Biology 9700 · AS & A Level · Principles of genetic technology
Principles of genetic technology — practice question
The blackcap, Sylvia atricapilla, is a small song bird. It visits parts of northern Europe in summer, where it reproduces.
A large number of blackcaps spend the winter (overwinter) in southern Europe, especially in Spain. Because many people leave food out for garden birds, some birds are able to get through the winter in the UK.
Scientists compared the genetic variation among blackcaps from two woodland sites in Germany that were 800 km apart. At both sites there were birds that had overwintered in Spain and birds that had overwintered in the UK. The measurements were taken soon after the birds came back from their winter feeding grounds.
(a)[4]
Explain how DNA sequencing may be used to measure the genetic variation of birds.
(b)
The measurements of genetic variation indicated that:
• birds that overwinter in the same country (Spain or the UK) shared many alleles, even though they were 800 km apart in Germany during summer
• birds that overwintered in different countries (Spain or the UK) shared fewer alleles, even though they were in the same forest in Germany during summer
• the genetic differences between the birds that overwinter in Spain indicate that they no longer breed with those that overwinter in the UK.
(c)[4]
Explain how these blackcaps could evolve into two distinct species.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “DNA made single-stranded by denaturation” …