Cellular Control 6.1 Flashcards
Define gene mutation
Gene mutations are a random change to the genetic material
Where can mutations occur?
Mutations can be on either chromosomes or on genes
Compare mutations affecting mitosis and those affecting meiosis
Mutations affecting mitotic division are called somatic mutations and they are not inherited
Mutations affecting meiosis and gamete formation do get inherited
What are 3 things that cause mutations?
Causes of mutations:
- mutagenic chemicals
- replication errors
- high energy ionising radiation
What is a point mutation? Types?
point mutations are where one base is substituted for another
silent, missense, nonsense
Describe a silent mutation and why they are this way?
Silent mutations are a type of point mutation where the change to a base does not result in a different amino acid so nothing changes.This is because the DNA code is degenerate
Describe missense mutation
Missense mutations are point mutations where the base substitution results in a different amino acid being formed so primary structure of protein changes causing the tertiary structure to change meaning the protein is no longer able to do its function
Describe nonsense mutations
Nonsense mutations, a type of point mutation, is where the base substituted codes for a STOP codon creating a truncated protein that will get degraded
What is an indel mutation?
Indel mutations are insertion or deletion of one or more nucleotide causing a frame shift (DNA is non overlapping).
Insertions or deletions in multiples of three result in the addition or deletion of an entire amino acid
What happens when multiples of three nucleotides get inserted or deleted together?
Insertions or deletions of multiples of three result in the addition or deletion of an entire amino acid
Are all mutations harmful?
Not all mutations are harmful some result in variation in the population like eye colour
What is expanding triplet nucleotide repeats?
Expanding nucleotide repeats are where you naturally have a repeating triplet and these increase in number in meiosis. After a certain threshold having a certain number of repeating triplets can cause disease
Discuss rate pof enzyme synthesis
Enzymes catatlysing metabolic reactins in basic functions are synthesised at a constant rate
Enzymes that are only sometimes needed under certain conditions are synthesised are varying rates
What do E.coli usually metabiolise? Wghat might they do instead?
E.coli usuallly metabolises glucose but if glucose is absent then it will metabolise lactose
What does the metabolising of lactose cause?
Lactose metabolism instead of glucose in E.coli induces prodcution of lactose permease (allows lactose entry into the cell) and beta galactocidase (breaks down lactrose into glucose and galactose)
What is an operon?
Operon= genes that may function as a single trnascriptionunit
Desrcibe the structure of lac operon
Lac operon:
- Regulatory gene encodes for the repressor protein lac I
- Control sites: p- promoter region and lac O- operator region
- structural genes: Lac z codes for beta galactocidase and Lac Y which codes for lactose permease
What happens with the lac operon in the absence of lactose?
Absence of lactose:
Lac I binds to operator region blocking RNA polymerase from binding to the promoter region. This therefore prevents transcription of lac z and lac Y so enzymes arent produced
What happens with the lac operon in the absence of glucose?
Absence of glucose:
Lactose binds to lac I, changing its conformational shape so it can no longer bind to the operator region. RNA polymerase can now bind to the promoter, transcribing the genes lac z and lac y so enzymes are made
