Transcription Flashcards
Where does transcription occur?
Nucleus
How many pairs of chromosomes does the human genome hold?
23 pairs (22 + 1 pair of sex chromosomes)
How many protein-coding genomes are there (for humans)?
20,000
What is it called if a gene is expressed always in every cell?
Constitutively expressed genes
How can constitutively expressed genes be used experimentally?
Can be used as comparisons when investigating how stimuli affect gene expression of other genes
What are two examples of constitutively expression genes?
GADPH and beta-actin
What does the expression of specifically expressed genes depend on?
Type of cell and specific stimuli
What types of stimuli might cause changes in gene expression?
Environment, exercise, hormones, diet
How does exercise affect gene expression?
Single bout of exercise significantly changes expression; resistance training causes upregulation of skeletal muscle synthesis; endurance training causes increase in muscle gene expression, particularly genes that are beneficial to aerobic metabolic, e.g. to increased mitochondrial density
What synthesises mRNA, and in what direction?
RNA polymerase II; reads fro 3’ to 5’ to synthesise 5’ to 3’
How many H bonds between between C and G and A and T?
3 between C and G; 2 between A and T
What are promoters and enhances?
Regions of non-coding DNA, which help to regulate and initiate transcription; are control regions that can be acted on by other proteins involved in expression
What are promoters?
Region of DNA that initiates transcription; large number of regions; vary between cell and tissue type; essential to every gene; general transcription factors bind to these regions
What are the three most common promoters?
TATA, CAAT, and GC box
What are transcription factors?
Proteins that alter expression and are involved in activation of promotion of transcription
What are general transcription factors?
Assist RNA polymerase II in initiation; are direct activators; directly interact with DNA
What are co-activator transcription factors?
Bind to RNA polymerase II or other TFs to increase activity; often altering number of co-activators alters rate of gene expression
What causes TFs to activate?
Modification/activation: can be chemical (e.g. phosphorylation) or by direct binding (e.g. hormone binding); changes shape of TF and affects its function. Translocation: to nucleus, as can only do its job unless it’s where the DNA is
What effect does exercise have on TFs?
Endurance training boosts levels of PGC-1-alpha: improves mitochondrial efficiency; increases general biogenesis of mitochondria; specifically activates genes essential to aerobic metabolism
What are enhancers?
Non-coding, non-essential elements of DNA; are located further from site of initiation than promoter; alter level of response when initiation occurs (amount of mRNA produced)
If an enhancer is further in 3’ end, is it upstream or downstream?
Upstream
If an enhancer is further in 5’ end, is it upstream or downstream?
Downstream
What occurs during elongation?
RNA polymerase II complex moves along DNA strand and replicates coding strand to produce mRNA
What occurs during termination?
Occurs when RNA polymerase complex reads a terminator region (poly-A) and complex dissociates from DNA template, release pre-mRNA
Outline the basic process of transcription (post DNA unwinding).
Initiation: general TFs bind to promoter regions and assist RNA polymerase II in initiation; co-activators may alter rate of gene expression. Elongation: RNA polymerase II produces mRNA strand complementary to coding strand. Termination: RNA polymerase II reach poly-A and dissociates from DNA template strand, releasing pre-mRNA for splicing
What does splicing do?
From pre-mRNA, removes introns (complementary mRNA to non-coding DNA which controls rate/way of transcription) and leaves just extrons (complentary mRNA to coding DNA)
How can gene expression be reduced?
Processes which reverse initiation steps (inactivation of TFs, cytoplasmic translocation of factors); directly reduce expression through repressor binding; occurs when stimulus stops or is reduced
How can diet affect gene expression?
Enzymes for digestion upregulated following feeding; hormone response in blood upregulates genes involved in metabolism. Responses depend on: fat vs carb intake; micronutrient/supplement response. Diet can also alter exercise/training response.
What factors of exercise alter effect on gene expression?
Type/modality, intensity, duration
How does exercise affect Type I/Type II prevalence?
Strength athletes see huge increases in Type I and II; endurance athletes see preferential upregulation of Type I
How is end response of gene expression determined?
Stimulus combined with genetic background (nature and nurture)
