Cellular control
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what’s a mutation
a random change to the genetic material
define mutagenic
factor that increases chance of mutation
what’s a gene mutation
change to DNA
are somatic mutations passed on to offspring
no, but those in meiosis are
what are the 2 ,main classes of DNA mutation
• point mutation: one base is substituted for another • indel mutation: one or more nucleotides are inserted or deleted from a length of DNA, may cause a frameshift
what are the three types of point mutations
• silent • missense • nonsense
what are silent mutations
• change in triplet base, where that triplet still codes for the same aa so protein structure isn’t altered • due to degeneracy of the genetic code
what are missense mutations
• change to the base triplet sequence that leads to a change in aa sequence in protein • alteration to 1* structure leads to change 3*, altering shape + preventing usual function
what are nonsense mutations
• point mutations may alter a base triplet so that it becomes a termination triplet • results in truncated protein that won’t function • protein degraded in cell
what are indel (insertions and deletions) mutations
• if nucleotide base pairs ( not in multiples of 3 are inserted in or deleted from a gene, because the code is non-overlapping and read in triplets, all subsequent triplets are altered (frameshift) • protein made can’t carry out function • insertion or deletion of a triplet of base pairs result in loss or addition of an aa
what are expanding triplet nucleotide repeats
• some genes contain repeating triplets such as -CAG CAG CAG- • no of CAG triplets increases at meiosis and again from generation to generation
what are some benefits of mutations
• helped drive evolution through natural selection • blue eyes useful for seeing in less bright light • black skin has high conc of melanin protecting from sunburn + skin cancer
what are some neutral mutations
• inability to smell certain flowers • differently shaped earlobes
define exon
the coding, or expressed, region of DNA
define intron
non-coding part of DNA
define operon
a group of genes that function as a single transcription unit
what’s a transcription factor
protein or short non-coding RNA that can combine with a specific site on a length of DNA and inhibit or activate transcription of a gene
give an example of an operon in prokaryotic cells involved in the regulation of gene expression
lac operon
what can the bac E.coli metabolise instead when glucose isn’t present
lactose
what 2 enzymes does lactose induce the production of in E.coli
• lactose permease • B galactosidase
what’s the lac operon
a length of DNA with an operator region next to the structural genes lac Z and lac Y that code for the 2 enzymes
relative positioning of structures in lac operon and what they are
I | |P|lac O |lac Z|lac Y I = regulatory gene P + lacO = control sites lacO = operator region lac Y + lac Z = structural genes
what’s the role of lactose permease
allows lactose to enter the bacterial cell
what’s the role of B galactosidase
hydrolyses lactose to a glucose and B galactose