Cellular Control Flashcards
(21 cards)
What is a mutation?
A random change in the base sequence of the DNA
What are transcription factors?
Proteins that bind to specific DNA sequences to initiate the transcription of structural genes
Define operon.
A cluster of genes controlled by a single promoter
What are the components of an operon?
Regulatory genes - encode proteins that regulate expression of structural genes
A promoter region - site where RNA polymerase binds to initiate transcription
Operator region - sequence where repressor proteins can bind
Structural genes - genes that code for proteins
What is the function of the lac operon in E. coli?
Controls the metabolism of lactose
allows lactose to be used as an energy source when glucose is absent
What is the lacI?
Regulatory gene
Codes for a repressor protein
repressor protein inhibits transcription when lactose is absent
What happens when lactose is present in E. coli?
Lactose binds to repressor protein
Repressor protein changes shape so it cant bind to operator
RNA polymerase can bind to the promoter region
Structural genes can be transcribed
What happens when lactose is absent in E. coli?
The repressor protein binds the the operator
This prevents RNA polymerase from binding to the promoter region
Transcription is inhibited
What are the 3 structural genes of the lac operon?
lacZ:
Beta-galactosidase - breaks down lactose into glucose and galactose
lacY:
Lactose permease - transports lactose into cells
lacA: enzyme for metabolism of lactase
What is the function of cAMP in the lac operon when lactose is present?
cAMP levels increase and binds to cAMP receptor protein (CRP)
CRP-cAMP complex increases transcription of lac operon
lactose is metabolised
What is the function of cAMP in the lac operon when lactose and glucose are present?
Glucose reduces cAMP levels
CRP-cAMP cannot form
lac operon transcription decreases
Structural genes are not transcribed so enzymes are not produced
How is primary mRNA processed to mature mRNA
Adding 5’ cap - stabilizes the mRNA and assists in ribosome binding
Adding a 3’ poly-A tail - stabilizes mRNA and delay degradation
Splicing - Introns are removed and exons are joined together
What are the functions of protein Kinase
Adds phosphate groups to proteins by phosphorylation
Phosphorylation changes proteins tertiary structure and function
This causes different enzymes to be activated
regulated by cAMP
What are the types of mutations?
Substitution - one base replaced for another
Insertion - one or more bases are added
Deletion - one or more bases are removed
Inversion - a sequence of bases are reversed
What is a frameshift mutation?
A mutation caused by insertion or deletion that alters the reading frame of the genetic code
What is an example of a beneficial mutation?
Antibiotic resistance in bacteria
What is the homeobox gene sequence?
Highly conserved DNA sequence that is involved in gene expression and development of an organisms body plan
Similar between organisms
What are hox genes?
A subset of homeobox genes
Contains homeobox sequences essential for correct positioning of body
How does mitosis and apoptosis shape the body
Apoptosis - controlled cell death
Mitosis - cell division
Hox genes control the rate and location of cell division and cell death during development.
How do developmental genes respond to internal stimuli?
Regulatory genes respond to internal stimuli which can cause damage to DNA
When DNA is damaged, regulatory gene stops cell cycle and starts apoptosis
This prevents DNA damage from being replicated into new cell
How do developmental genes respond to external stimuli?
Regulatory genes can respond to external stimuli like change in temp of light intensity
Lack of nutrients may trigger cell division
