Cellular Control Flashcards
Name 3 types of gene mutations
Substitution
Insertion
Deletion
What do insertion and deletion lead to?
Frame shift
Moves the reading frame of bases changing every subsequent codon
Unless nucleotides added/deleted are multiple of 3, then no frame shift but more amino acids are added so protein is still altered
What is substitution?
The changing of a single nucleotide changing the amino acid the codon codes for
However due to degenerative nature of dna, could code for same amino acid
What are the 3 effects of gene mutations and what do they mean?
Beneficial
Rarely a mutation results in a new and useful characteristic in the phenotype
Harmful
Phenotype is altered in a negative way - protein is no longer synthesised or no longer functional
Neutral
The normal phenotype is produced so no effect on phenotype
What are transcription factors?
Proteins in eukaryotic that bind to dna and switch on/off genes by increasing/decreasing the rate of transcription
What is a transcription factor that increases rate of transcription
Activator
What is a repressive protein?
A protein that binds to dna and switches genes off by decreasing the rate of transcription
What is an example of transcription level regulation of gene expression
Lac operon
What is an operon?
A group of genes that are under control of the same regulatory mechanism and are expressed at the same time
What is the lac operon?
A group of 3 structural genes coding for enzymes
Regulatory gene near and coded for repressor protein so transcription is prevented as RNA polymerase cannot bind to promotor
Lactose changes shape of repressor protein so cannot bind
What is post transcriptional level control of gene expression?
Splicing of mRNA
Editing of primary mRNA
What is splicing?
Pre mRNA is modified to mature mRNA so can bind to ribosome
Cuts at specific points to remove the extrons and joining introns together
how is mRNA edited post transcriptionally?
base addition, substitution and deletion resulting in proteins with different functions
how are genes regulated post translationally?
some proteins arent functional when first made so need to be activated. a molecule usually binds to the cell surface membrane causing cyclic AMP to be released inside the cell which axctivates the protein by changing its structure
What is a homeobox gene?
homeotic / regulatory, (gene) ;
contains, 180 bp / homeobox, sequence ;
that codes for homeodomain (on protein) ;
(gene product) binds to DNA ;
initiates transcription / switch genes, on / off ;
control of, development / body plan ;
what are hox genes?
a group of homeobox genes only present in animals, which is responsible for the correct positioning of body parts.
the order in which they appear on the chromosome is the order in which they are expressed
what is apoptosis?
programmed cell death
how to mitosis and apoptosis control the development of body form?
mitosis increases the number of cells leading to growth and apoptosis removes unwanted cells
cells undergoing apoptosis can release chemicals to stimulate mitosis for remodelling
what external stimulis controls apoptosis?
stress, lack of nutrient availability can result in gene expression that prevents mitosis
pathogens can stimulate apoptosis
what internal stimuli control apoptosis?
DNA damage detected during the cell cycle causes expression of a gene that causes the cell cycle to be paused and triggers apoptosis
?what is mitosis and apoptosis regulated by
hox genes
what does RNA polymerase do?
makes mRNA by transcription using a section of DNA o form one strand
what does DNA polymerase do?
used in DNA replication to make 2 DNA strands before cell devision
explain why there is very little change by mutation in homeobox genes?
these genes very important ;
mutation would, have big effects / alter body plan ;
many other genes would be affected / knock-on effects ;
mutation likely to be, lethal / selected against
how does failure of the control mechanism during development lead to webbed fingers
hox genes do not produce transcription factor
so molecules signalling apoptosis are not produced
so apoptosis to separate fingers does not occur
how can gene expression be regulated after transcription?
primary mRNA is modified
removal of introns to produce mature mRNA
alternative splicing to produce different versions of mRNA
protein must be activated by cAMP
binding of cAMP alters the shape of the protein
