AP Biology Gene Regulation

University:
Winston-Salem Forsyth County Schools
Course:
AP Biology
Academic year:

2023
Views:

382

Pages:

3
Author:

laqala0uk

Gene Regulation ● Regulatory sequences are stretches of DNA that interact with regulatory proteins to control transcription ● Activator proteins can turn on/off gene regulation in eukaryotes ● Gene regulation in Eukaryotes includes blocking translation (occurs at the ribosome) ● All cells do not only contain genes for the proteins of that particular tissue (which is why specific ones need to be turned on/off) ● Each Eukaryotic gene has a promoter (DNA sequence where RNA polymerase binds start transcription, proceeding “downstream”) ● RNA processing: ○ Addition of a 5’ cap ○ Addition of a 3’ Poly-A tail (the longer the tail, the more proteins will be produced) ○ Splicing: removing introns and connecting exons ● Eukaryotic DNA is packing using histone proteins ● Epigenetic inheritance: The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence ● Specific transcription factors made in a cell determine which genes are expressed ● In prokaryotes, groups of genes called operons are transcribed in a single mRNA molecule ● Operon: The entire stretch of DNA that includes the operator, the promoter, & the genes that they control ○ A group of functionally related genes that can be coordinately controlled by a single “on-off switch” (the regulatory “switch”) ○ The 2 types of Operons in Prokaryotes: ■ Repressible: A system where the gene is on but it can be turned off (ex. the trp operon) ■ Inducible: A system where the gene is off but it can be turned on (ex. the lac operon) ● Steroid hormones act directly to activate/repress transcription factors ● Protein hormones act via a signal transduction pathway ● Negative regulatory molecules inhibit gene expression by binding to DNA & blocking transcription ○ Ex. DNA methylation (methyl groups are added to certain bases in DNA (usually cytosine) and this restricts RNA polymerase from binding) ○ Individual genes are usually more heavily methylated in cells where they are not expressed ○ The methylation pattern is inherited because it remains through cell division ● Ways Genes Are Regulated In Eukaryotes: ○ Chromatin Modification ■ The histones that are wrapped around the genes can be either loosened or tightened to enhance/decrease transcription ■ Histone acetylation: Makes the DNA more accessible to transcribe → increases transcription ■ DNA methylation: blocks the ability of RNA polymerase to transcribe the genes → decreases transcription ○ Transcription ■ DNA control elements in enhancers bind specific transcription factors ■ Bending of the DNA enables activators to contact proteins at the promoter (initiates transcription) ■ Genes that are in a coordinately controlled group all share a combination of control elements ○ mRNA Degradation ■ Each mRNA has a characteristic life span ○ RNA Processing ■ Alternative RNA splicing ○ Translation ■ Initiation of translation can be controlled via regulation of initiation factors ○ Protein Processing & Degradation ■ Protein processing & degradation are subject to regulation Gene regulation in Prokaryotes VS Eukaryotes Prokaryotes Eukaryotes Operons present No operons present + & - control (ability to induce & repress Primarily + control (ability to induce genes genes from being transcribed) from transcribed) Enhancers rare Enhancers common None Methylation & Acetylation