* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download How an Organism`s Genotype Determines Its Phenotype How an
Proteolysis wikipedia , lookup
Molecular cloning wikipedia , lookup
Endogenous retrovirus wikipedia , lookup
Gene regulatory network wikipedia , lookup
Community fingerprinting wikipedia , lookup
Amino acid synthesis wikipedia , lookup
DNA supercoil wikipedia , lookup
Two-hybrid screening wikipedia , lookup
Metalloprotein wikipedia , lookup
RNA interference wikipedia , lookup
Biochemistry wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Real-time polymerase chain reaction wikipedia , lookup
Non-coding DNA wikipedia , lookup
Promoter (genetics) wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Point mutation wikipedia , lookup
RNA silencing wikipedia , lookup
Polyadenylation wikipedia , lookup
Silencer (genetics) wikipedia , lookup
RNA polymerase II holoenzyme wikipedia , lookup
Eukaryotic transcription wikipedia , lookup
Transcriptional regulation wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Messenger RNA wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Genetic code wikipedia , lookup
Gene expression wikipedia , lookup
How an Organism’s Genotype Determines Its Phenotype 29 How an Organism’s Genotype Determines Its Phenotype • DNA specifies the synthesis of proteins in two stages: • An organism’s genotype is its genetic makeup, the sequence of nucleotide bases in DNA. 1. transcription, the transfer of genetic information from DNA into an RNA molecule and • The phenotype is the organism’s physical traits, which arise from the actions of a wide variety of proteins. 2. translation, the transfer of information from RNA into a protein. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 31 Figure 10.8-1 32 DNA Nucleus Cytoplasm Bioflix Animation: Protein Synthesis © 2013 Pearson Education, Inc. 30 Figure 10.8-2 33 Figure 10.8-3 34 DNA DNA TRANSCRIPTION TRANSCRIPTION Nucleus Nucleus RNA RNA Cytoplasm Cytoplasm TRANSLATION Protein How an Organism’s Genotype Determines Its Phenotype • The major breakthrough in demonstrating the relationship between genes and enzymes came in the 1940s from the work of American geneticists George Beadle and Edward Tatum with the bread mold Neurospora crassa. 35 How an Organism’s Genotype Determines Its Phenotype 36 • Beadle and Tatum – studied strains of mold that were unable to grow on the usual growth medium, – determined that these strains lacked an enzyme in a metabolic pathway that synthesized arginine, – showed that each mutant was defective in a single gene, and – hypothesized that the function of an individual gene is to dictate the production of a specific enzyme. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 10.9 37 How an Organism’s Genotype Determines Its Phenotype 38 • The one gene–one enzyme hypothesis has since been modified. • The function of a gene is to dictate the production of a polypeptide. • A protein may consist of two or more different polypeptides. © 2013 Pearson Education, Inc. From Nucleotides to Amino Acids: An Overview • Genetic information in DNA is – transcribed into RNA, then – translated into polypeptides, – which then fold into proteins. 39 From Nucleotides to Amino Acids: An Overview • What is the language of nucleic acids? – In DNA, it is the linear sequence of nucleotide bases. – A typical gene consists of thousands of nucleotides in a specific sequence. • When a segment of DNA is transcribed, the result is an RNA molecule. • RNA is then translated into a sequence of amino acids in a polypeptide. © 2013 Pearson Education, Inc. 40 © 2013 Pearson Education, Inc. Figure 10.10 41 Gene 1 Figure 10.10a 42 DNA strand Gene 2 TRANSCRIPTION DNA molecule Gene 3 RNA DNA strand TRANSLATION Codon TRANSCRIPTION Polypeptide RNA TRANSLATION Amino acid Codon Polypeptide Amino acid From Nucleotides to Amino Acids: An Overview 43 The Genetic Code • Experiments have verified that the flow of information from gene to protein is based on a triplet code. • The genetic code is the set of rules that convert a nucleotide sequence in RNA to an amino acid sequence. • A codon is a triplet of bases, which codes for one amino acid. • Of the 64 triplets, 44 – 61 code for amino acids and – 3 are stop codons, instructing the ribosomes to end the polypeptide. