lecture 6

Question 1

Where and when did modern humans originate?

Answer 1

Around 300, 000 years ago in Africa

Question 2

Name three characteristics that generally define a population.

Answer 2

3 characteristics that define a population: Geographical proximity, a common language and shared ethnicity, culture, religion

Question 3

What were the main findings of Richard Lewontin’s 1972 study regarding patterns of genetic variation within and between populations?

Answer 3

The mean proportions of variation within populations was 85.4%
8.3% variation was observed between populations within races
6.3% variation was observed between races

Question 4

What major conclusion did Richard Lewontin make about race?

Answer 4

There is virtually no genetic or taxonomic significance of differences between “races” so the term is useless

Question 5

The migration of modern humans from Africa explains why we observed clinal patterns of genetic diversity throughout the world. Scientists have also observed that individuals can cluster together into groups. Can you explain why we observe this latter pattern of diversity?

Answer 5

There can be a clustering pattern in groups because of geographical barriers separating the populations so the larger the distance between genetic similarity.

Question 6

What are two differences between common and rare variants?

Answer 6

Common variants (>1%): are older because it takes time for alleles to increase in frequency and are generally shared between all populations
Rare variants (<1%): are at a lower frequency and are younger because there has been less time for them to spread or be deleted, so they tend to stay in a single group or population

Question 7

What is the ExAC database? Where was this resource developed. Why is it important? Give me a detailed reason and use an example to further illustrate your point of view (hint: watch the video).

Answer 7

ExAC database: looking at genetic variation on exomes of worldwide populations
It was developed at the Broad Institute
Important because now we could tell whether a variation was rare or common in a population. This is mainly used in clinical setting where patients get genetic testing done and doctors want to know how common the variant is in which ancestral group, and which are more likely to be loss of function variants. Its been a huge help to diagnose rare disease patients
*Example: *genetic testing can help confirm and deliver diagnosis that otherwise couldn’t be confirmed like for Monkol Lek where it took over a decade to diagnose him with muscular dystrophy so now, he can be proactive about his disease and getting treatment