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17 Cards in this Set
- Front
- Back
- 3rd side (hint)
Homeotic mutations? |
mutations which result in the transformation of one body structure or another
Structures are often perfectly formed, just in wrong place |
Homo same
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Hox gene? |
family of genes that encode related transcription factors
characterised by containing a DNA binding domain called the homedomain/ homeobox
highly conserved in evolution
shown to be involved in anterior posterior patterning in dropshilia and other organisms
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what do the clusters of the hox genes in the genome show? |
the clusters show spatial and temporal relationships
genes in the 3' end are expressed before those in the 5' of the cluster |
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homologous genes? |
genes that share a common ancestoral gene |
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paralogous genes? |
genes that have been duplicated within a single genome
pairs and pairs in same genome |
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orthologous genes? |
same genes in different organisms
others have same |
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Gene redundancy? |
a situation where no change in phenotype is observed when a gene is mutated
this is because another gene (usually a paralouge) can replace the function of the mutated gene
thus the presence of a paralogous gene masks the presence of the mutated one
this kind of interaction is known as using one of the genes available in the genetic toolkit of the organism |
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how can dev biol use genetics to identify genes involved in development|? |
when a mutation causes a disease phenotype to occur it can show what the mutated gene is responsible for
if a mutation results in loss of eye function, that gene is responsible for normal eye functioning
not that: often name for a gene is its loss of function phenotype |
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how can genes duplicate? |
1) Tandem gene duplication: where a gene is replicated many times,
2) Segmental duplication: affects large portions of the chromosome ( like giant tandem duplication)
3) Whole genome duplication events
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In which ways can whole genome duplication events occur? |
1) Allotetraploidy = hybridisation between two seperate species (allo-diff)
2) Autotetreploidy = single individual ( duplication of genome through improper meiosis)
autotetraploidy can only occur if diploid state is maintained, so haploid gametes can be produced |
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what normally happens to a gene that has been replicated? |
the genes is normally removed unless it gains a new function- subfunctionalisation
duplication and diverge |
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what are the mechanisms for subfunctionisation of a duplicated gene? |
1) change protein sequence of product
new protein has new function, different binding etc
2) Change time / place of expression
cis regulatory regions are also duplicated, somehow these are changed, altering when and where these genes are expressed
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how have the hox genes co-opted in the mammalian genome?
has thier function been conserved at all? |
responsible for limb patterning in mammals
genes expressed in anterior of drosphi also expressed in anterior of mouse, same for posterior
their function has been somewhat conserved
now also involved in proximal-distal development of limbs |
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Once gene has subfuntionalised, does it loose its original function? |
note subfunctionalisation is also refered to as the aquisition of novel functions
often it does not loose its original function
it becomes part of the genetic tool kit of an organism |
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is their any correlation between hox genes and anatomical features of organisms? |
Using comparative anatomy of mouse and a chicken,
Chick has 14 cervical vert
mouse has 7,
the chick genome has many more hox genes associated with cervical vert development
Strong correlation between hox genes and anatomical features |
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How do we find out if hox genes are only markers of ant-post positioning, or if they are direction involved with A-P positioning
that they are directly involved? |
easier method is to study the effects of mutations in hox genes for mammals,
mutations in the hox genes change ant-post patterning |
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What is the issue with studying the function of hox genes, but looking at example with mutations? |
often there are more than one of each hox gene
therefore if one has a mutation, redundancy of a paralogous gene kicks in an normal function may still be maintained
therefore all paralogues of that hox will have to be removed, mutated for its functioning to be fully understood
removing all paralouges removes problem of redundancy |
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