Cellular control (from LOs) Flashcards
Define mutation
Change in the DNA.
Define chromosome mutation
Gain/ loss of whole/part of chromosome.
Define DNA mutation
Change in base sequence.
Define mutagens
Increases chance of a mutation occuring
Define somatic mutation
Mutation in cell which is not a gamete/ cannot be passed on to offspring.
Define allele
Version of a gene.
List some examples of mutagens
UV, tar, radiation
State when DNA mutations may occur
When DNA replicates
Explain the differences between a somatic mutation and a mutation that occurs during meiosis
Somatic mutation not passed onto offspring, mutation occurs during meiosis = gamete has new allele = mutation passed onto offspring.
What are the 3 types of mutation?
Point, insertion and deletion.
What happens in a point mutation?
1 base replaces another
What happens in an insertion mutation?
1 extra nucleotide added
What happens in a deletion mutation?
1 nucleotide removed.
Explain what is meant by the term “frame shift”
All codons after the mutation are changed
State and explain which type of DNA mutation is likely to have the greatest effect on the protein produced.
Insertion/deletion
cause a frame shift
all codons after the mutation changed
so secondary and tertiary structures changed, so shape changed = not function or function differently.
Explain why a substitution mutation may not affect the protein produced
Code is degenerate so new codon may still code for the same amino acid.
Define gene expression
Whether a gene is switched on or off (i.e. whether a gene is used to produce a protein or not).
Define operon
Length of DNA which is made of structural genes and control sites.
Define enzyme induction
Switching on the gene to make the enzyme when needed.
Define inducer
Molecule which causes the production of the protein/ switches the gene on.
Define repressor protein
Molecule which switches the gene off.
Define transcription level
This means controling if transcription happens or not.
Define transcription factor
Molecule (usually a protein or group of proteins) which binds to the operator region before a gene, making it possible for the RNA polymerase to bind so transcription can occur.
Explain why there are large numbers of some proteins but only small numbers of other proteins in a cell
Genes switched on/ off at different levels.
Name the 2 enzymes required to metabolise lactose
Lactose permease and beta- galactosidase
What is the function of lactose permease?
Transports lactose into the cell.
What is the function of beta-galactosidase?
Hydrolyses lactose/ converts to glucose and galactose.
Explain why, when supplied with lactose, bacteria cannot initially respire it
Don’t have these 2 enzymes
State the function of each part of the lac operon
P and O are control sites, RNA polymerase needs to bind to P The repressor binds to O, preventing RNA polymerase binding. Z codes for B galactosidase Y codes for lactose permease
Name the gene which is not part of the operon but whose product helps with the functioning of the operon.
Regulatory gene
Describe how the lac operon works when there is no lactose
B galactosidase and lactose permease genes are switched off.
Regulator genes expressed
Repressor protein synthesised
Repressor protein binds to operator region
Repressor protein covers part of promotor region
RNA polymerase cannot bind to promoter
No transcription
No B galactosidase and lactose permease
Describe how the lac operon works when lactose is present
B galactosidase and lactose permease genes are switched on.
Lactose is the inducer
Binds to complementary site on repressor protein
Repressor protein changes shape
Repressor protein cannot bind to operator region
RNA polymerase can bind to promoter region
B galactosidase and lactose permease genes are transcribed
B galactosidase and lactose permease genes are produced.
Define post transcription
Events that occur after transcription (after mRNA has been made)
Define post translation
Events that occur after translation (after the protein has been made)
Define intron
Non-coding DNA (sequence of bases which do not code for amino acids in the protein).
Define primary mRNA
mRNA which is produced during transcription.
Define mature mRNA
mRNA that is used at the ribosome to make the protein.
Outline how primary mRNA is converted to mature mRNA
Introns are removed, by the enzymes
Describe how proteins are activated post translation
By cyclic AMP, this changes their tertiary structure, to make shape of protein complementary to shape of molecule it needs to bind to.
Define mitosis
Cell division which produces clones
Define differentiation
Process cells go through to become specialised
Define homeobox gene
Gene which controls development of organism
Define polarity
Difference in charge.
Define hox cluster
Several homeobox genes located together
What is the anterior side of an organism?
Head
What is the posterior side of an organism?
Tail
What is the dorsal side of an organism?
Top
What is the ventral side of an organism?
Bottom
What are 3 types of homeobox genes?
Maternal effect gene, homeobox gene and segmentation gene.
What is the function of the maternal effect gene?
Determine polarity of the embryo
What is the function of the homeobox gene?
Determine identity of each segment
What is the function of the segmentation gene?
Determine polarity of each segment
Describe the 2 types of homeotic selector genes
Thorax and abdomen selector genes.
Describe the effect a mutation in a homeobox selector gene could have.
Body part in the wrong position.
State what type of protein homeobox genes code for
Transcription factors
Explain how homeobox genes control development
Each homeobox gene codes for one transcription factor, this then switches on/off genes to make that segment.
Describe the relationship between order of activation and location and expression of homeobox genes
Activated in the order they are expressed along the organism.
