Cellular control Flashcards
What are gene mutations
Random alteration in the nucleotide sequence of a cell of a living organism
What are point mutations
Changes in an individual gene due to miscopying of one or more nucleotides. They occur at a single point in a sequence
There can be more than one point mutation in a sequence
What are the types of point mutation
Substitution, Insertion and Deletion mutations
What are substitution mutation
The change of one base - resulting in one triplet code
What are insertion mutations
When a new base is inserted into DNA base sequence
Changes the triplet code at the point of mutation - causes a frameshift effect
What are deletion mutations
When a random base is deleted from the nucleotide base sequence
They change triplet code at point of mutation, but also have a frameshift effect
What are the three types of substitution mutations
Silent
Nonsense
Missense
What are silent mutations
Substitution of a base still codes for original amino acid - possible due to the degenerate nature of the genetic code
no effect
What is a nonsense mutation
Premature stop codon is being coded for
Unlikely that final protein would be able to function normally
What is Thalassemia an example of and what are some of its features
Nonsense mutation, sufferers have no synthesis of a beta chain that makes up haemoglobin
What is a missense mutation
A single amino acid is different in final polypeptide, effect can vary depending on role of original amino acid
What is sickle cell disease and example of
A missense mutation causes the RBC to have a distorted shape
What is the Lac Operon
A group of three genes involved in the metabolism of lactose
What does LacI encode for
repressor protein
What does LacO do
it is the operator region of the DNA
What does LacZ encode for
B-galactosidase
What does LacY encode for
permease proteins
What does LacA encode for
B-galactosidase transacetylase - adds an acetyl group to B-galactosidase
How is Repressor protein made
RNA polymerase binds to promotor region of regulatory gene, transcribing the LacI
mRNA is translated by ribosomes to produce a repressor protein that has two binding sites (Lactose, LacO)
What happens when Lactose is absent
Repressor protein binds to LacO, blocking promotor region so that RNA cannot bind to it and the structural genes cannot be transcribed
This means no B-galactosidase is made and no lactose is broken down
What does lactose permease do
transport lactose into the cell
What does B-galactosidase do
Catalyses hydrolysis of lactose into glucose and galactose
What happens when lactose is present
Lactose binds to the binding site on repressor protein, changing the shape so that it cannot bind to LacO
This allows RNA polymerase to bind to LacP so that the structural genes can be transcribe and B-galactosidase is made
Why is lactose called an inducer
It induces the transcription of the enzymes that break it down
