Evolutionary Genetics/rna World Flashcards
What 3 things do all organisms have in common
Rna
Dna
Proteins
What does Luca stand for
Last universal common ancestor
What does the RNA world help explain
What came first before dna and proteins as they can’t co exist without one another but rna can self replicate and also can catalyse
What gives rna flexibility to be able to perform many roles eg spliceosome, hammerhead ribozyme
The base catalyses hydrolysis can cause chemical flexibility and the fact it’s single stranded it can make many shapes
What 2 main functions does rna have
Bio catalyst and stores information eg encoding for proteins
Name the functions rna has including what it produces and their catalytic function
1- ribozymes 2- sirna and mirna in gene expression 3- rrna for ribosomes 4- trna for translation 5- spliceosome
What are ribozymes job and give an example of a ribozyme
They rearrange phosphodiester bonds in themselves and other molecules (cleave rna)
Eg hammerhead
What is rrna function
Makes peptide bonds
Main principle of RNA world
What was rnas first function discovered showing the possible RNA world due to catalytic activity
They found in a unicellular organism that their rrna was self splicing
Therefore identifying the spliceosome
What does ribozymes do in virusoid replication?
Cleave the rna into smaller pieces
How does hammerhead ribozymes cleave peptide bonds
The loop on 1 of the helixes disappears this allows for the bases to form base pairs with rna molecules to be cleaved
Why do we cleave rna?
Target viral rna
Target means encoding cancers
What is the use of SELEX
Identify what rna can bind with and identify different catalytic activities of rna
Explain the process of selex
A pool of rnas are bound with a target molecule
This is then washed so target /complementary rna is still attached
These rna clusters are then amplified
They can then sequence them or mutate them so that they can be modified to bind to target much better in next cycle
What did selex find rna could do that proteins now have evolved to do showing could’ve been an RNA world
Showed they could ligate nucleotides together (production of dna)
What are aptamers
Molecules generated from rna and selex that bind to specific targets
What have aptamers been used for
Drug targeting agents. Eg they produce targets on cancer cells for drugs
How are rna ‘switches’
Molecules in rna can bind to other and change conformation
Or
They can perform phosphorylation
What things are used to study when microbes were around
Fossil stomatolites
What does tree of life use to compare how closely related organisms are
Base sequences from common genes/ proteins such as cytochrome C
And also SSUrrna
SSrrna has sequences that vary in species but some conserved sequences. Why are some sequences conserved in evolution
Strong negative selection against the changing sequences
What 2 ways can you root the tree (beginning of a phylogenetic tree)
Use an out group species that doesn’t belong in other categories
Using gene duplication events which occurred in last ancestors of all 3 domains
What did the gene duplication of the elongation factor protein find?
Eukaryotes ascended from archaea. They are thus not a primary domain only prokaryotes and archaea are
Which archaea group was found most closely related to eukaryotes due to their cell components and proteins such as topoisomerase
Asgard archaea
Why are eukaryotes genomic chimeras
Because they have genes similar to archaea
And their mitochondrial genome has bacterial genes in it from the endosymbiont proteobacterium
Do eukaryotes only have the mitochondrial bacteria genes or are there genes from lateral transfer we also have?
Yes. Many genes come from different bacteria from lateral gene transfer
What are the 2 models of the origins of Homo sapiens from homo erectus
1- multi regional model : suggests Homo sapiens arouse from many homo erectus populations at once (interbreeding)
2- out of Africa model: Homo sapiens originated in Africa and then migrated (gene flow) and displaced the homo erectus WITHOUT INTERBREEDING
How is it possible to compare sequences of humans from different populations?
Because when isolated, gene frequency /allele freq will change (genetic drift) causing differences
These differences can be observed when migrate and gene flow occurs
= mapping of gene flow and interbreeding
What dna was used to first study where the first human ancestor came from
Mitochondria and it supported out of Africa hypothesis
How is PCR used to test whether interbreeding occurred between Neanderthals and Homo sapiens
Can amplify the dna and compare human sequences
Found no evidence of interbreeding due to genetic distinction between them
It is possible that some human populations eg Europe Asia populations are closer related to Neanderthals than Africans. How do we find this out
Comparing the SNPs with the 2 different human populations and homo erectus. Found closer relation with eurasia than Africa possibly due to isolation of African population
