Genome Evolution Flashcards
True or False: Would you expect a ‘simple’ or a small organism to have a small genome?
False.
True or False: Are introns useless
False.
Why do people suspect introns may be adaptive or beneficial?
Selective pressure.
They allow for the rearrangement of genomes. They put a lot of energy into splicing. They are tightly conserved in their position.
Where do new genes come from?
Gene duplication
How do host genomes defend against mobile genetic elements? (explain this in terms of post-transcriptional and pre-transcriptional silencing)
Transposomes can silent genes.
Why are mobile genetic elements considered genome parasites? Can you think of any situations in which mobile genetic elements might be advantageous to the individual?
Transposons (mobile genetic elements): translocate genetic information in the genome; they can jump from one chromosome to another
Example: Antarctic Eel
Explain how a mobile genetic element’s fitness might be high, while its’ host’s fitness might be low
Transposome are tiny pieces of DNA doing their own thing in the host which is bad for me but beneficial for the genome.
Know the Roma tomato example of a mobile genetic element resulting in a new phenotype
Phenotype: elongation due to mobile genetic element
Why do eukaryotes have such a gigantic genome?
They have inner region genomes that don’t code for anything. They also have introns and extrons.
How does segmental duplication happen?
There is a duplication of small sections of the genome. This can also occur with mobile genetic elements or unequal crossing over.
Why do we mostly study large phenotypic effects of single mutations?
It’s easier to pinpoint mutations
What can happen to a duplicated gene? How can subfunctionalization lead to an escape from adaptive conflict? (i.e. know the Lycodichthys example!)
One of the duplicate copies could stop working; functionalization
Both copies could keep working; gene conservation
I
n neofunctionalization, once the duplication happens one copy acquires a new function and can do a new task
In subfunctionalization, the original gene had two functions; the gene duplicated; instead of both copies doing both functions - they each specialize.
In some cases, a single gene is doing two things - sometimes it gets good at doing one thing without affecting the other. When subfunctionalization occurs, each individual can do one function really well.
Know examples of adaptations arising from new mutations and from existing alleles present @ low freq.
Adaptation from new mutation: Tetrodotoxin(from newts) resistance in garter snakes
Adaptation from standing variation: Stickleback Eda alleles (plate and speed phenotypes)
Freshwater had low-plate phenotype while marine had complete-plate phenotype.