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 10.11 45 Second base of RNA codon U UUC Phenylalanine UCC (Phe) UUA UCA First base of RNA codon Tyrosine (Tyr) UGC Cysteine (Cys) U C A Stop UCG UAG Stop UGG Tryptophan (Trp) G CUU CCU CAU CUC CCC CAC Leucine (Leu) Leucine (Leu) CUG AUU CCA Proline (Pro) CAA CCG CAG ACU AAU Isoleucine (Ile) ACC AAC ACA Threonine (Thr) AAA Met or start ACG AAG GUU GCU GAU GUC GCC GAC AUC AUA AUG G Serine (Ser) UAC GUA GUG Valine (Val) GCA GCG Alanine (Ala) GAA GAG Histidine (His) Glutamine (Gln) Aspartic acid (Asp) Glutamic acid (Glu) U CGU CGC CGA Arginine (Arg) AGA AGG Serine (Ser) Arginine (Arg) GGA GGG A U C A G • Because diverse organisms share a common genetic code, it is possible to program one species to produce a protein from another species by transplanting DNA. U GGU GGC C G CGG AGU Asparagine AGC (Asn) Lysine (Lys) 46 G UGU UGA Stop CUA A A UAU UAA UUG C C UCU Third base of RNA codon U UUU The Genetic Code Glycine (Gly) C A G © 2013 Pearson Education, Inc. Figure 10.12 47 Transcription: From DNA to RNA • Transcription – makes RNA from a DNA template, – uses a process that resembles the synthesis of a DNA strand during DNA replication, and – substitutes uracil (U) for thymine (T). © 2013 Pearson Education, Inc. 48 Transcription: From DNA to RNA 49 50 • RNA nucleotides are linked by the transcription enzyme RNA polymerase. Animation: Transcription Right click slide / select “Play” © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 51 Figure 10.13 52 RNA polymerase DNA of gene Promoter DNA 1 Initiation RNA Terminator DNA 2 Elongation RNA nucleotides RNA polymerase 3 Termination Growing RNA Newly made RNA Blast Animation: Transcription Select “Play” © 2013 Pearson Education, Inc. Direction of transcription Completed RNA Template strand of DNA (a) A close-up view of transcription RNA polymerase (b) Transcription of a gene Initiation of Transcription 53 • The “start transcribing” signal is a nucleotide sequence called a promoter, which is RNA Elongation 54 • During the second phase of transcription, called elongation, – located in the DNA at the beginning of the gene and – the RNA grows longer and – the RNA strand peels away from its DNA template. – a specific place where RNA polymerase attaches. • The first phase of transcription is initiation, in which – RNA polymerase attaches to the promoter and – RNA synthesis begins. © 2013 Pearson Education, Inc. Termination of Transcription • During the third phase of transcription, called termination, – RNA polymerase reaches a special sequence of bases in the DNA template called a terminator, signaling the end of the gene, © 2013 Pearson Education, Inc. 55 The Processing of Eukaryotic RNA • In the cells of prokaryotes, RNA transcribed from a gene immediately functions as messenger RNA (mRNA), the molecule that is translated into protein. • The eukaryotic cell – polymerase detaches from the RNA and the gene, and – localizes transcription in the nucleus and – the DNA strands rejoin. – modifies, or processes, the RNA transcripts in the nucleus before they move to the cytoplasm for translation by ribosomes. © 2013 Pearson Education, Inc. 56 © 2013 Pearson Education, Inc. 57 The Processing of Eukaryotic RNA • RNA processing includes The Processing of Eukaryotic RNA 58 • RNA splicing is believed to play a significant role in humans – adding a cap and tail consisting of extra nucleotides at the ends of the RNA transcript, – in allowing our approximately 21,000 genes to produce many thousands more polypeptides and – removing introns (noncoding regions of the RNA), and – by varying the exons that are included in the final mRNA. – RNA splicing, joining exons (the parts of the gene that are expressed) together to form messenger RNA (mRNA). © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 10.14 59 Translation: The Players DNA Cap RNA transcript with cap and tail Transcription Addition of cap and tail • Translation is the conversion from the nucleic acid language to the protein language. Introns removed Tail Exons spliced together mRNA Coding