What does the genome tell us about being human?

Question 1

Describe/explain why we use comparative genomics

Answer 1

• to discover what is common and what is different
• things in common are called ‘conserved’ and many encode biology in common between species
• things that are different may encode organism-specific biology
• so by comparing genomes you learn a bit about which bits of the genome do what

Question 2

How do you compare sequences?

Answer 2

• by lining them up next to each other and marking each point where sequences are the same
• this is called aligning (the technology. it is all done on a computer)

Question 3

How can we compare genomes within species?

Answer 3

• by comparing genomes of individuals we can find out where differences occur
• differences might be assosciated with:
  - disease
  - characteristics of an individual
  - evolutionary history
• more and more genomes are being sequenced or mapped
• we can now sequence the human genome for US$600

Question 4

What do we learn from comparing genomes between species?

Answer 4

if we compared an organisms genome to others we can learn:
- what sort of genes they have
- how differences between species arise
- relationships between species

Question 5

What does using the DNA of dead things tell us?

Answer 5

• DNA from dead things can remain in te environment
• DNA degrades and is masked by more modern DNA
• DNA bases are also modified as they degrade, sometimes changing the sequence
• Ancient DNA can be extracted and identified in very special circumstances
• It has been used to determine the relationships of extinct animals, like moa or mammoths

Question 6

What did the scientists get from sequencing DNA from the three bones from the Denisova caves?

Answer 6

• 4 Billion Neanderthal nucleotides
• Identified and discount modern contamination
• Gathered sequence from 3 individuals (probably)
• Enough sequence to compare with modern human genome sequences from around the world
• Identified bits of DNA that differ between Neanderthals and us

Question 7

What was the best finding the scientists got from the bones in the denisova caves?

Answer 7

• some of us carry Neanderthal DNA
• Modern humans from Europe and Asia carry Neanderthal alleles
• Those from Africa show no signs of these alleles
• The most likely explanation for this was that where modern humans met Neanderthals, they interbred.

Question 8

What does the fact that some of us carry Neanderthal DNA mean?

Answer 8

• This DOESN’T mean that those of us with Neanderthal DNA have a different set of genes
• It just means that our DNA holds variants that arose in Neanderthals
• 2-4% of the genome of non-Africans is made up of variants that arose in neanderthals
• So neanderthal DNA add to the variation in our genome that might be related to our phenotype

Question 9

What did the finding of the finger bone in Denisova tell us?

Answer 9

• The mitochondrial DNA did not match Neanderthal or Modern Human DNA
• The genome from this species of archaic human was sequenced from a tooth found in the same cave in 2010
• Denisovan variation is also found in the human genome, where it makes up 4-6% of the genomes of present day Melanesians

Question 10

What does all of this history/information tell us?

Answer 10

• The sequencing of genomes has helped us to better understand who we are and where we came from
• The key technology here is being able to compare genomes
• By comparing whole genomes from multiple species we can start to understand where our characteristics come from
• This is the same approach used in modern disease genetics - data rich and statistically intense analysis
• Our extinct relatives are not just fossils in our museums, but live on as variants in our genomes which affect our biology