Ch 11, 12, 16 Review

Ch 11, 12, 16 Review - Chapters 11, 12, 16 Review Chapter...

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Chapters 11, 12, 16 Review Chapter 11: Control of Gene Expression The Central Dogma of Biology and Genetics: Transcription Translation DNA RNA Protein Recall that there are several components that play a role in controlling the expression of genes in cells. Remember that all of the cells in our body possess the exact same genes , but that the strict regulation of these genes is what leads to the diverse aspect of each cell type, or their differentiation . A collection of genes that are under coordinated control in bacteria are called an operon . The different components of a gene include: Promoter: Sequence where RNA polymerase binds Operator: Sequence that can be bound by a repressor, preventing transcription Repressor: Protein that can bind to the operator, inhibiting transcription, as a means of genetic regulation Silencer: Specifically, a repressor that prevents transcription from occurring, thus “silencing” its target gene Activator: Protein that can bind to the operator and enhance polymerase binding, and therefore, transcription Enhancer: Region or regions of DNA that can be bound by activator proteins to enhance polymerase activity Transcription factors: Facilitate and enhance polymerase activity Types of operon Control: Inducible Operon: Repressor is initially bound to the operator, and becomes unbound in the presence of the inducer Repressible Operon: Repressor is initially unbound from the operator, and only binds in the presence of a corepressor.
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Gene expression can be regulated by DNA structure: DNA is a double stranded structure composed of nucleic acids. However, this double stranded molecule is organized into higher order structures called nucleosomes . These nucleosomes are consist of the DNA molecule wrapped around histone proteins, and the collections of these nucleosomes are organized into a larger structure called a chromosome . Depending upon which parts of these chromosomes are tightly wound or unwound, different genes can be expressed. This can be seen extensively with the X-chromosome in females. One method of regulation is called X-chromosome inactivation. In this event, one of the two X-chromosomes in a female will become inactive, resulting in the expression of only one set of X-linked genes, those being on the active chromosome. Alternative RNA splicing: Once the message has been transcribed from the gene it exists in the form of mRNA. Shortly thereafter it will be
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Ch 11, 12, 16 Review - Chapters 11, 12, 16 Review Chapter...

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