sequence Nucleus Cytoplasm © 2013 Pearson Education, Inc. 60 61 Replication Transcription Translation Template DNA DNA RNA Polymer synthesized DNA RNA Polypeptide Monomer nucleotide (deoxyribose) nucleotide (ribose) Amino acid Polymerizing enzyme DNA polymerase RNA polymerase ribosome initiation site origin of replication promoter start site termination site none terminator 1 of 3 stop codons 63 62 Messenger RNA (mRNA) • Translation requires – mRNA, – ATP, – enzymes, – ribosomes, and – transfer RNA (tRNA). © 2013 Pearson Education, Inc. 64 Transfer RNA (tRNA) 65 Figure 10.15 Amino acid attachment site 66 • Transfer RNA (tRNA) – acts as a molecular interpreter, Hydrogen bond – carries amino acids, and – matches amino acids with codons in mRNA using anticodons, a special triplet of bases that is complementary to a codon triplet on mRNA. RNA polynucleotide chain Anticodon tRNA polynucleotide (ribbon model) tRNA (simplified representation) © 2013 Pearson Education, Inc. Ribosomes • Ribosomes are organelles that – coordinate the functions of mRNA and tRNA and 67 Ribosomes • A fully assembled ribosome holds tRNA and mRNA for use in translation. – are made of two subunits. • Each subunit is made up of – proteins and – a considerable amount of another kind of RNA, ribosomal RNA (rRNA). © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 68 Figure 10.16a 69 Figure 10.16b 70 Next amino acid to be added to polypeptide tRNA binding sites P site Growing polypeptide A site Large Ribosome subunit mRNA binding site tRNA mRNA Small subunit (a) A simplified diagram of a ribosome Codons (b) The “players” of translation Figure 10.16 71 Next amino acid to be added to polypeptide tRNA binding sites P site mRNA binding site (a) A simplified diagram of a ribosome • Translation is divided into three phases: 1. initiation, Growing polypeptide A site Translation: The Process 2. elongation, and tRNA Large Ribosome subunit mRNA 3. termination. Small subunit Codons (b) The “players” of translation © 2013 Pearson Education, Inc. 72 Initiation 73 Figure 10.17 74 Cap Start of genetic message • Initiation brings together – mRNA, – the first amino acid with its attached tRNA, and – two subunits of the ribosome. • The mRNA molecule has a cap and tail that help the mRNA bind to the ribosome. End Tail © 2013 Pearson Education, Inc. Initiation 75 76 • Initiation occurs in two steps. 1. An mRNA molecule binds to a small ribosomal subunit, then a special initiator tRNA binds to the start codon, where translation is to begin on the mRNA. 2. A large ribosomal subunit binds to the small one, creating a functional ribosome. Animation: Translation Right click slide / select “Play” © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 10.18 77 Elongation 78 • Elongation occurs in three steps. Met Large ribosomal subunit Initiator tRNA P site A site – Step 1: Codon recognition. The anticodon of an incoming tRNA pairs with the mRNA codon at the A site of the ribosome. mRNA 2 1 Start codon Small ribosomal subunit © 2013 Pearson Education, Inc. Figure 10.19 79 Amino acid Elongation Polypeptide P site Anticodon mRNA A site Codons 1 Codon recognition – The polypeptide leaves the tRNA in the P site and attaches to the amino acid on the tRNA in the A site. – The ribosome catalyzes the bond formation between the two amino acids. ELONGATION Stop codon – Step 2: Peptide bond formation. 2 Peptide bond formation New peptide bond mRNA movement 3 Translocation © 2013 Pearson Education, Inc. 80 Figure 10.19a 81 – The P site tRNA leaves the ribosome. – The tRNA carrying the polypeptide moves from the A to the P site. P site Anticodon mRNA 82 – Step 3: Translocation. Amino acid Polypeptide Elongation A site Codons Peptide bond formation Codon recognition ELONGATION © 2013 Pearson Education, Inc. Figure 10.19b 83 Termination • Elongation continues until New peptide bond – a stop codon reaches the ribosome’s A site, – the completed polypeptide is freed, and – the ribosome splits back into its subunits. mRNA movement Translocation Stop codon ELONGATION © 2013 Pearson Education, Inc. 84 Review: DNA→ → RNA→ → Protein 85 Figure 10.20-1 86 RNA polymerase 1 Transcription • In a cell, genetic