Genetics Of Living Systems Flashcards
what is a gene mutation
change in the base sequence if DNA which occurs randomly during DNA replication
what makes it most likely occur
when exposed to mutagenic agents, these interfere with DNA replication
what are the 3 results of a gene mutation
- DELETION - one or more base is removed
- INSERTION - one or more base is added
- SUBSTITUTED - one base is replaced for another
what is a frameshift
a frameshift is when the mutation will change the codon and all of the following codons
what type of mutations would cause a frameshift
substitution and insertion
effect of mutations on proteins
- affect the protein structure, different amino acid sequence folding and coiling of secondary structure, different 3d shape
- no effect on the phenotype
- damaging, altered protein decreases the chances of survival,
- beneficial if altered proteins increase chance of survival, antibiotic resistant bacteria
- can occur in promoter regions, might prevent transcription factor binding
silent mutation
doesn’t change the protein being synthesised and occurs in non coding regions of DNA
Nonsense mutation
codon becomes a stop codon instead of coding for an amino acid
Missense mutation
incorrect amino acid is incorporated into the primary structure when a protein is being synthesised.
chromosome mutation changes
- deletion
- duplication
- translocation, a section of one chromosome breaks off and join another non homologous chromosome
- inversion, a section of chromosome breaks off, is reversed and then joins back onto the chromosome
transcription factors
proteins which regulate transcription, they move from the cytoplasm to the nucleus to bind to DNA
Promoter region
dna base sequence before genes where transcription factors bind
what are the different types of transcription factor
- activator proteins stimulate transcription of target genes by helping RNA polymerase to bind the promoter region
- repressor proteins inhibits transcription of target genes by preventing RNA polymerase from binding to the promoter region
different types of transcription factor
- activator proteins stimulate the transcription of target genes by helping RNA polymerase to bind to the promoter region
- repressor proteins inhibit transcription of target genes preventing RNA polymerase from binding to the promoter region
lac operon
an operon is a cluster of genes under the control of promoter
lac operon allows bacteria to metabolise lactose for use in respiration if it is present.
if lactose is absent
- lac repressor binds to the operator
- blocks RNA polymerase from binding to the promoter
- the three structural genes are not transcribed
if lactose is absent
lactose binds to the lac repressor and it changes the shape
the lac repressor cannot bind to the operator
RNA polymerase can bind to the promoter
The three structural genes are not transcribed
post transcriptional mRNA editing
post translational regulation
body plan
homeobox genes
control development of their body sequence of genes which create proteins which regulate the expression of other genes
hox genes
homeobox found in animals, responsible for body development and positioning of body plans
regulates apoptosis and mitosis
mitosis
genetically identical cells
enables the organism to produce more cells and grow
cell differentiate to specialise into different cell types
apoptosis
genetically programmed death
cell shrinks and enzymes digest cell contents into fragments
fragments are engulfed by phagocytes to protect surrounding cells
destroy cells which are no longer needed
destroys cells with damaged dna detected during cell cycle checkpoints
