lec 17- from genes to traits Flashcards
what did Peter and Rosemary grant find out about the Galapagos finches?
-the numbers of species of finches are 18 rather than the usual 14 to 15
- an example of rapid speciation for tetrapods, which is usually rare
what are the three hypotheses behind Darwin’s finches origins?
- multiple colonizations by different finches: different species of Darwin’s finches should have their closest genetic relatives elsewhere
- single colonization: from South or Central America, the diversified into many descendant species by evolution
- single colonization from Isla De Coco and then diversification: Cocos finches should be closest relative to all Darwins finches
which hypothesis of Darwins finches origins was supported?
2, single colonization, due to darwins finches being closely related to each other than any other birds
who was Bryan Fry and what did he discover?
-Bryan Fry was a venom researcher, and he looked at the venom of multiple snakes to determine their evolutionary history
-he focused on rattlesnake venom crotamine
-crotamine is a very similar structures to defensins which are used to fight bacteria in various organs
how is crotamine delivered and what are the three other types of toxins?
-crotamine is delivered through hollow fangs
-Cytotoxins: tissue destruction
-Neurotoxins: nerve damage, paralysis
-Hemotoxins: blood clots
what is the only venomous lizard in the USA?
Gila Monster, has venomous mucous delivered from biting and chewing
where did the venom gland come from?
the venom gland is a modified salivary gland and the venom is modified saliva
was the original defensin based venom strong in effecting prey?
no, most likely had minor effects but more mutations over time led to enhanced effects which were selected for
what are the snake organs where venom genes (crotamine) act?
brain, heart, pancreas, liver, kidney
how does gene duplication of B-defensins occur?
-pancreas expresses single copy of defensin gene
-duplication of defensin gene
-change in regulation makes duplicated copy expressed in mouth rather than pancreas
-additional duplications and losses as venoms diversify in different lineages
what does a mutation in duplicated genes of defensins produce?
-venom proteins (crotalins) in the mouth and salivary or mucous glands of snakes
-crotalins are crotalus venom consisting of crotamine proteins
did venom evolve in lizards before snakes?
yes, even though ancestral lizards did not have venom
what do common garter snakes of BC produce even though they are non-venomous?
toxins (crotalins)
what is the starting point for novel traits?
-promiscuous proteins like defensins
-duplication leads to new functions
why can duplicated genes accumulate mutations rapidly?
because they are usually hidden from purifying (negative) selection
what is gene recruitment?
exaptation
what does evolution and development (Evo Devo) include?
genetic toolkits and regulatory networks control development of phenotypes
how does lactose help in gene regulation? explain the mechanism
-when lactose is not present, the beta-gal gene is repressed, polymerase is blocked by repressor protein and cant transcribe mRNA
-when lactose is present, it binds to repressor protein and changes its shape, allowing polymerase to transcribe mRNA
can a series of different repressors and promoters cause a cascade?
yes
what are Hox genes?
the patterning genes that control development of body plans in most multicellular animals
what is Evo Devo?
study of regulatory genes and their effects on phenotypes and changes during evolution including new adaptations
does the same underlying network of ancient regulatory genes control body forms in most organisms?
yes
what genetic cascade/gene patterns the legs in flies and mice?
DLL = distalless gene
changes in a single gene can cause limb elongation, which affected genes cause limb changes in cockroaches and bats?
cockroach: high levels of DPP cause long hind legs
bat: high levels of BMP2 cause long limb while short levels cause short limbs
what are orthologs?
homologous genes in different species with similar effects, like the DPP in cockroaches and BMP2 in bats)
what does an increased expression of regulatory genes cause (Hox genes)?
elongation
what does a reduction in Shh (sonic hedgehog) gene cause?
blocks hind limb formation
what two genes are likely involved in the snakes evolution being increased number of vertebrae with reduced fore and hind limbs?
DLL and Shh
what is Darwins abominal mystery?
the origin of flowering plants
when was the earliest flower fossil?
during the cretaceous, which had radial symmetry
what is the difference between early fossilized and living angiosperms?
early: radial symmetry
living: bilateral symmetry
what genes cause bilateral symmetry and what happens when disabled?
CYC and DICH genes cause bilateral symmetry when expressed, when disabled it cause radial symmetry
why is bilateral symmetry more common now?
-because its better for insect pollination
-symmetrically enhancing some petals in size, shape, and color increases attractiveness for pollinating insects
what species of flowering plant makes its lip look and smell like a pollinating digger wasp?
the Eurasian orchid
was bilateral symmetry evolved from multiple ancestors?
yes, an example of a polyphyletic adaptation
