6.1.1 Cellular Control Flashcards
What is a mutation?
A mutation is a change in the DNA base sequence
What is a substitution mutation?
One base is replaced by another base, most common type of mutation, most have no effect due to the degeneracy of the genetic code.
What is an insertion or deletion mutation?
Insertion- a new base is added to the base sequence
Deletion- a base is removed from the base sequence
Both lead to a frameshift mutation, altering all colons downstream. Less common but much greater effect on organism
Give examples of mutagens
Mutagens are things that increase the rate of mutations, including uv radiation (ionising radiation) viruses and chemicals like carcinogens
What is a transcription factor?
These proteins can binds to sections of DNA to either increase or decrease rate of transcription as a way to control gene expression.
What is histone modification?
Making DNA more or less accessible by RNA polymerase for transcription. Acetylation and phosphorylation increase rate of transcription as they cause dna to wind loosely due to decreased positive charge. Whereas methylation decreases rate of transcription as it increases the positive charge, causing dna to wind more tightly.
What is an operon?
Operon- cluster of genes controlled by a single promoter for coordinated gene expression.
What is involved in the lac operon?
Regulatory gene- codes for protein which is the transcription factor
Promoter region- binding site for RNA polymerase
Operator region- binding sites for transcription factors
Structural genes- code for proteins
How does the lac operon work?
When lactose is present, lactose binds to the transcription factor, preventing it from binding to the operator. This allows RNA polymerase to bind to the promoter so transcription can occur to produce the proteins. Ensures the lactose enzyme is only produced when lactose is present.
What is cAMP impact on lac operon?
When only lactose is present there is high levels of cAMP (glucose inhibits cAMP) cAMP binds to CAP whi h increases rate of transcription for lactase
What is RNA processing?
Precursor mRNA produced from transcription, must be processed before translation. Introns are removed from pre mrna via RNA splicing and eons are joined together. Alternative splicing allows multiple different combinations of exons to form so multiple different proteins can be formed from one gene.
How does cAMP affect post-translational level of gene expression?
Protein kinases control activity of cell by phosphorylating proteins. This can activate proteins as they are made in an inactive form. Protein kinase activity is regulated by cAMP.
What are homeobox genes?
Groups of regulatory genes. Highly conserved dna sequence used to guide development of the organisms body plan. Act as transcription factors by switching developmental genes on or off.
What are hox genes?
Subset of homeobox genes only found in animals. Needed for the correct positioning of body parts in bodyplan. Control body layers, symmetry ect. Expression colinearity as order of genes is same as the order they are expressed.
What is body morphology?
The use of mitosis and apoptosis. Controlled by hox genes. Important for correct development of body plan.
