why is the genetic code degenerate
because there are 64 different DNA triplets but they only code for 20 different amino acids. therefore each amino acid is coded for by more than one triplet
what are the types of point mutation
silent mutation
non-sense mutation
mis-sense mutation
what is silent mutation
when the substitution of a base still codes for the same amino acid. Possible due to the degenerate nature of the code
what is non-sense mutation
when the substitution of a base leads to a premature ‘stop codon’ being coded for
what is a mis-sense mutation
when the substitution of a base codes for a different amino acid
how is the effect of a mis-sense mutation determined
determined by the role of the amino acid in the final polypeptide
what is frameshift
the insertion or deletion of a nucleotide results in a frameshift
what are beneficial mutations
mutations that offer a selective advantage to the individual
what are neutral mutations
if the mutation occurs in the non-coding part of the DNA or is a silent mutation
can the environment play a role in whether a mutation is advantageous
yes
how is sickle cell anaemia caused
- Haemoglobin - a globular protein with 2 alpha polypeptide chains and 2 beta polypeptide chains
- a mutation in the gene coding for the beta chain causes sickle cell anaemia
what does beta galactosidase do
catalyses the hydrolysis of lactose into glucose and galactose
what does lactose permease do
transports lactose into the bacterial cell
what do the structural genes of the lac operon do
encode proteins involved in the uptake and utilisation of lactose
what do the regulatory genes of the lac operon do
encodes a protein which controls when the structural gene is expressed
what part of the lac operon codes for the beta galactosidase
lacZ
what part of the lac operon encodes the lactose permease enzymes
lacY
what does lac A code for
beta galactosidase transacetylase
what does beta galactosidase transacetylase do
adds an acetyl group to the B-galactosidase
what is the role of RNA polymerase in the lac oepron
it binds to the promoter region of the lac operon to initiate the transcription of a gene
do the structural genes in the lac operon turn on when lactose is present
yes
do the structural genes in the lac operon turn on when lactose is absent
no
what happens in the lac operon when lactose is present
- when lactose is present, it binds to the lactose-binding site of the repressor protein
- this changes the shape of the DNA binding site so it can’t bind to lacO
- the means that the RNA polymerase can bind to the promoter region and structural genes can be transcribed
what happens in the lac operon when lactose is absent
- the lacI is transcribed by RNA polymerase and transcribed to produce a repressor protein
- the repressor protein has 2 active sites - one site binds to lactose and the other binds to the lacO
- when lactose is absent, the repressor protein binds to lacO
- this blocks the promoter region so RNA can’t bind to it and the structural genes can’t be transcribed
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2.1.1 - cell structure88
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2.1.2 - biological molecules91
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2.1.3 - nucleotides and nucleic acids31
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2.1.4 - Enzymes30
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2.1.5 - biological membranes33
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2.1.6 - cell division, cell and organisation63
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3.1.1 - exchange surfaces88
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3.1.2 - transport in animals81
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3.1.3 - transport in plants42
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4.1.1 - communicable disease23
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4.2.1 - biodiversity47
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4.2.2 - classification and evolution28
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5.1.1 - communication and homeostasis36
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5.1.2 - excretion94
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5.1.3 - neuronal communication0
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5.1.4 - hormonal cummunciation57
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5.1.5 - plant responses6
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5.1.5 animal responses0
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5.2.1 - photosynthesis34
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5.2.2 - respiration72
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6.1.1 - cellular control28
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6.1.2 - patterns of inheritance46
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6.1.3 - manipulating genomes0
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6.2.1 - cloning + biotechnology49
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6.3.1 - ecosystems55
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6.3.2 - populations and sustainability25
