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Gene regulation

QuestionAnswer
What are the different levels of gene regulation? transcriptional regulation, post-transcriptional regulation, post-translational regulation. Can also regulate the activity of the protein.
define constitutive gene expression: when a gene is transcribed at a relatively constant level under all conditions and cell types.
define regulation gene expression when a gene is transcribed only under certain cellular or environmental conditions, or in certain cell types.
why do we regulate gene expression? organisms need to be able to respond to changes in their environments. In a multicellular organism, cells in a tissue like the gut can have different requirements. These differences require changes in gene expression.
What do we call genes that are needed by all cells e.g. beta-tubulin. Called "essential genes", the expression of which is constitutive.
What is the difference b/w euk and pros when it comes to Activators? In pro - activators bind near the promotor and help recruit RNA pol. In Euk - Activators can bind to enhancer site a LONG way from the promotor, and the DNA can loop over and bring them into contact with the initiation complex.
What effect does Histone Acetylase have on the chromatin? loosens bond b/w histones, making DNA and TATA box more accessible.
What effect does chromatic remodelling complex have on chromatin? creates a condensed chromatin state, making TATA box inaccessible.
What is another factor that determines whether activators or repressors can bind? Ligands - binding to a factor can change its conformation.
Why is the prokaryotic promotor consensus sequence important? shows that this common pattern in -35 and -10 region is important for regulation, and that it's highly conserved and this important for evolution.
WHat do these -35 and -10 regions signify? where sigma factor binds.
define operon group of contiguous genes that are transcribed as a single mRNA molecule, which encodes several different polypeptides
define cistron section of DNA encoding a single polypeptide which fucntions as a hereditary unit. In effect, another word for a gene.
define polycistron mRNA that encodes several different polypeptides - common in bacteria, very rare in eukaryotes.
define operator in prokaryotes, it is a DNA region tht controls transcription of adjacent gene. Binding site for a repressor. Found b/w -10 and -35.
define cis acting element DNA sequences in the vicinit of the structural portion of a gene that are required for gene expression
define trans-acting factors usually proteins, that bind to the cis-acting sequences to control gene expression.
Who discovered the lac operon? François Jacob and Jacques Monod.
How many genes/cistrons does the lac operon encode? 3, which are translated into 3 proteins - ßGalactosidase, permease, and transacetylase.
Under which condition should the lac operon be turned off? just LACTOSE present. The only way it is turned on is if no glucose and no lactose present.
What is TWIST? Twist is an activator that is expressed in presumptive mesodermal cells of early fly embryo. It causes cells to undergo fundamental change in nature (change from stationary epithelial cells to dissociated and migratory cells.
how can TWIST cause cancer? if the human orthologue of TWIST (Twist 1) is turned on, it can activate a whole geentic network that causes benign tumor cells to become migratory and invase i.e. metastasise.
What genes does TWIST activate? Snail and rhomboid. Snail is a repressor of rhomboid.
rhomboid = TWIST – Snail!
define enhancer: A regulatory DNA sequence to which regulatory proteins (trans-acting factors) bind, increasing the rate of transcription of a gene.
How does the LCR act as an enhancer? interacts with regulatory factors present at the promotors of the globin genes. Works by DNA looping.
Given that enhancers can have an influence from a long way away - how is this influence confined to the correct genes? Insulator elements create loops in chromosomes which limit the region an enhancer can affect.
What stops the LCR activating other genes? Insulator sequences - HS5 and 3'HS1
What is a disorder of globin synthesis? Haemoglobinopathies like anaemia and thalassaemia
Describe sickle cell anaemia: Autosomal recessive, low RBCs, reduced life of RBCs, limits oxygen reaching organs, resistance to malaria.
How does sickle cell anaemia arise? From a single base pair mutation in beta-globin gene, causing globins not to fold properly. Glu --> Val.
What's the difference between B0 and B+? B0 - no beta globin produced. B+ diminished beta globin levels.
What does the patient's severity of beta-thalassaemia depend on? what combination of what class of mutations they have,
Created by: lmdavis97
 

 



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