PBIO 1210 notes week 5
PBIO 1210 notes week 5 Pbio 1210
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This 3 page Class Notes was uploaded by Maddi Huff on Saturday September 17, 2016. The Class Notes belongs to Pbio 1210 at University of Georgia taught by Momany in Fall 2016. Since its upload, it has received 7 views. For similar materials see Principles of Plant Biology in Plant Biology at University of Georgia.
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Date Created: 09/17/16
Key- vocabulary PBIO 1210- Principles of Plant Biology Week 5 notes 9/13/16 1. DNA a. DNA molecules are comprised of thousands of nucleotides joined together in a chain by their phosphate groups b. Nucleotide: base + deoxyribose sugar + phosphate c. 4 different bases: i. two purines; double ring (adenine and guanine) ii. two pyrimidines; single ring (thymine and cytosine) 2. Double Helix a. DNA: double helix nucleotide chains held together by hydrogen bonds between adenine and thymine (2) and between guanine and cytosine (3) b. twisted ladder with the bases forming the steps and the deoxyribose- phosphate forming the two sides of the ladder c. two strands are not identical but complementary 3. Replication (DNA ->DNA) a. DNA replication: hydrogen bonds between bases broken b. Each single strand has the information to make a new complementary strand i. T in the original strand, an A will be placed opposite it in the new strand ii. Many enzymes and cofactors required. iii. Replication starts at a specific sequence called an origin of replication iv. Helicase enzymes break the hydrogen bonds between bases v. DNA polymerases synthesize the new strand recognizing each base and attaching the correct complementary base 4. Repair a. Errors i. Mistakes sometimes during replication ii. chemicals and UV light b. If the damage is not repaired i. change in DNA (a mutation) may be passed on to other cells. Can be good or bad c. Several enzymes work to repair damage i. DNA polymerases can reverse themselves and go back to repair damage during replication ii. DNA repair nucleases can cut out damaged pieces of DNA and then put in the correct bases iii. DNA ligase connects the repaired section to the main strand 5. Genetic code a. 4 bases in DNA (ACGT) -> 20 amino acids b. code is triplet: a sequence of 3 nucleotides (codon) along the DNA strand calls for particular amino acid Key- vocabulary c. Gene- the linear sequence of nucleotides in DNA that designates all the amino acids in a protein or polypeptide chain 6. RNA a. Messenger RNA (mRNA) b. ribosomal RNA (rRNA) c. Transfer RNA (tRNA) d. Structure i. Nucleotides (base + ribose sugar + phosphate) joined together in a chain by their phosphate groups (similar to DNA) ii. RNA Nucleotides: same bases as found in DNA except uracil replaces thymine iii. RNA molecules are single stranded iv. some parts of RNA molecules may be folded to have sections that are double stranded. 7. Transcription (DNA -> RNA) a. mRNA synthesized by copying one strand of DNA in a complementary fashion b. RNA polymerases attach at a promoter region on DNA c. Open up the DNA double helix d. Add complementary nucleotides and connect to make an RNA e. Carries the genetic instructions to the cytoplasm where protein synthesis occurs f. in eukaryotes, mRNA must be processed before leaving the nucleus g. Introns (sequences that do not code for protein) are cut out h. Exons (code for protein) remain i. To prevent degradation by RNAses in the cytoplasm i. Cap is added at one end ii. Tail of adenine bases is added at the other end 9/15/16 1. Translation (RNA -> protein) a. Genetic code i. Triplet/codon- a sequence of 3 nucleotides along the DNA strand calls for particular amino acid ii. Redundant- more than one codon for most amino acids iii. one start codon- only codon designating the amino acid methionine iv. 3 stop codons b. Ribosomes made of protein and RNA (rRNA) c. Two subunits i. a smaller one with a binding site for mRNA ii. larger one with 3 binding sites for tRNAs d. tRNAs (adaptor) i. Different tRNA for each codon- each is folded in a characteristic way with stems and loops ii. One of the free ends of the tRNA has an attachment site for an amino acid Key- vocabulary iii. Specific enzyme (aminoacyl-tRNA synthetase) recognizes the shape of the tRNA and attaches the correct amino acid iv. In the loop opposite the free ends, 3 bases anticodon v. complementary to the codon for the amino acid that is attached to the tRNA e. Initiation i. Initiator tRNA (methionine) and mRNA attach to the small ribosomal subunit ii. anticodon of the tRNA attaches to the start codon on mRNA iii. The larger ribosomal subunit attaches to the smaller subunit f. Elongation i. tRNAs with amino acids attach to ribosome and to the mRNA codons complementary to the tRNA anticodons ii. A site = Aminoacyl-tRNA receiving site iii. Peptide bonds are formed between the amino acids, and the ribosome moves down the mRNA g. Termination i. At stop codon ii. a cytoplasmic protein binds to the mRNA iii. ribosomal subunits separate iv. mRNA and the protein are released
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