Back to AI Flashcard MakerBiology /Biology IB HL - 7.2 Transcription Part 3
Where do regulatory proteins usually bind, in relation to control elements?
Regulatory proteins typically bind to distal control elements, whereas transcription factors usually bind to proximal elements
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Key Terms
Term
Definition
Where do regulatory proteins usually bind, in relation to control elements?
Regulatory proteins typically bind to distal control elements, whereas transcription factors usually bind to proximal elements
How many control elements do genes have?
Most genes have multiple control elements and hence gene expression is a tightly controlled and coordinated process
What can cause changes in the internal or external environment cause?
Changes in the external or internal environment can result in changes to gene expression patterns
How may the external/internal environment affect gene expression?
Chemical signals within the cell can trigger changes in levels of regulatory proteins or transcription factors in response to stimuli
How do chemical signals affect gene expression?
This allows gene expression to change in response to alterations in intracellular and extracellular conditions
How do hydrangeas change their gene expression in response to environmental changes?
Hydrangeas change colour depending on the pH of the soil (acidic soil = blue flower ; alkaline soil = pink flower)
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| Term | Definition |
|---|---|
Where do regulatory proteins usually bind, in relation to control elements? | Regulatory proteins typically bind to distal control elements, whereas transcription factors usually bind to proximal elements |
How many control elements do genes have? | Most genes have multiple control elements and hence gene expression is a tightly controlled and coordinated process |
What can cause changes in the internal or external environment cause? | Changes in the external or internal environment can result in changes to gene expression patterns |
How may the external/internal environment affect gene expression? | Chemical signals within the cell can trigger changes in levels of regulatory proteins or transcription factors in response to stimuli |
How do chemical signals affect gene expression? | This allows gene expression to change in response to alterations in intracellular and extracellular conditions |
How do hydrangeas change their gene expression in response to environmental changes? | Hydrangeas change colour depending on the pH of the soil (acidic soil = blue flower ; alkaline soil = pink flower) |
How do Himalayan rabbits change their gene expression in response to environmental changes? | The Himalayan rabbit produces a different fur pigment depending on the temperature (>35ºC = white fur ; <30ºC = black fur) |
How do humans change their gene expression in response to environmental changes? | Humans produce different amounts of melanin (skin pigment) depending on light exposure |
How do fish change their gene expression in response to environmental changes? | Certain species of fish, reptile and amphibian can even change gender in response to social cues (e.g. mate availability) |
What do the histone tails determine? | These histone proteins have protruding tails that determine how tightly the DNA is packaged |
How do histone tails typically associate with DNA? | Typically the histone tails have a positive charge and hence associate tightly with the negatively charged DNA |
In what two ways can the histone tails be modified? | Acetylation and methylation |
How does acetylation affect the DNA? | Adding an acetyl group to the tail (acetylation) neutralises the charge, making DNA less tightly coiled and increasing transcription |
How does methylation affect the DNA? | Adding a methyl group to the tail (methylation) maintains the positive charge, making DNA more coiled and reducing transcription |
What is heterochromatin? | When DNA is supercoiled and not accessible for transcription, it exists as condensed heterochromatin |
What is euchromatin? | When the DNA is loosely packed and therefore accessible to the transcription machinery, it exists as euchromatin |
Will all cells have the same amount of eu and heterochromatin? | NO | Different cell types will have varying segments of DNA packaged as heterochromatin and euchromatin |
Is this packaging permanent? | Some segments of DNA may be permanently supercoiled, while other segments may change over the life cycle of the cell |
How can DIRECT methylation of DNA affect gene expression patterns? | Increased methylation of DNA decreases gene expression (by preventing the binding of transcription factors) |
Which genes exhibit more DNA methylation? | Consequently, genes that are not transcribed tend to exhibit more DNA methylation than genes that are actively transcribed |
What is epigenetics? | Epigenetics is the study of changes in phenotype as a result of variations in gene expression levels |
What does epigenetic analysis show? | Epigenetic analysis shows that DNA methylation patterns may change over the course of a lifetime |
What can influence epigenetic changes? | It is influenced by heritability but is not genetically pre-determined (identical twins may have different DNA methylation patterns) |
Will the same cell types have the same methylation? | NO | Different cell types in the same organism may have markedly different DNA methylation patterns |
What environmental factors may influence DNA methylation? | Environmental factors (e.g. diet, pathogen exposure, etc.) may influence the level of DNA methylation within cells |