Presentation on theme: "DNA, RNA, and Protein Synthesis"— Presentation transcript:
1DNA, RNA, and Protein Synthesis Chapter 10DNA, RNA, and Protein Synthesis
2Section 1 Vocabulary Pretest 1. Virulent 2. Transformation 3. BacteriophageViruses that infect bacteriaTransfer of DNA fragments from cell to cellVirus capable of causing disease
3Answer key1. Virulent C 2. Transformation B 3. Bacteriophage A
4Discovery of DNAThree experiments led to the discovery of DNA as the hereditary factor that Mendel described in his experiments with pea plants.Frederick Griffith’s Experiment (1928)—showed that hereditary material can pass from one bacterial cell to another (transformation)Oswald Avery’s Experiment (1940s)—showed that DNA is the hereditary material that transfers information between bacterial cells.Alfred Hershey and Martha Chase’s Experiment (1952)– confirmed that DNA, and not protein, is the hereditary material in all cells.
5EXPERIMENT RESULTS Fig. 16-2 Griffith’s Experiment Mixture of heat-killed S cells and living R cellsEXPERIMENTLiving S cells (control)Living R cells (control)Heat-killed S cells (control)Protective capsuleGriffith concluded that theliving R bacteria had beentransformed into pathogenicS bacteria by an unknown,heritable substance fromthe dead S cells that allowedthe R cells to make capsules.RESULTSFigure 16.2 Can a genetic trait be transferred between different bacterial strains?Mouse diesMouse healthyMouse healthyMouse diesLiving S cells
6Fig. 16-4-1 EXPERIMENT Radioactive protein Phage Bacterial cell DNA Batch 1: radioactive sulfur (35S)DNARadioactive DNAFigure 16.4 Is protein or DNA the genetic material of phage T2?Batch 2: radioactive phosphorus (32P)
7Fig. 16-4-2 EXPERIMENT Empty protein shell Radioactive protein Phage Bacterial cellBatch 1: radioactive sulfur (35S)DNAPhage DNARadioactive DNAFigure 16.4 Is protein or DNA the genetic material of phage T2?Batch 2: radioactive phosphorus (32P)
8Hershey and Chase’s Experiment FigHershey and Chase’s ExperimentSee page 307EXPERIMENTEmpty protein shellRadioactivity (phage protein) in liquidRadioactive proteinPhageBacterial cellBatch 1: radioactive sulfur (35S)DNAPhage DNACentrifugeRadioactive DNAPellet (bacterial cells and contents)Figure 16.4 Is protein or DNA the genetic material of phage T2?Batch 2: radioactive phosphorus (32P)CentrifugeRadioactivity (phage DNA) in pelletPellet
9Section 2 Vocabulary Pretest NucleotideDeoxyriboseNitrogenous basePurinePyrimidineBase-pairing rulesComplementary base pairBase sequenceSugar found in DNAConsists of a sugar, phosphate and nitrogenous baseSingle ring nitrogenous base pairDouble ring nitrogenous base pairRule stating: A always pairs w/ T and C always pairs w/ GOrder of bases on an DNA strandContains nitrogen and carbon atoms and is found on the rungs of a DNA ladderA and T C and G
10Answer Key Nucleotide B Deoxyribose A Nitrogenous base G Purine D Pyrimidine CBase-pairing rules EComplementary base pair HBase sequence F
11DNA Structure By 1950, we knew DNA was the hereditary molecule. How did it work? How did it replicate, store and transmit hereditary information and direct cell function?The answer is found in the unique structure of DNA.
12The structure of DNA was discovered in 1953 by James Watson and Francis Crick.
13Deoxyribonucleic Acid Described as a double helix (twisted ladder).Formed by two long strands of repeating subunits called nucleotides.
14Each nucleotide has three parts: Each nucleotide has three parts:Five-carbon sugar called deoxyribosePhosphate group (phosphorous bonded to 4 oxygens)Nitrogenous base (either adenine, thymine, guanine or cytosine)
15The sides of the ladder are formed by covalently bonding the sugar of one nucleotide to the phosphate of another.SugarPhosphateCovalent bond
16The nitrogenous bases form the rungs of the ladder. There are four types of nitrogen bases:ThymineCytosineAdenineGuanine
17Adenine and Guanine have a double ring of carbon and nitrogen atoms and are called purines. Thymine and Cytosine have a single ring of carbon atoms and nitrogen atoms. They are called pyrimidines
18The bases pair together to form the rungs of the DNA ladder. Hydrogen bonds hold them together.They always pair according to the following base- pairing rules discovered by Erwin Chargaff in 1949:A – TC – GNote: since this pairing guarantees that a purine always pairs with a pyrimidine, the rungs are always the same length
20The base pairs of A/T and C/G are called complementary base pairs. The order of base pairs on a chain of DNA is called its base sequence.Because of its base pairing pattern, one strand of DNA can serve as a template for making a new complementary strand.This is how DNA replicates itself.
21A strand of DNA has the following sequence: C T G G A CWhat is the sequence of the complementary strand?G A C C T G
22Section 3 Vocabulary Pretest DNA replicationHelicaseReplication forkDNA polymeraseSemi-conservative replicationMutationA change in a nucleotide sequence of DNAEnzyme that separates two strands of DNAEnzyme that adds nucleotide bases to copying strands of DNAPoint where two DNA strands separateProcess of copying DNADNA replication that results in one old and one new strand in each copied molecule
23Answer Key DNA replication E Helicase B Replication fork D DNA polymerase CSemi-conservative replication FMutation A
24DNA ReplicationDNA replication is the process by which DNA is copied in a cell before a cell divides by mitosis, meiosis, or binary fission.Steps:Helicases (enzymes) separate the DNA strands by breaking hydrogen bonds between base pairs. This creates an open area of DNA called a replication fork.
