Evolutionary Genetics/rna World

Question 1

What 3 things do all organisms have in common

Answer 1

Rna

Dna

Proteins

Question 2

What does Luca stand for

Answer 2

Last universal common ancestor

Question 3

What does the RNA world help explain

Answer 3

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

Question 4

What gives rna flexibility to be able to perform many roles eg spliceosome, hammerhead ribozyme

Answer 4

The base catalyses hydrolysis can cause chemical flexibility and the fact it’s single stranded it can make many shapes

Question 5

What 2 main functions does rna have

Answer 5

Bio catalyst and stores information eg encoding for proteins

Question 6

Name the functions rna has including what it produces and their catalytic function

Answer 6

1- ribozymes 
2- sirna and mirna in gene expression
3- rrna for ribosomes 
4- trna for translation
5- spliceosome

Question 7

What are ribozymes job and give an example of a ribozyme

Answer 7

They rearrange phosphodiester bonds in themselves and other molecules (cleave rna)

Eg hammerhead

Question 8

What is rrna function

Answer 8

Makes peptide bonds

Main principle of RNA world

Question 9

What was rnas first function discovered showing the possible RNA world due to catalytic activity

Answer 9

They found in a unicellular organism that their rrna was self splicing

Therefore identifying the spliceosome

Question 10

What does ribozymes do in virusoid replication?

Answer 10

Cleave the rna into smaller pieces

Question 11

How does hammerhead ribozymes cleave peptide bonds

Answer 11

The loop on 1 of the helixes disappears this allows for the bases to form base pairs with rna molecules to be cleaved

Question 12

Why do we cleave rna?

Answer 12

Target viral rna

Target means encoding cancers

Question 13

What is the use of SELEX

Answer 13

Identify what rna can bind with and identify different catalytic activities of rna

Question 14

Explain the process of selex

Answer 14

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

Question 15

What did selex find rna could do that proteins now have evolved to do showing could’ve been an RNA world

Answer 15

Showed they could ligate nucleotides together (production of dna)

Question 16

What are aptamers

Answer 16

Molecules generated from rna and selex that bind to specific targets

Question 17

What have aptamers been used for

Answer 17

Drug targeting agents. Eg they produce targets on cancer cells for drugs

Question 18

How are rna ‘switches’

Answer 18

Molecules in rna can bind to other and change conformation

Or

They can perform phosphorylation

Question 19

What things are used to study when microbes were around

Answer 19

Fossil stomatolites

Question 20

What does tree of life use to compare how closely related organisms are

Answer 20

Base sequences from common genes/ proteins such as cytochrome C

And also SSUrrna

Question 21

SSrrna has sequences that vary in species but some conserved sequences. Why are some sequences conserved in evolution

Answer 21

Strong negative selection against the changing sequences

Question 22

What 2 ways can you root the tree (beginning of a phylogenetic tree)

Answer 22

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

Question 23

What did the gene duplication of the elongation factor protein find?

Answer 23

Eukaryotes ascended from archaea. They are thus not a primary domain only prokaryotes and archaea are

Question 24

Which archaea group was found most closely related to eukaryotes due to their cell components and proteins such as topoisomerase

Answer 24

Asgard archaea

Question 25

Why are eukaryotes genomic chimeras

Answer 25

Because they have genes similar to archaea

And their mitochondrial genome has bacterial genes in it from the endosymbiont proteobacterium

Question 26

Do eukaryotes only have the mitochondrial bacteria genes or are there genes from lateral transfer we also have?

Answer 26

Yes. Many genes come from different bacteria from lateral gene transfer

Question 27

What are the 2 models of the origins of Homo sapiens from homo erectus

Answer 27

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

Question 28

How is it possible to compare sequences of humans from different populations?

Answer 28

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

Question 29

What dna was used to first study where the first human ancestor came from

Answer 29

Mitochondria and it supported out of Africa hypothesis

Question 30

How is PCR used to test whether interbreeding occurred between Neanderthals and Homo sapiens

Answer 30

Can amplify the dna and compare human sequences

Found no evidence of interbreeding due to genetic distinction between them

Question 31

It is possible that some human populations eg Europe Asia populations are closer related to Neanderthals than Africans. How do we find this out

Answer 31

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