Presentation on theme: "What does DNA look like? What are the elements that makeup DNA?"— Presentation transcript:
1What does DNA look like? What are the elements that makeup DNA? DNA and RNAWhat does DNA look like?What are the elements that makeup DNA?
2DNA Structure= String of nucleotides (sugar, phosphate, base). Adenine DNA Structure= String of nucleotides (sugar, phosphate, base) *Adenine *Thymine *Guanine *Cytosinepurines - adenine, guaninepyrimidines - cytosine, thymine
3Figure 12–5 DNA Nucleotides PurinesPyrimidinesAdenineGuanineCytosineThyminePhosphate groupDeoxyribose
4Hydrogen Bonds are the “glue” that keeps the two strands together Francis Crick and James Watson (1953)Twisted Double HelixHydrogen Bonds are the “glue” that keeps the two strands togetherEach strand of the helix is a chain of nucleotidesWhat holds the strands together?
5**REMEMBER THIS PHRASE** Always Together….Great CoupleYTOSINEUANIEDENIHYMINEA & T G & C
6Figure 12–7 Structure of DNA NucleotideHydrogen bondsSugar-phosphate backboneKeyAdenine (A)Thymine (T)Cytosine (C)Guanine (G)
7Remember Chromatin?? How is DNA organized in a chromosome? Did You Know?ONE nucleus of ONE human cell = more than 1 meter of DNA!!!Remember Chromatin??What exactly is chromatin?DNA tightly coiled around proteins forming Chromatin which pack together to form thick fibers.
8Prokaryotic Chromosome Structure Section 12-2ChromosomeE. coli bacteriumBases on the chromosome
9Chromosome Structure of Eukaryotes NucleosomeChromosomeDNAdoublehelixCoilsSupercoilsHistones
10How can DNA use its double-stranded structure to its advantage for replication???
11**REMEMBER THIS PHRASE** “Something Old…Something New”
12DNA Replication When does this occur in the cell cycle? Template1) Enzymes un-twist and unzip the molecule (break H bonds between base pairs).2) Each strand serves as a template (something “OLD”)3) Free nitrogen bases form bonds and make complementary strands (Something “NEW”)4) DNA Polymerase bonds the nucleotides and proofreads the molecule
13Figure 12–11 DNA Replication Original strandDNA polymeraseNew strandGrowthDNA polymeraseGrowthReplication forkReplication forkNitrogenous basesNew strandOriginal strand
14DNA vs. RNARNA – also a long chain of nucleotides (5-carbon sugar, phosphate group, nitrogenous base)Differences:RNA sugar = ribose, instead of deoxyriboseRNA – usually single-strandedRNA has uracil to replace thymine (so U binds with A)“Always United & Great Couple”
15RNA is in charge of assembling Amino Acids into Proteins
16From DNA(Gene) to Protein The players:DNA - sequences of nitrogen bases forms the genetic codemRNA - messenger RNA - makes a copy of the DNA in the nucleus and brings it to the rRNAtRNA - transfer RNA - reads the mRNA and brings specific amino acids to the rRNArRNA - ribosomal RNA - location of protein synthesis uses tRNA to make proteins
17Step 1: Transcription = recording the message Occurs in nucleusNew mRNA strand forms from one of DNA strands (creating the message)Let’s Practice…
18Transcription Practice Transcribe the DNA molecule below:ATTATCGCGTAATGCTAATAGCTAATAGCGCATTACGATTATCGTemplatemRNAtranscriptAUUAUCGCGUAAUGCUAAUAGC
19Figure 12–14 Transcription Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)RNA polymeraseDNARNA
20Step 2: Editing of mRNAIntrons are removed – non coding regions of the DNA moleculeExons remain – sequences that will be expressed
21Step 3: Translation = Protein Synthesis Occurs at ribosometRNA reads mRNA which has message from genetic code (DNA)Genetic code is read 3 letters at a time, so each word is 3 bases long
22Every 3 letters is a CODON Each codon codes for a specific amino acid.What does an Amino Acid do again?Helps make proteins!We need codons for Protein Synthesis (Translation)They are like directions to make proteinsEvery set of directions tells you where to START and where to STOPWe too have these, we call them the “start and stop codons”
23Codons to remember…START is always:AUGSTOP is always:UAAUAGUGA
27Translation Practice AUGAUCGCGUAUUGCUACUAG - mRNA Make a polypeptide (chain of amino acids) chain from the mRNA moleculeAUGAUCGCGUAUUGCUACUAG - mRNAmethionine-isoleucine-alanine-tyrosine-cysteine-tyrosine STOP
30Mutations - changes in the DNA sequence Gene mutation- changes in a single genePoint Mutations - substitution of one nucleotide for anotherFrame Shift Mutations - shifting of the genetic code due to insertion or deletion of nucleotideChromosomal mutation changes in the entire chromosome (containing many genes)
32Mutation Analogy THE FAT CAT ATE THE RAT substitution THE FAT CAT ATE THE CAT*The letter “C” was substituted for the “R”insertion THE FAT CAT ATE THE RATTHC EFA TCA TAT ETH ERA T*Because the “C” was added, all other letters shifted down, thereby changing the amino acids that are made.CDeletion THE FAT CAT ATE THE RATTHE FTC ATA TET HER AT*Again, the amino acids will change b/c the “F” was removed
33Mutation Practice ASPARAGINE AUGA CGCGUAUUGCUACUAG - mRNA U What will the new amino acid be if the 5th nucleotide is substituted with an adenine?ASPARAGINEWhat will the new amino acid sequence be if a guanine is inserted between the 9th and 10th nucleotide ?GGUA = VALINE
34When a mutation occurs… If the amino acid sequence is stopped early (a STOP codon is reached) = NonsenseIf the amino acid sequence continues but the wrong amino acids are coded for = Missense
35Putting it all together What is the amino acid sequence that forms from the following DNA molecule? (DNA synthesis)TACTACACCGTATAACAGGGCCTAGCAACTTemplateATGATGTGGCATATTGTCCCGGATCGTTGA