Lecture.18.Fall.2013

Genes and regulatory elements regulatory genes are

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

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...
View Full Document

Ask a homework question - tutors are online