Homology And Analogy Flashcards
What does homology mean and how does it come about?
Two structures from a common ancestor
They are formed by a common mechanism
What does analogy mean and how does it come about?
No common ancestor -> similar structures produced by selection to meet a similar function (convergent evolution)
What is a crystallin and where is it found?
A protein with no structural identity. Found in the lens.
What are the three types of crystallin?
Alpha and beta/gamma
What are alpha crystallins related too?
Beta shock proteins- recruited to the lens, but were originally found elsewhere
What are the functions of crystallins
Soluble, stable, transparent and refractive
What is a paralog (with example)?
Two genes from the same organism (by duplication)
Eg mouse hox a2, a3, a4 etc
What is an ortholog (with example)?
Two genes from different organisms (common ancestor)
Eg fruit fly gene is the orthologue of the mouse hox gene
What functions can duplicated genes take on?
Complementary functions (Redundancy) Non-overlapping functions (novel)
What happens when the hox gene is mutated in fruit flies?
The antennae turns into legs
What are hox genes?
Developmentally important transcription factors
What do hox genes do?
Bind to DNA in a sequence specific fashion and regulate the expression adjacent/nearby genes
What’s the RNA world hypothesis
Early life is thought to have been based on self-replicating, self-catalysing RNA molecules
What is a ribozyme and where is it found?
Catalytic RNA - found everywhere
Why did the RNA world evolve into a DNA genome/protein enzyme world?
DNA more stable than RNA, greater range/robustness of protein enzymes
