Gene Regulation Flashcards
What is gene expression and gene regulation?
The overall process by which genetic information flows from genes to proteins—that is, from genotype to phenotype—is gene expression.
Gene regulation, the turning on and off of genes, can help organisms respond to environmental changes.(proteins can interact with genes to turn them on or off)
What are operons?
In prokaryotes, genes for related enzymes are controlled together in units called operons.
Differentiate between promoter, operatoe and repressor.
Promoter: sequence of DNA where RNA polymerase binds to initiate transcription
Operator: DNA control sequence that acts like a switch (in front of promoter!)
Repressor: protein that can bind to operator to repress transcription by blocking binding of RNA polymerase
Molecules can bind to represors to inactivate them, what are they called and give example.
Inducer. They are called inducer because they facilatate the switching on and off of the operon.
(ex : if lactose is absent in the body, then the repressor binds to the operator and prevents transcription by not allowing RNA polymerase to bind with the promoter.
when lactose is present, it binds to the repressor protein and inactivates it and lets transcription take place.)
What are the two types of operons and give example?
Inducible operons : they are operons that are always turned off, but can be induced by a molecule.
(example : lac operon for lactose)
Repressible operons : are always turned on, but can be repressed by a molecule
(trp operon for tryptophan)
What is positive and negative regulation ,give examples?
Positive regulation involves the binding of an activator to the operator to help RNA polymerase bind better and start transcription (ex: inducible operon)
Negative regulation involves the binding of a repressor to the operator to inhibit RNA polymerase binding and stop transcription (ex: repressible operon)
How does chromosome structure affect transcription?
DNA is made up of small beads called histones, the histones form a string of beads called nucleosome. Histones and nucleosomesmake DNA to be more compact.
For transcription to take place, it involes DNA strands to be separted. If the structure is tight and compact, it becomes harder to seperate therby delaying transcription.
How can the chemical modification of methyl and acetyl groups on amino acids in histone proteins affect transcription?
Methyl groups on amino acids in histone proteins can make chromosomes more compact, leading to reduced transcription
Acetyl groups can open chromatin structure up, promoting transcription
What is epigenetic inheritance and give example?
An inheritance pattern in which a modification to a gene or chromosome alters gene expression in an organism, but the expression is not changed permanently over the course of generations.
(if u have sickle cell anemia and the chromosome that makes your normal haemoglobin is tightly packed then transcription of that is gonnna be much harder so you will have more sickle cells.)
What is an example of DNA packing and epigenetic inheritance?
X chromosome inactivation in the cells of female mammals, where early in embryonic development, one X chromosome is inactivated at random, creating two cell populations.
(example : two chromosomes that carry the allele for orange and black fur respectively, after random inactivation of an X chromosome the kitten will have black and orange fur)
What are transcription factors?
Transcription factors are proteins that promote the binding of RNA polymerase to a gene.
What are enhancers?
Activator proteins need to bind to enhancer sequences to start transcription
Enhancer sequences are usually located far away from the gene they help regulate (can be multiple per gene)
Differentiate between enhancers and operators?
enhancers = before the promoter and far away from gene
operators = after the promoter and close to gene
Explain the regulation of transcription in eukaryotes.
1) To initiate transcription of eukaryotic organisms, activator proteins need to bind to enhancer sequences
2) DNA-bending proteins twist the DNA strands, bringing the activators closer to the promoter.
3) Once bent, activators interact with other transcription factor proteins, making a complex at the promoter,this complex helps RNA polymerase bind and begin transcription
What accounts for the differences in drosophila fruit fly sex?
Alternative RNA splicing. After transcription, alternative RNA splicing may generate two or more types of mRNA from the same transcript.
( splicing doesn’t mean all the exons are put together, different splicing may result in different exons being put together this would result in two more different types of mRNA (bec one doesn’t have the same exons as the other) )
