T3: Gene expression, the lac operon and epigenetics Flashcards
What two types of transcription factor are there
Activators - promote RNA polymerase to bind to the promoter region
Repressors - prevent RNA polymerase from binding to the promoter region
Where does RNA polymerase bind to on DNA
Promoter region
Where do TFs bind to
DNA near to the promoter region
What are the parts of an operon
Regulatory gene
Promoter region
Operator region
Structural genes
What do regulatory genes do in operons
Code for a repressor transcription factor
What does the operator region do in an operon
The location where TFs bind
What does the promoter region do in an operon
Area where RNA polymerase binds to start transcription
How do E.coli respire
Aerobically using glucose but can respire lactose in a lack of glucose
What is the normal state of the lac operon
When glucose is being respired, repressor tfs bind to the operator to prevent RNA polymerase from binding so gene lac z, y and A are not expressed
What happens with the lac operon when the E.coli needs to use lactose for respiration
Lactose binds to the lac I repressor gene which changes the shape of the repressor
This allows RNA polymerase to now bind to the promoter region
Genes lac z,y and A can now be transcribed to form mRNA and produce the proteins needed to respire lactose
What is the link between gene combinations and plant flowering
The combination of genes expressed by a plant or parts of a plant determines which sturctures are formed
What is methylation
The addition of methyl groups onto CpG sites
What are CpG sites in DNA
Where a C base is next to a G base on the same strand
What must you call acetylation in your answer
HISTONE MODIFICATION
What does methylation do
Causes DNA to be more tightly wrapped around histones
Makes genes inaccessible - RNA polymerase can’t bind
So genes are not expressed
What does histone modification do in terms of addition of acetyl groups
Causes DNA to be less tightly wound around histones
So genes are accessible for RNA polymerase to bind and for the gene to be transcribed
Name some factors that affect epigentics
Smoking, alcohol diet and exercise
What are oncogenes
Genes that code for proteins involved in the transition between phases in the cell cycle
What are proto-oncogenes
The result of mutations to oncogenes
What is the result of proto-oncogenes
The cell cycle can be continually active
What are tumour suppressor genes
Genes that code for suppressor proteins that stop the cell cycle if there is a problem e.g gene mutation
What can happen if tumour suppressor genes mutate
Cell cycle can be continually active
What is the BRCA1 gene responsible for
Codes for proteins that repair damaged DNA
What happens if someone has 1 faulty BRCA1 allele
If the other becomes damaged, there will be nothing to repair damaged DNA in the body.
