Chapter 15 - Gene Regulation Flashcards
Unit 6 part 2 (also some of ch 13 and 17, sorry)
Why aren’t all genes constantly being transcribed into protein all the time? Use E-Coli needs to answer
Sometimes you gotta wait and see what food I eat so you know what you’re breaking down to produce specific proteins to do that - you don’t need to have it all going at once or you’re wasting energy.
Is the regulation of tryptophan (trp) synthesis positive or negative inhibition?
Negative - more trp = less produced, so level goes closer to set point
How is gene regulation different from feedback regulation?
Fewer steps (no need for the sensor and integrating sensor and potentially effector?)
How is gene regulation similar to feedback inhibition?
Levels are brought closer to the set point
What is the advantage of grouping genes of related function into one transcription unit?
1 on and off switch can control a whole bunch of functionally related genes - you save energy and they’re coordinately controlled
What is an operon? (you can rewrite bc rn it’s KA)
a set of genes that are transcribed under control of a single promoter, resulting in one long mRNA that contains coding sequences for multiple genes + the regulatory DNA sequences that control their expression (including the promoter and binding sites for any repressor or activator proteins).
What is the operator in an operon?
the on/off switch segment where repressor protein binds
What is the promoter in an operon?
the RNA polymerase binding site (with the TATA box)
What are the operon genes?
Genes in the operon (( ͡° ͜ʖ ͡°)) that get transcribed into mRNA that is translated into protein
how does a repressor protein work and where is the gene for the repressor?
It’s a regulatory protein produced by a different gene - it binds to the operator (which is just in front of the genes that would be transcribed), blocking the path of RNA polymerase so the genes can’t be transcribed - no transcription = no protein
What are regulatory genes?
Genes that encode repressor proteins
What is a corepressor?
A molecule (which is prolly a type of ligand) that cooperates with a repressor protein (makes it active/on) to switch an operon off - Example: Tryptophan
What is an inducible operon?
An operon that can be turned on with the removal of a repressor - Default OFF + Catabolic
What is a repressible operon?
An operon that can be turned off with the addition of a repressor - Default ON + Anabolic
Is the Lac operon inducible or repressible?
Incudible
Is the Trp operon inducible or repressible?
Repressible
Summarize the trp operon
. TRP builds up enough to bind to the repressor protein’s allosteric site
. The repressor protein binds to the operator (because its shape has changed due to being activated)
. RNA polymerase is blocked by the repressor protein
. Transcription and therefore protein synthesis stops
What is an inducer?
A small molecule (prolly a type of ligand) that inactivates a repressor by binding to it and changing its shape and triggers the expression of a gene/operon
Example: Allolactose (what you find in a lac operon_)
Summarize the lac operon
. Lactose/Allolactose (rearranged versions of each other) builds up and binds to the active repressor
. This changes the shape so it no longer fits
. RNA pol can now attach and transcribe and genes are expressed
. This breaks down the lactose so it stops binding
. The repressor goes back
Virus vs Bacteria
Bacteria are alive, viruses are not
Viruses are much smaller
Bacteria divide by binary fission, viruses steal (a lot) to divide and survive
Neither have endomembrane systems
What is the lytic cycle?
A virus life cycle where the phage injects its DNA into the host, gets its own proteins synthesized inside the cell, uses that to make new phages, and lysing the cell to let all of that good stuff out (well not good but you get the point)
What is the lysogenic cycle?
A cell cycle where the viral DNA gets injected and merges with the bacteria DNA and divides and gets replicated as a part of the bacteria and only ever expresses itself by random chance when it gets excised from the mother loop and can express itself (but often times the cell WILL NOT POP)
What is Transformation?
Bacteria assimilates DNA as a plasmid from the environmentWh
What is Transduction?
Bacteria assimilates DNA from viruses
What is Conjugation?
Cell to cell transfer of DNA
What is differential gene expression?
The expression of different genes by cells with the same genome
What are the different locations for gene expression regulation?
- Chromatin modification/Dna unpacking
- Transcription
- RNA processing
- Transport to cytoplasm
- Degradation of mRNA
- Translation
- Protein processing
- Degradation of protein
- Transport to cellular function
What is histone acetylation?
Addition of an acetyl group to an amino acid in a histone tail - this promotes transcription by opening up the chromatin structure (too condensed is a bad thing)
What is DNA methylation?
The addition of methyl groups to histones to condense the chromatin and block transcription
What is the result of having a heavily methylated X Chromosome?
It’s inactive and genes aren’t expressed. The methylation gets passed down as cells divide (it can be inherited)
What is epigenetic inheritance?
Inheritance of traits that don’t come from the nucleotide sequence (like having something methylated) (this could explain why 1 twin has schitzophrenia and the other doesn’t)
What are control elements?
Segments of noncoding DNA having particular nucleotide sequences that serve as binding sites for transcription factors (which are proteins)
(this may be a repeat) What are transcription factors?
Regulatory proteins that bind to DNA and affect transcription of specific genes
What are enhancers and where are they in relation to the gene?
Groups of distal (far) control elements that are thousands of nucleotides away (up or down stream but if it makes me pick only one i’d go with up) from the gene (sometimes in an intron)