Gene Expression Regulation 1 Flashcards
What is the purpose of gene expression regulation in bacteria
It allows the cell to save energy by only allowing synthesis of genes that are needed in certain environmental conditions
What is the purpose of gene expression regulation in eukaryotes
It is necessary for cell differentiation
What is the cause of different cell types
It is due to gene expression and not a change in the genomic sequence
What is genetic equivalence
It means that every cell even differentiated ones have the potential (are totipotent) to form an entire organism
What is VDJ recombination
It occurs in B and T lymphocytes at the embryonic period, and receptor selection alters antigen receptor receptivity, and it enhances the recognition of self/non self molecules. It occurs at the DNA level. It is random
What are house keeping genes
They are genes that are present and expressed in all cells, They are important for : structural proteins, RNA polymerase, DNA repair enzymes, ribosomal proteins, enzymes involved in metabolism
Discuss tissue specific genes
Hb is only expressed in reticulocytes, a normal cell expresses 10000 out of 22500 genes, changes at the gene level are subtle. Except for fibrinogen and albumin
How do we measure gene expression (basics)
Denature DNA and then add a probe that is complementarybto the sequence of DNA you are trying to locate, make sure the probe is labelled, then when you find the probe and the DNA you will have found a specific region of the gene that was expressed
How do we find gene expression in RNA
By using gel electrophoresis, when the molecules go to the filter put them in a bag and perform an autoradiology and now you can identify specific sequences, or you could use northern blotting (for which you must have a control to compare to)
What is a DNA microarray
You use a printing technology to place small spots containing probes onto a glass sheet, then label both types of yeast RNA with fluorescent dyes, place equal amounts of the mixture of the 2 rna’s onto the probe plate, and then use the fluorescent light to find out which gene type annealed to which probes
What does transcriptome mean, what does proteome mean
Transcriptome means differences is RNA sequences, and proteome are differences in proteins due to post translational modifications. The sum total of all mRNA expressed from the genes of a molecule
How do we study the proteome
We use a 2D electrophoresis, where we don’t add SDS so the proteins move in the ph strip according to charge density and thus they will have different phs and they will stop at different levels of the ph strip (where they find their isoelectric point), then take this strip horizontally and allow the proteins to pass through the gel electrophoresis by size
What are the different types of gene expression regulation
Transcriptional control, splicing control, RNA transport control, half life control, quality control.
Explain transcriptional regulation, give two examples
Some regions of DNA are called BINDING SITES which are cis-acting elements, they are regulatory proteins that can bind to them, they can activate or inhibit transcription. The lambda repressor, and the lac repressor.
What is helix turn helix motif
It is a region of the DNA BINDING DOMAIN, that has 2 helixes a recognition helix (enters major groove and recognised nucleotide bases) and a N-terminal helix (helps positioning of the recognition helix) Examples: tryptophan repressor, lambda repressor, CAP fragment. They act as dimers and increase the specificity.
What are homeotic gene proteins
They are important for patterning of the human body, they have homeodomains which have a homeobox that is a helix turn helix, and they also have an additional helix
How is regulation done in prokaryotes
By either catabolic pathway (Is also called substrate induction, when the substrate is present then the gene will be expressed) or the anabolic pathway ( is also called end product repression, when the end product is enough then the pathway is stopped)
Detail the characteristics of the lac operon
An operon is a set of genes that are transcribed together into a single mRNA, the lac operon contains the lacZ, lac Y, and lacA genes. It has a promoter which has an operator (a regulatory sequence). The lac repressor can bind to the operator and thus block transcription and synthesis of the 3 genes, if lactose (the effector/inducer) is present then it binds to the repressor such that this complex cannot bind to the operator and and thus transcription takes place and the genes are expressed. Helix turn helix binds as a dimer to a site with 2 identical half sites of the operator and so block the synthesis of the genes
Define the characteristics of the tryptophan operon
This operon codes for 5 enzymes, the tryptophan repressor cannot binds to the operator and thus tryptophan enzymes are synthesized. In the presence of tryptophan then tryptophan binds to the repressor and thus this complex can bind to the operator and stop enzyme synthesis. There are 2 helix turn helix molecules and they bind onto the DNA BINDING sequences
the 2D gel electrophoresis allows you to analyze
the whole proteome
Sodium Dodecyl sulfate
is an anionic detergent applied to proteins to impart a negative charge to linear proteins
the net charge of a protein changes depending on
the ph of the environment
what does the lambda repressor do
shuts off the viral genes that code for the protein components of the new virus particles
lac repressor function is
turn off the production of proteins responsible for lactose metabolism
