chapter 7 outline
chapter 7 outline BIOL 1110
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This 4 page Class Notes was uploaded by Caitrín Hall on Tuesday January 26, 2016. The Class Notes belongs to BIOL 1110 at University of Connecticut taught by Bernard Goffinet in Summer 2015. Since its upload, it has received 15 views. For similar materials see Introduction to Botany in Biology at University of Connecticut.
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Date Created: 01/26/16
DNA and RNA 71 DNA contains two nucleotide strands that wind about each other in a double helix All info that determines characteristics of cell is contained in genome made of DNA Differentiationspecialization rely on process whereby part of genome is expressed in speci c cells lnner and outer environment determine expression DNA is in chromosomes and histones proteins Chromosomes carry genes units of genetic info used for protein synthesis Nucleotides 5carbon sugar deoxyribose phosphate group one of four nitrogenous bases adenine guanine cytosine thymine o Adenine and guanine purines o Thymine and cytosine pyrimidines o Assembled into chain through covalent bonds between phosphate group of one nucleotide and sugar of the next Double helix two strands run in opposite directions one has deoxyribose base while other has phosphate group base held together by hydrogen bonds A amp T form 2 bonds while C amp G form 3 bonds 0 Strands are complementary 72 DNA replicates by separating its two strands and synthesizing two new complementary strands Each single strand can be used as template for another 1 DNA unwinds separate at speci c origins of replication done by helicases 2 Replication forks and bubbles appear because 0 Nucleotides added to 3 end of sequence 0 Each strand is copied in opposite direction 3 Enzyme DNA polymerase reads one strand and assembles complementary Semiconservative half of DNA is original molecule conserved other half is new Proofreading repairs errors in newly formed strand 0 Excision of damaged region by DNA repair nucleases 0 New portion is made by DNA polymerase using other strand as template 0 DNA ligase complete process by sealing remaining break in damaged strand Mutation error is not corrected change in DNA strand is transmitted to next generation can be random mistake damaged DNA before replication evolutionary 73 Genetic information is coded in DNA as groups of three nucleotides o 20 amino acids requires groups of three nucleotides triplets 0 Every triplet is a codon 74 Protein synthesis involves three forms of RNA in the cytoplasm 0 Proteins sequence of amino acids Protein synthesis 0 Step 1 transcription info is copied from DNA to mRNA using the same code of sequences of nucleotides 0 One strand is copied 0 Product mRNA messenger assembly requires enzyme RNA polymerase 0 RNA molecule has determined length and complementary sequence 0 A gene is a sequence of triplets that can be read and translated into AA amino acid sequence 0 lntrons short sequences that do not code for protein must be cut out by process of maturation o Exons code for proteins 0 mRNA formed in nucleus detaches from DNA and moves to cytoplasm to join with ribosomes contain rRNA proteins 0 Step 2 translation tRNA molecules bring amino acids to ribosomes where protein is actually synthesized 0 mRNA molecules read AA brought to ribosomes in correct order AA assembled into protein 0 tRNA transfer transfer amino acids read mRNA Anticodon complement of codon in mRNA that binds to codon Assembled by enzyme aminoacyItRN synthetase 20 amino acids l 60 nucleotide codons l 60 tRNA anticodons 0 Stage 1 initiation tRNA anticodon attaches to start codon of mRNA 0 Stage 2 elongation tRNAs carrying AAs temporarily attach to ribosomes polypeptide chain grows as ribosome moves along mRNA molecule 0 Stage 3 termination Release factors recognize stop codon on mRNA molecule Liberate new synthesized polypeptide and other components in translational system 76 Differences in DNA account for differences among organisms and even among individuals Polymerase Chain Reaction PCR 0 DNA unzips when heated o Read speci c region of genome 2540 times to obtain and align sequences 0 Generates many copies of DNA fragments to be loaded on a gel and separated by electrophoresis to produce a band pattern o Allows DNA contained in small samples to be ampli ed Chapter Wrapup Examine and Discuss SelfTest 1 Translation of an mRNA molecule into a polypeptide begins at the start codon on the mRNA An aminoacyltRNA bearing the amino acid methionine binds to the start codon because it carries the anticodon a TAC and ATG b AUG and TAC c AUG and UAC d UAA and AUU Which of the following molecules is produced by a structural gene a tRNA b mRNA c rRNA d miRNA Given the mRNA sequence GGAUGCUUGGGAGGAGAUGA use the genetic code in Figure 76 to translate the sequence into a short polypeptide Remember that translation begins at start codons and ends at stop codons Consider a fragment of a DNA molecule containing a very short gene genes are usually much longer than this fragment The nucleotide base sequence of this fragment is 39ITI39ACAAAC CAGTCGCTCCCATCCAA Give the resulting nucleotide base or amino acid sequence of the products after the following operations have occurred a replication b transcription into mRNA c Translation into a short polypeptide chain beginning at a start codon Which of the following is considered the most common level of gene regulation in bacteria and archaea a posttranslational b translationalc RNA processing d transcriptional In eukaryotes a premRNA molecule may give rise to multiple types of mRNAs due to the operation of which can remove introns and exons in different patterns a miRNAs b alternative splicingc chromatin remodelingd RNAinduced silencing complex RISC 7 Which of the following best describes the function of a small interfering RNA siRNA in a plant cell a bringing amino acids to a ribosome for assembly into a polypeptide b attacking invasive viral RNAs c inhibiting translation of a complementary plant mRNA d combining with an mRNA molecule to form a ribosome 8 Which of the following groups of organisms would you predict to have the smallest genome size a plants b bacteria c fungi d archaea e both b and d 9 Which of the following DNA ngerprint techniques uses 4 to 6 nucleotide long recognition sequences to cut genomic DNA into fragments for gel electrophoresis a RAPDsb AFLPsc RFLPsd SSRs or microsatellite DNA Applying Concepts Imagine an extraterrestrial lifeform whose DNA uses the same four nitrogenous bases as terrestrial life but must encode for some number of amino acids other than 20 What would be the minimum codon size in bases if a only 14 amino acids must be coded b If 50 amino acids had to be coded c What if 70 amino acids had to be encoded a b c
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