2 Before you go on…Review the answers to the following questions to test your understanding of previous material.DNA performs two unique functions necessary for the perpetuation of life. Briefly describe these two functions.Discuss the significance of specific base pairing in DNA replication (and RNA synthesis).Describe the concept of a gene: where are they, what do they do, and how are they inherited?What are mutations: what causes them, are there different kinds, and can they be repaired?What is the relationship between the informational molecules DNA and RNA?... between these molecules and proteins?List and describe several roles of different proteins in cells. (In other words, why is protein synthesis important?)
3 Learning ObjectivesCompare and contrast the chemical structure and function of DNA and RNA.Discuss the significance of specific base pairing in DNA replication and in RNA synthesis.Name the enzymes important in DNA and RNA synthesis.Differentiate between the processes of transcription and translation.Describe the roles of the 3 different types of RNA in protein synthesis.Messenger RNA contains a start codon and a stop codon. Why is this necessary?Describe what is happening during cell differentiation and animal metamorphosis.Describe the inherited component of cancer development? What happens?
4 Three Classes of RNAs Messenger RNA (mRNA) Ribosomal RNA (rRNA) p. 196Messenger RNA (mRNA)Carries protein-building instructionsRibosomal RNA (rRNA)Major component of ribosomesTransfer RNA (tRNA)Delivers amino acids to enzymes at ribosomes, in the order dictated by mRNA, to build correct polypeptideWhere is RNA made? What two kinds of molecules make up a ribosome? Where do you find ribosomes in a cell?
5 Transcription & DNA Replication Nucleotides added as in DNA replication (specific base pairing)Unlike DNA replication,only small stretch acts as a templateRNA polymerase catalyzes nucleotide additionProduct is a single strand of RNATranscription & DNA ReplicationWhen is DNA replicated normally?Name the enzyme that catalyzes the replication of DNA.p. 196
6 Steps from DNA to Proteins Same two steps produce all proteins:Transcription:DNA is transcribed to form mRNAoccurs in the nucleusmRNA moves into cytoplasm2) Translation:translation occurs at ribosomes (rRNA)mRNA is translated by tRNA to form polypeptide chains, which fold to form functional proteinsHopefully, nothing is lost in translation!
7 DNA to Protein Where might this ribosome be in the cell? What has yet to happen to this polypeptide chain (before it is a functional protein)?Where might this protein be used in the cell?
8 DNA & RNA compared… DNA: RNA: Double stranded Self replicating ACTG basesRNA:Single strandedManufactured from DNAACUG basesMatch base pairs in DNA replication:Match base pairs for RNA synthesis:A -G -C -T -TCGAA -G -C -T -UCGADNA template
9 The “language” of Nucleic Acids DNA codes for amino acids in triplets:TAC CGT AAA CGT …mRNA (messenger RNA): a “copy” of DNA that is read in codons.AUG GCA UUU GCA …tRNA (transfer RNA): ‘interpreter’ of mRNA using “matching” anticodons.AUG GCA UUU GCA …U A CAmino AcidIf the recipe for proteins only had 4 words (ACTG), how would this limit the variety of proteins possible?How many triplets are in a gene that codes for a polypeptide that’s 125 amino acids long?p. 198
11 Protein synthesis translation transcription DNA mRNA U A C tRNA A U G Review mutations… what are the possible effects to the individual? Can these mutations be passed on to offspring?translationtranscriptionDNAmRNAUACtRNAAUGTyrATGProGAp. 200
13 What Happens to the New Polypeptides? Where is the ribosome?Some function in the cytoplasmMany enter the endoplasmic reticulum and move through the endomembrane system where they are modified and shipped to their final destination
14 Animal MetamorphosisWhat has changed inside cells to produce these changes in body form. How is this controlled? What is/are the advantages of metamorphosis?
15 CancerTumors result when the normal mechanisms controlling cell division malfunction.Benign or malignantResult from the accumulation of mutations that transform the cellMutagens and carcinogens increase the risk of cancerTumor suppressing genesProto-oncogenesViruses can insert genetic information into host cells, and move genes to different chromosomesCan we take advantage of this?