Chapter 19

  • Created by: Kaiya1000
  • Created on: 16-04-18 09:27
What is a mutation
change in the sequence of dna
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what are the three types of mutations
Substitution insertion deletion
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whatis frameshift mutation
insertion and deletion can lead to a change inreadingframe of bases changing successive codons
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what are point mutations
substitutions of a single codon due to the degenerate nature of dna the new codon maycode for ththe same amino acid
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what are mutagens
chemical/biological physical agent thatcauses mutations
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describe other causes of mutations
depyridimation depurination loss of purine/pyrimidine base can lead to insertion of an incorrectbase// the presence of free radicals-oxidising agentdisruppting nucleotide structure can disrupt base pairing duringdna replication
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examples of physical/chemical and biological mutagens
ionizing rays radiation like x rays/deaminating agents/viruses
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Effects of different mutations
Silent- no protein change so no effect on pheneotype may occur in introns or code for same amino acid/Nonsense-mayresult in stopcodon shorteningprotein (non functional) negative effects/Missense- result in incorporation of incorrect amino acid
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What is a conservative/non conservatiive mutatiom
conservative- amino acid change leads to protein thathassimilar properties to the original less severe effect- non conservative- newamino acid has differentproperties may cause disease
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Mutations effect on synthesised protein
Amorph- loss of protein function/ Hypomorph - reduction in protein function/ Hypermorph- gain in protein function /
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Can mutations be beneficial are there anyexamples?
yes for example the ability to digest lactose which is thought of as a recent human mutation the ability to digest milk as an adult prevents osteoporisis- most mammals are lactose intolerant
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What are the chromosome mutations
Deletion- section breaks off/ Duplication- section replicated on chromosome/Translocation- a sections breaks joins another non homologous chromosome/ Inversion- a section breaks of reverses then joins back
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why is gene regulation necessary
As the whole genome is in allnucleuses some genes are not neededby that cell so ecpression must be regulated /genes turning off and or synthesis rate increased decreased dependent on demand this prevents waste of resources/coordination of cells
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Ways theyare regulated
Transcriptional - genescan be turned on/off /Post transciptional- mRNA modified regulating translation /Translational - translation stopped/started /Post - Translational- proteins can be modified alter synthesis
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What is chromatin remodelling
Transcriptional control- dna is wound around histone proteins resulting in chromatin- hetero chromatin is tightly wound in cell division preventing transc and euchromatin is loosely wound in interphase allowing free transcr as protein syntheiss only
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Advantages of this method
prevents complex energy consuming protein sythesis from occuring during division
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What is histone modification
Transcriptional control the increase/decrease in the degree of packing accoring to adjusting the charges
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What does the addition of acetyle,phospategrous do
reduces positive chargeon histones so they are more negative dna coils less allowing certain genes to be transcribed
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what odoes the addition of methyl groups do
makes histones more hydrophobic so theynind tighter preventing transcription
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What is a lac operon
operon is a group of genes under the control of the same regulatory mechanism it is efficient as genes can be turned off / the lac operon is a group of three genes invlved with metabolism of lactose
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structures on the lac operon
threestructural genes coding for enzymes (lacz,lacy,laca) a regulatory gene lacI near operon codes for repressor protein preventing transcription, operator region is close ton the genes
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Cyclic AMPs role
rna polymerase binding has a slow transcriptionalrate that needs to increase to produced required quantity - binding of cAMPreceptor protein increases this - glucose into E.coli decreases cAMP reducing transcription of genes to metabolise lactose
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whwhat is rna processing
post tansc/pre transl - pre mRNA is modified to make mature mRNA with a cap adddded to 5' end (modified nucleotide and tail of adenine nucleotides added to 3' which helps stabilise RNA delaying degradgtion /Splicing to take out introns to join exon
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What is rna editing
addition deletion/substitution of nucleotides resulting in production of different proteins increasing range of proteins from a single mRNa GENE
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Describe translational control
regulating protein sythesis by : degradtion of mRNA the more resistant the molecule the longer it lasts /binding of inhibitory proteinsprevent ribosome binding/activation of initiation factors which aid binding of mRNA to ribosomes
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what are the Post translational control
addition of non protein groups like carbohydrate chins/modifying amino acids /folding shortening proteins/ modification by cAMP
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what are homeobox genes
group of genes containing the homeobox a section of dna that is highly conservesd in animals/plant fungi
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Give an example of a homeobox gene
Pax 6 - when mutated causes blindnessin humans and mice/fruit flies gene disruption also causesblindness so it is involved in eye development
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what are hox genes?
also knon as homeobox genes are reponsible for the correct positioning of body parts the order the genes appear on chromosome is the order effects are expressed
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how are body plans represented
ascross sections showing arrangent of tissues
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what does diploblastic and tripoblastic mean
two primary tissues layers and three primary tissue layers
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what isthe common feature of animals
segmentation that have multiplied and are specialised for functions
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how do things develop from the embryo
somites- aresegments in the embryo they are directed by hox genes to develop in a particuolar way
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Whatare the types of symmetry found in animals
Radial- noleft/right isdesseen in diploblastic animalsBilateral - seen in mostanimals leftand rights and head and tail involved/ Assymetry- no line of symmetry
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The importance of mitosis and apoptosis
help shape organisms - mitosis increases number of cells apoptosis removes unwanted cells - apoptosis cells canalso release cchemical signals stimulating mitosis - hox genes regulate both processes
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what affects exprssion of regulatory genes
both internal/externaaal can put stress on the homeostatic balance temperature/light psychological stress/ these will have impact during growth and development of organisms
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what are the three types of mutations


Substitution insertion deletion

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whatis frameshift mutation


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what are point mutations


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what are mutagens


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