Genetic identification of a small and highly isolated population of fin whales in the sea of cortez

[Pericles]

Hey there I'm currently studying biology at university (1st year) and we have been given a scientific paper to summarise.

 

What I need help with is finding out what 'mitochondrial and nuclear loci' are.

 

Here's the abstract - If you could explain to me what they mean by these two terms and how they are being used in finding the genetic variation of fin whales that would be much appreciated.

 

Abstract

For many years, researchers have speculated that fin whales are year-round residents in the Sea of Cortez (= Gulf of California). Previous work by Bérubé and co-workers has shown that the degree of genetic diversity among fin whales in the Sea of Cortez at nuclear and mitochondrial loci is highly reduced. However, the relatively unobstructed connection with the North Pacific Ocean argues that Sea of Cortez fin whales are part of a much larger eastern North Pacific population given the extensive migratory ranges observed in fin whales and baleen whales in general. The low degree of genetic variation might thus simply be due to historic fluctuations in the effective population size of an eastern North Pacific population. In order to test if the reduced genetic variation detected among fin whales inthe Sea of Cortez is due to small population size or a past bottleneck in an otherwise large eastern North Pacific population, we analyzed the geographic distribution of genetic variation at a single mitochondrial (control region) and 16 nuclear loci in samples collected from fin whales in the eastern North Pacific (n = 12) as well as the Sea of Cortez (n = 77). Our results showed that fin whales observed in the Sea of Cortez constitute a highly isolated and thus evolutionary unique population, which warrants special conservation measures given the current low estimate of abundance of approximately 400 individuals.

 

Thanks again.

[CharonY]

Loci in this context are simply regions on the DNA. Mitochondria possess their own DNA and mitconchondrial loci refer regions on it, where as nuclear loci refer to DNA regions in the main chromsomes (which are located in the nucleus).

[Pericles]

Thanks for your reply.

 

One more thing if it isn't too much trouble. There's a sentence - here - which I'm having trouble understanding

 

These analyses estimated high levels of

divergence between relatively distant sampling areas,

and more so at mitochondrial compared to nuclear

loci.

 

How can mitochondrial loci diverge more so than nuclear loci if the samples are from the same whale?

[CharonY]

The short version is that not all loci mutate (or maintain mutations, to be more precise) at the same rate.

[Pericles]

Oh ok.

 

And how would the varied mutation rates in each loci help explain the reduced genetic variation or any variation among fin whale populations for that matter?

 

Thanks for you help and patience.

 

EDIT: If it would help and if you want me to, I can put up more of the paper if you'd like.

Edited August 16, 2010 by Pericles