6.1.1 cellular control Flashcards
mutation
random change in base sequence of DNA
what causes a mumtation
mutagen
examples of mutagens
- tar in tobacco smoke
- ionising radiation
2 classes of mutation
- point mutation
- insertion/deletion (indel)
point/substitution mutation
one base pair replaces another
indel mutation
- one or MORE nucleotides are INSERTED or DELETED from a legnth of DNA
- can cause a frameshift
3 types of point mutation
- silent
- missense
- nonsense
silent mutation
triplet code is changed but due to the degenerate nature of code the same amino acid is still produced
- primary secondary tertairy structure of protein all the same
inversion mutation
- eg tac becomes cat
- affects one amino acid
missense mutation
- change in base triplet resulting in a different amino acid produced
nonsense mutation
- base code becomes a STOP triplet
- truncated protein that wont function
frameshift
- caused by INDEL mutation
- when base pairs are inserted/deleted not in threes, due to the code being NON OVERLAPPING
- all the subseqeuent base triplets are altered; all amino acids are altered
expanding triple nucleotide repeat
- repeating triplet sequence repeats even more
why could silent be harmful?
- could code for RNA that regulates the expression of other genes
- could incorrectly regulate this
exon
coding region of DNA
intron
non coding region of DNA
operon
a group of genes that function as a single transcription unit
transcription factors (eukaryote)
- proteins that act to control which genes are turned ON or OFF
simplified, how do TF work
ACTIVATOR:
- bind to promoter region of gene, aiding RNA polyemerase to bind to transcribe the gene
REPRESSOR:
- binds to gene, BLOCKS rna polymerase from binding
operon
a section of DNA containing a cluster of genes which are controlled by a single promoter
3 parts of the operon (link to lac)
- structural genes: (lac z,y,a)
- control elements: (promoter for RNA p to bind and operator where transcription factors can bind)
- regulatory gene: (lac I) codes for transcription factors
ecoli relation to lactose
- e coli normally respires glucose
- if glucose is absent, and LACTOSE present, it induces the production of:
1. lactose permease
2. beta galactosidase
importance of the fact that e coli can only produce these enzymes when glucose absent and lactose present?
- doesnt waste ATP and amino acids on making proteins they dont need
what codes for lactose permease
lac Y
what codes for beta galactosidase
lacZ
beta-galactosidase purpose
breaks glycosidic bonds; hydrolyses lactose to glucose and galactose
what actually induces the enzymes
LACTOSE (but absence of glucose is needed)
what is the purpose of the lac operon
contains the genes that produce the enzymes needed to respire lactose: lactose permease and beta galactosidase
lac operon structure
DRAW
IPOZYA
1. lac I
2. promoter
3. operator
4. lac z
5. lac y
6. lac a
structural genes
genes that code for proteins NOT INVOLVED in DNA regulation
lac z,y,a
are lac z, y , a involved in DNA regulation ?
NO
lac I
- regulatory gene (codes for proteins involved in DNA regulation)
- codes for a REPRESSOR PROTEIN
operator (lac opeoron)
DNA sequence to which repressor protein binds
promoter (lac operon)
DNA sequence to which RNA polymerase binds