What does the genome tell us about being human?

Question 1

What is comparative genomics used for?

Answer 1

• To discover what is in common and what is different
• Things in common are called ‘conserved’ and may encode biology in common between species
• Things that are different may encode organism specific biology
• So by comparing genomes you learn a little about which bits of the genome do what

Question 2

How do you compare individual genome sequences?

Answer 2

• By lining up next to each other and marking each point where sequences are the same
• This is called ‘aligning’

Question 3

Why would we compare the genome of species to others?

Answer 3

By comparing genomes between individuals we can find out where difference occurs
Differences such as:
- Disease
- Characteristics of an individual
- Evolutionary history

Question 4

What could we learn about an organism if we compare its genome with others?

Answer 4

• What sort of genes they have
• How differences between species arise
• Relationships between species

Question 5

What animals are the closest relatives of humans?

Answer 5

Chimps and bonobo

Question 6

What is a neanderthal?

Answer 6

• Probably the closest relatives of modern humans.
• Lived 130,000 - 30,000 years ago in Europe and Asia
• Unsure of why they died
• Good remains for DNA extraction

Question 7

What did they get when trying to sequence the neanderthal DNA?

Answer 7

• 4 billion nucleotides
• Identified and discount modern contamination
• Gathered sequence from 3 individuals
• Enough sequence to compare with modern human genome sequences from around the world
• Identified bits of DNA that differ between neanderthals and us

Question 8

What did they find out when they sequenced the neanderthal DNA?

Answer 8

• Some of us carry neanderthal DNA
• Modern humans from Europe and Asia carry neanderthal
• Those from Africa show no signs of these alleles
• The most explanation for this is that where modern humans met neanderthals, they interbred.

Question 9

How much neanderthal DNA do non-Africans hold?

Answer 9

2-4%

Question 10

What do the neanderthal variants in our DNA do?

Answer 10

That it adds variation to our genome that may be related to our phenotype

e. g. GG at a particular locus - more likely to get sunburnt as a child (arose in neanderthals)
- Variation gained from neanderthals affect the phenotype of humans.

Question 11

Were only homo sapians and neanderthals sequenced?

Answer 11

No, a finger bone whose mitochondrial DNA doesn’t match neanderthal or modern human DNA

• The genome from this species of human was sequenced from a tooth found in the same cave in 2010
• This is a denisovan

Question 12

Do human genomes contain Denisovan DNA?

Answer 12

Denisovan variation is also found in the human genome, where it makes up 4-6% of the genomes of present-day melanesians (east asia)

Question 13

What hybrid human species was found? What does this tell us?

Answer 13

A Neanderthal Denisovan hybrid

- Evidence for inbreeding in ancient human species

Question 14

What does studying the genomes of other human species tell us?

Answer 14

By studying the genomes of homo sapiens and our ancient extinct relatives we can build and understanding of our evolutionary history

Question 15

Why is it hard to make a genome sequence of our closer relatives (ancient human species)?

Answer 15

• DNA from dead things can remain in the environment
• DNA degrades and is masked by more modern DNA
• DNA bases are also modified as they degrade, sometimes changing the sequence
  It can be extracted and identified in very special circumstances