the DNA, G binds with C, C with a G, and U with an A.
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UNIT 6: Molecular Genetics & Ecology Shiva S. 4. The RNA polymerase stops transcription when it reaches the termination site. The DNA
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shivas mol genetics notes - UNIT 6: Molecular Genetics...

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