Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Chapter 14: Gene expression & signal transductionGene expression: an introductionEvery plant cell contains a full complement of 20,000-30,000 genes on a set of chromosomesHowever, each cell only expresses a small fraction of genes that relate to the cellular function of that cell type or its stage of developmental What kind of gene would be expressed in all cell types?What kind of a gene would only be expressed in leaves?DNA replicationDNA replication assures that every chromosome and each of the 15,000-50,000 genes that makes up the complete DNA blueprint makes it into every cellTo get a complete set of all chromosomes into every cell the DNA of every chromosome is replicated (copied) prior to mitosis with each of the two dividing cells receiving identical copies of the full set of chromosomes The double helix opens up and the two original strands serve as a template for adding nucleotide monomers that form the new daughter strandsNucleotide base pair rules: G:C and T:AExpressing genes- Step 1: transcriptionTranscription is the making of a copy of a DNA gene into mRNA which is sent to the ribosome to produce a protein. Analogy: sending a scripture to a friendRNA polymerase: enzyme that transcribes mRNA from the DNA templateBase pair rules: G:C A:U DNA  mRNA  proteintranscription translationhttp://www.sinauer.com/cooper/4e/animations0701.htmlExpressing genes- Step 2: translationTranslation is the conversion of the mRNA nucleotide sequence into an aminoacid chain to form a protein 1) mRNA template in sets of three nucleotide combinations called codons 2) tRNA Anticodon- three nucleotide combinations that match the codon Carries the corresponding amino acid 3) Ribosome (Urim and Thumim)Genetic code: three nucleotide codon combinations in mRNA that code for the 20 amino acids found in proteinshttp://www.sinauer.com/cooper/4e/animations0801.htmlYou are a ribosomeAUG AAU AGC UGU CCC CGU GGC CAA UGACoordinating cell function: three steps1) Signal reception: by membrane bound or cytosolic receptor proteins2) Signal transduction: relay of the message from the receptor to the site of the cellular response 3) Activation of cellular response a) transcriptional regulation b) protein modulationSignal receptionReceptors are proteins that perceive hormones or environmental conditions; Receptor may initiate a signaling cascade or act directly as a transcription factor.Signal transductionAn active receptor results in the activation of a signaling pathway with secondary messengers that coordinate all the necessary cellular changesCellular responseTranscriptional regulation 1) Control elements: segments of DNA around gene that determines under what conditions a gene is transcribed 2) Transcription factors: proteins that are produced in response to receptor activation that bind to control elements resulting in the transcription of the complete set of genes for a given responseProtein modulation (fast response): activation of enzymes or ion channelsGene expression: when and how—an example My elm tree last fallWhat processes would the tree need to activate to deal with the early arrival of winter?Chapter 14 Homework questionsExplain how a plant senses and responds to an environmental stimulus. Begin with receptor activation and end with the formation of a response protein.Explain replication, transcription and translation and outline how they contribute to the formation of a protein. What are control elements and transcription factors and what role do they play in determining how plants respond to their