cellular control Flashcards
explain how its possible for a mutation to have no effect on the protein produced from that gene (2 MARKS)
- the degeneracy of the codons
- multiple codons can code for the same gene so doesnt alter the AA sequence
explain how a mutation can alter the protein so that it no longer performs the correct function (2 MARKS)
- frameshift mutation e.g insertion/deletion
- all triplets downstream will be different
describe how a tiger with striped fur may have evolved from a non-striped ancestor In order for lactose to enter the cytoplasm of E. coli a protein is required.
The E. coli living in the digestive system of young mammals are more likely to contain this protein than
E. coli living in the digestive system of old mammals.
Suggest an explanation for this observation.
natural selection
- selection pressure on prey availability
- adapted stripes to hide from prey (camouflage)
- striped tigers reproduce to pass the beneficial genes to offspring
- frequency of the beneficial genes will increase
- over time the entire tiger generation will be striped
regulatory genes
- controlled by transcriptional factors to turn gene off and on during development
- regulatory genes control the pattern
explain how gene expression can be regulated after transcription (3 MARKS)
- premRNA to mature mRNA
- splicing - introns removed and exons joined
- alternative splicing - different combinations of exons can make different versions of mRNA
In order for lactose to enter the cytoplasm of E. coli a protein is required.
The E. coli living in the digestive system of young mammals are more likely to contain this protein than
E. coli living in the digestive system of old mammals.
Suggest an explanation for this observation. (2 MARKS)
- young mammal diet is high in lactose bcs they drink lots of milk
- gene for structural gene is expressed (lac Y for lactose permease)
explain why some regions of DNA is described as non-coding
introns dont code for protein
not present from mRNA
removed via splicing
suggest why non-coding regions of DNA show more variation
not selected against
suggest how allele B inhibits the expression of allele A
B codes for a transcription factor/repressor protein
binds to promoter of A
inhibits enzyme that codes for A
