Cellular Control Flashcards
What is a somatic mutation?
-mutations associated with mitotic division
-may be associated with development of cancerous tumours
-these mutations are not passed on to offspring
What mutations may be inherited by offspring?
-mutations associated with meiosis and gamete formation
What are the 2 main classes of DNA mutation?
-point/substitution mutation
-insertion or deletion mutation
What is a point/substitution mutation?
List the 3 types of point mutation?
-when one base pair replaces (is substituted for) another
3 types
-silent,missense,nonsense
What is a silent mutation?
-it is a point/substitution mutation involving a change to the base triplet, where the triplet still codes for the same amino acid
-the primary structure of the protein and therefore the secondary and tertiary structure is not altered
What is a missense mutation?
-a change to the base triplet sequence that leads to a change in the amino acid sequence in a protein
-this point /substitution mutation may have a significant effect on the protein produced by altering the primary structure this leads to a change of the tertiary structure of the protein thus altering its shape and preventing it from carrying out its normal function
What is an example of a condition that results from a missense mutation?
-sickle cell anaemia
What is a nonsense mutation ?
-a point mutation that alters a base triplet so that it becomes a stop triplet
-this will severely disrupt the structure of a protein
-the genetic disease muscular dystrophy is the result of a nonsense mutation
What is an insertion or deletion mutation ?
-when one or more nucleotides are inserted or deleted from a length of DNA
-This will cause a frame shift (if not added in multiples of 3) a frame shift will severely disrupt the amino acid sequence. This will alter the primary and therefore the tertiary structure
What do insertions or deletions of a triplet of base pairs result in?
-the addition or loss of an amino acid
What is the preferred respiratory substrate for the bacterium E.coli?
-glucose is the preferred respiratory substrate
-however if glucose is absent and the disaccharide lactose is present ,lactose induces the production of two enzymes (different enzymes are needed to metabolise lactose then glucose)
What two enzymes are needed to metabolise lactose?
-lactose permease- allows lactose to enter the bacterial cell
-β-galoctosidase- hydrolyses lactose to glucose and galactose
What is the operator region on the lac operon?
-lacO
What are the structural genes on the lac operon?
-lacZ- codes for β-galactosidase
-lacY-codes for lactose permease
-lacA-transacetylase
What is the promoter region on the lac operon?
-the promoter region (P) is where the enzyme RNA polymerase binds to begin transcription of the structural genes
What are the control sites on the lac operon?
-the operator region and the promoter region
What is lacI ?
-lacI is a regulatory gene
-it codes for the represor protein that prevents the transcription of the structural genes in the absence of lactose
What happens at the lac operon if lactose is absent?
-the regulatory gene is expressed
-the repressor protein produced binds to the operator
-this prevents RNA polymerase from binding to the promoter region
-the repressor protein therefore prevents the transcription of the structural genes lacZ, lacY and lacA
-TRANSCRIPTION IS PROHIBITED
-the enzymes for the metabolism of lactose are not made
What happens at the lac operon when lactose is present?
-lactose binds to lacI the repressor protein
-this alters the shape of the repressor protein’s DNA binding site, this prevents it from binding to the operator
-RNA polymerase can then bind to the promoter region and the transcription of the structural genes take place
-thus lactose induces the enzymes needed to break it down
What is a transcription factor?
-a protein or short non-coding RNA that can bind to a specific region (promoter region) on a length of DNA to initiate or inhibit transcription of a gene