25DNA polymerases (more enzymes) add complementary nucleotides to each of the original sides. Notice that synthesis on each strand moves in opposite directions.
26DNA polymerase enzymes fall off and the two new strands completely separate. An enzyme called DNA ligase must fill in gaps created on the strand being copied in the opposite direction.
27The end result is two new identical strands of DNA. This type of replication is called semi-conservative replication because each of the new DNA molecules has kept (or conserved) one of the two (or semi) original DNA strands.
28Speed of Replication DNA adds nucleotides at a rate of 50 per second. However, at this rate it would take 53 days to replicate a large human chromosome.Therefore, replication must begin at several, usually thousands, of different points, or origins, at the same time.
29MutationsAny change in the nucleotide sequence of a DNA molecule is called a mutation.DNA polymerase can check and correct mistakes made during replication.However, mistakes do happen.Mistakes can be spontaneous or caused by environmental factors (radiation, chemicals, etc.)Mutations can be helpful, harmful or harmless.Mistakes made in genes that control cell division can lead to tumors.
30Section 4 Vocabulary Pretest Ribonucleic acidTranscriptionTranslationProtein synthesisRiboseMessenger RNATransfer RNANucleic acid important in protein synthesisSugar found in RNARNA that carries instructions from the nucleus to ribosomesProcess of making an RNA molecule from a DNA templateRNA that assembles an amino acid chainProcess of assembling a protein from a coded RNA messageDNA RNA protein
31Pretest continued RNA polymerase An organism’s entire gene sequence PromoterTermination signalGenetic codeCodonAnticodonGenomeAn organism’s entire gene sequenceSequence of nucleotides at the end of a geneSequence of nucleotides that start transcription3-nucleotide sequence on mRNA that encodes an amino acid3-nucleotide sequence on tRNA that complements a codonSpecifies the amino acid sequence of a proteinEnzyme that catalyzes the formation of RNA
32Answer Key Ribonucleic acid A RNA polymerase N Transcription D Translation FProtein synthesis GRibose BMessenger RNA CTransfer RNA ERNA polymerase NPromoter JTermination signal IGenetic code MCodon KAnticodon LGenome H
33Protein Synthesis (Big Picture) Cells make proteins.The instructions to make a protein are on the DNA in the nucleus.Ribosomes in the cytoplasm make the proteinsCells MUST be able to get the instructions from the DNA inside the nucleus out to the ribosomes.RNA is the messenger !!!
34RNA Structure and Function RNA is different from DNA in 4 waysRNA sugar is riboseUracil replaces thymine as a baseRNA is single strandedRNA is shorter than DNA
35DNA vs. RNA DNA RNA Double Single Deoxyribose Ribose Thymine Uracil Longer Shorter
36Types of RNA Three major types of RNA Messenger RNA (mRNA) —carries instructions for making a protein from a gene in the nucleus to a ribosome in the cytoplasmRibosomal RNA (rRNA) —part of a ribosomeTransfer RNA (tRNA) —transfers amino acids to the ribosome to make a protein.
37rRNA is part of the ribosome. tRNA is folded with many nucleotide bases. However, we emphasize thethree at the bottom.mRNA is made fromDNA in the nucleus. Itcarries the messagefor making a proteinout of the nucleus toa ribosome in thecytoplasm
38Protein SynthesisForming proteins based on information in DNA and carried out by RNA is called protein synthesis.DNA RNA proteinIt involves two processes:TranscriptionTranslation
39TranscriptionTranscription —the genetic code is copied or “transcribed” onto a mRNA in the cell nucleus.Three steps:RNA polymerase (enzyme) binds to a specific site on a DNA molecule called a promoter. This causes DNA to unwind.RNA polymerase uses the base-pairing rules to add the RNA nucleotides that match the DNA code (A/U; C/G)RNA polymerase stops at a termination signal that marks the end of a gene.
41Reading the CodeThe code on the mRNA must next be “read” during the process of translation.This genetic code tells us how a sequence of bases on a DNA molecule (or its RNA messenger) corresponds to a particular amino acid.The code is read three bases at a time. Each 3 base sequence that codes for an amino acid is called a codon.
42Codons in mRNA Notice AUG is the start codon UAA, UAG, and UGA are the stop codons.
43Amino AcidsThe genetic code rules are the same for nearly all living things.The same codons always code for the same amino acids.There are 20 different amino acids.A chain of amino acids makes up a polypeptide.Polypeptides join and twist to make up proteins.It is tRNA and the ribosomes that assemble the proteins during translation.
44Three bases at one end of a tRNA are complementary to a codon on the mRNA. They are called an anticodon.The specific amino acid that the codon codes for is attached to the top of the tRNAA U G G G A C C U
45Translation Translation —the making of a protein Steps: Initiation —ribosomal subunits, mRNA and the tRNA carrying methionine (amino acid of the start signal AUG) bind together.Elongation —the tRNA carrying the amino acid specified by the next codon binds. Peptide bonds form between the amino acids beginning the chain. This continues until a termination signal is reached.Termination —stop codon is reachedDisassembly – the ribosome complex falls apart and the peptide is released.
48The Human GenomeGenome —the complete genetic material contained in an individual.The entire Human Genome consists of 3.2 billion base pairs. We now know the order of these base pairs and have discovered that humans have approximately 30,000 genes.We now need to learn where and when human cells use each of the proteins coded for in the genome.This can help diagnose, treat, and prevent many genetic disorders.