information flows from DNA mRNA – DNA to RNA in the nucleus and Nucleus Intron – RNA to protein in the cytoplasm. © 2013 Pearson Education, Inc. Figure 10.20-2 87 RNA polymerase 1 Transcription Nucleus DNA mRNA Figure 10.20-3 88 RNA polymerase 1 Transcription DNA mRNA Intron Intron 2 RNA processing 2 RNA processing Cap Tail Cap Tail Intron Nucleus mRNA Intron mRNA Amino acid tRNA Anticodon ATP Enzyme 3 Amino acid attachment Figure 10.20-4 89 RNA polymerase 1 Transcription Nucleus 90 RNA polymerase 1 Transcription DNA mRNA Figure 10.20-5 DNA mRNA Intron Nucleus Intron 2 RNA processing Anticodon 2 RNA processing Codon Cap Cap Tail Tail Intron mRNA Intron Amino acid mRNA 5 Elongation Amino acid tRNA A tRNA Ribosomal subunits A Ribosomal subunits Anticodon Anticodon Enzyme ATP 3 Amino acid attachment ATP 4 Initiation of translation 3 Amino acid attachment Figure 10.20-6 91 RNA polymerase 1 Transcription Nucleus 4 Initiation of translation Review: DNA→ → RNA→ → Protein • As it is made, a polypeptide DNA mRNA Enzyme – coils and folds and Intron Anticodon 2 RNA processing – assumes a three-dimensional shape, its tertiary structure. Codon Cap Tail Intron mRNA 5 Elongation Polypeptide • Transcription and translation are how genes control the structures and activities of cells. Amino acid tRNA A Ribosomal subunits Stop codon Anticodon ATP Enzyme 3 Amino acid attachment 4 Initiation of translation 6 Termination © 2013 Pearson Education, Inc. 92 Mutations 93 • A mutation is any change in the nucleotide sequence of DNA. Figure 10.21 94 Normal hemoglobin DNA Mutant hemoglobin DNA mRNA mRNA Normal hemoglobin Sickle-cell hemoglobin • Mutations can change the amino acids in a protein. • Mutations can involve – large regions of a chromosome or – just a single nucleotide pair, as occurs in sickle-cell disease. Glu Val © 2013 Pearson Education, Inc. Types of Mutations • Mutations within a gene can be divided into two general categories: 1. nucleotide substitutions (the replacement of one base by another) and 95 Figure 10.22 96 Met Lys Phe Gly mRNA and protein from a normal gene Met Lys Phe Ser Ala Ala (a) Base substitution Deleted 2. nucleotide deletions or insertions (the loss or addition of a nucleotide). • Insertions and deletions can Met Lys Leu Ala (b) Nucleotide deletion – change the reading frame of the genetic message and Inserted – lead to disastrous effects. Met Lys Leu (c) Nucleotide insertion © 2013 Pearson Education, Inc. Trp Arg Figure 10.22a 97 Lys Phe Ser 98 Met Lys Phe Ala Gly mRNA and protein from a normal gene Met Lys Phe Ala Gly mRNA and protein from a normal gene Met Figure 10.22b Deleted Ala Met (a) Base substitution Lys Leu Ala (b) Nucleotide deletion Figure 10.22c 99 Mutations • (1) Wild-type gene – The big red pig ate the red rag. Met Lys Phe Ala Gly mRNA and protein from a normal gene Inserted • (2) Base substitution – The big res pig ate the red rag. • (3) Base addition – The big res dpi gat eth ere dra g. • (4) Base deletion Met Lys Leu (c) Nucleotide insertion Trp Arg – The big re-p iga tet her edr ag. • 3 and 4 are know as frameshift mutations since everything after the mutation is shifted and would likely code for a new sequence of AAs © 2013 Pearson Education, Inc. 100 101 Mutagens VIRUSES AND OTHER NONCELLULAR INFECTIOUS AGENTS 105 • Viruses share some, but not all, characteristics of living organisms. Viruses • Mutations may result from – errors in DNA replication or recombination or – possess genetic material in the form of nucleic acids wrapped in a protein coat, – physical or chemical agents called mutagens. • Mutations – are not cellular, and – are often harmful but – cannot reproduce on their own. – are useful in nature and the laboratory as a source of genetic diversity, which makes evolution by natural selection possible. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 10.24a 106 Protein coat Animal Viruses 121 DNA • Viruses that infect animals cells – are a common cause of disease and – may have RNA or DNA genomes. • Many animal viruses have an outer envelope made of phospholipid membrane, with projecting spikes of protein. © 2013 Pearson Education, Inc. ERROR: stackunderflow OFFENDING COMMAND: ~ STACK: