Genes and regulatory elements regulatory genes are

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Unformatted text preview: bed into an RNA molecule Genes and Regulatory Elements • Genes • Include: • DNA sequences that encode proteins • Sequences that encode rRNA, tRNA, snRNA, and other types of RNA. Genes and Regulatory Elements • Regulatory genes are genes whose products help determine when or where other genes are transcribed or translated. • Include DNA-binding proteins. transcription factors • Most genes are regulated and only transcribed at certain times and in certain cells. • Some are constitutively (always) transcribed • these are typically required for essential cell functions “housekeeping proteins” essential in all cell, dna polym, catalase, actin for building cytoskeleton—things reqd for life as a cell everything is regulated Genes and Regulatory Elements • Regulatory Elements not genes but sequences • DNA sequences that are not transcribed, but affect the expression of sequences to which they are physically linked. function is cis not trans • Usually recognized by regulatory proteins Levels of Gene Regulation tightly wound=no expression how long does rna live before it is destroyed less energy required early on translated or does it just wait regulate processing of transcripts speed, instantaneous response • Regulation of gene expression takes place at all of these stages. • However, there is an advantage to regulation taking place at early stages. What is it? cellular energy is conserved DNA-binding proteins • Much of gene regulation is accomplished by proteins that bind to DNA sequences and affect their transcription (“transcription factors”). • Not all transcription factors bind directly to DNA • Transcription factor complexes involve many protein-protein interactions DNA-binding proteins • Regulatory proteins generally have discrete functional domains that are bind DNA at specific sequences. • “DNA-binding motifs” can introduce into helix DNA-binding proteins • Some examples of DNA-binding motifs are shown below: • Helix-turn-helix motifs are common in bacterial DNA-binding proteins DNA-binding proteins • Some examples of DNA-binding motifs are shown below: • zinc fingers and leucine zippers are common in eukaryotic DNA-binding proteins. Operons control bacterial transcription • Frequently in bacteria (but not in eukaryotes), genes that have related functions are clustered together under the control of a single promoter. • This grouping of genes and regulatory elements is called an operon. • Genes in an operon are transcribed together into a single mRNA. Operons can be under negative or positive control • Two types of transcriptional control: • Negative control: a regulatory protein is a repressor, binding to DNA...
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