Presentation on theme: "KEY CONCEPT DNA structure is the same in all organisms."— Presentation transcript:
1 KEY CONCEPT DNA structure is the same in all organisms.
2 We love D N AMade of nucleotidesSugar, Phosphate and a BaseBonded down one SideAdenine and ThymineMake a Lovely PairCytosine without GuanineWould feel very bareO-O-O deoxy-ribo-nucleic acidR-N-A is ribo-nucleic acid
3 DNA is made up of a long chain of nucleotides. Each nucleotide has three parts.a sugar – deoxyribosephosphate groupa nitrogen-containing basephosphate groupdeoxyribose (sugar)nitrogen-containingbase
4 The nitrogen containing bases - Adenine (A)- Thymine (T)- Cytosine (C)- Guanine (G))* Purines – have 2 rings = Adenine & Guanine* Pyrimidines – have 1 ring = Cytosine & Thymine
5 Watson and Crick determined the three-dimensional structure of DNA 1953Two nucleotide chains that wrap around each other to form a double spiral (double helix)- Temperature liable – a change in T can break apart the DNA strand
6 Rosalind Franklin and Erwin Chargaff. Franklin’s x-ray images suggested that DNA was a double helix of even width.Chargaff’s - Complementary Base Pairing - A=T and C=G.
7 Nucleotides always pair in the same way. Because a pyrimidine (single ring) pairs with a purine (double ring), the helix has a uniform width.A-TC-GCGTA
8 The backbone is connected by covalent bonds. The bases are connected by hydrogen bonds.hydrogen bondcovalent bond
9 8.3 DNA ReplicationKEY CONCEPT DNA replication copies the genetic information of a cell.
10 The rules of base pairing direct replication. 8.3 DNA ReplicationThe rules of base pairing direct replication.A-TG-CDNA is replicated during the S stage of interphase.Happens inside the nucleus
11 DNA serves as a template. 8.3 DNA ReplicationDNA serves as a template.1. Helicase – enzyme that breaks the Hydrogen bonds between the basesReplication Fork – point at which the two chains separate (last bond broken)nucleotideThe DNA molecule unzips in both directions.
12 8.3 DNA ReplicationNew complimentary nucleotide bases pair up on both sides of old DNA templateDNA polymerase (enzyme) forms new Hydrogen bonds between the nucleotidesDNA polymerasenew strandnucleotide
13 8.3 DNA ReplicationTwo new exact copies of DNA are formed, each with an original strand and a newly formed strand.original strandnew strandTwo molecules of DNA
14 Replication is fast and accurate. 8.3 DNA ReplicationReplication is fast and accurate.DNA replication starts at many points in eukaryotic chromosomes.There are many origins of replication in eukaryotic chromosomes.Mutation – change in the nucleotide sequenceDNA polymerases can find and correct errors.Error Rate - one error per 1 billion nucleotides
15 8.4 Transcription RNA differs from DNA in three major ways. RNA – sugar = ribose2. RNA has uracil instead of thymine.U - A3. RNA is a single-stranded structure.
16 8.4 Transcription Three types of RNA. Mesenger RNA (mRNA) – single uncoiled chaincarries genetic information from the DNA in the nucleus to the cytoplasmTransfer RNA (tRNA) – single chain of about 80 nucleotidesfolded into a hairpin shapebinds to specific amino acidsRibosomal RNA (rRNA) – makes up the ribosomes where proteins are made
17 8.4 Transcription Process of copying DNA into mRNA Transcription starts whenRNA polymerase – (enzyme) binds to a Promoter on DNARNA polymerase breaks H-bonds and makes H-bondsOne chain is used as a template(mRNA = transcript)Transcription stops when RNA polymerase reaches a terminatorstart sitenucleotidestranscription complex
18 Transcription vs Replication. Replication copies all the DNA; transcription copies a gene.growing RNA strandsDNAonegene
19 8.5 TranslationKEY CONCEPT Translation converts an mRNA message into a protein.
20 Amino acids are coded by mRNA base sequences. 8.5 TranslationAmino acids are coded by mRNA base sequences.Codon – 3 nucleotides of mRNAAUG = startUAA, UAG, UGA = stopcodon formethionine (Met)leucine (Leu)
21 8.5 TranslationThe genetic code matches each codon to its amino acid
23 8.5 Translation tRNA – transports amino acids to the ribosomes Anticodon – tRNA sequence of 3 nucleotidescomplementary to an mRNA codon.
24 8.5 Translation Translation takes place at the Ribosomes Ribosomes that are attached to the endoplasmic reticulum build proteins for use outside cellRibosomes that are free floating make proteins for use inside cell
25 8.5 TranslationFor translation to begin - Ribosomes attaches to a start codon on mRNA (AUG)Start codon pairs with the anticodon on tRNA (UAC)codes for the first amino acid – methionine – may be removed later if not needed
26 8.5 TranslationAmino acids are bonded together with peptide bonds
27 8.5 TranslationOnce the stop codon is reached, the ribosome releases the protein
28 8.6 Gene Expression and Regulation KEY CONCEPT Gene expression is carefully regulated in both prokaryotic and eukaryotic cells.
29 8.6 Gene Expression and Regulation A promotor is a DNA segment that allows a gene to be transcribed.An operator is a part of DNA that turns a gene “on” or ”off.”The lac operon was one of the first examples of gene regulation to be discovered.has three genes that code for enzymes that break down lactose– milk sugar
30 8.6 Gene Expression and Regulation RNA processingIntrons are nucleotides that are removed from mRNAExons are the nucleotides that are spliced together.Processed mRNA (transcript) goes to ribosome to be made into a protein
31 8.6 Gene Expression and Regulation Coding DNA (genes) make proteinsHumans = 20,000Non-coding DNA (genes) make RNA (transcribed but never translated)Human = 500Human Total = ~ 20,500 genes