Chapter Summary

• Different genomes are inherited in different ways. In sexually reproducing taxa, most of the nuclear genome is inherited biparentally. In most animals and higher plants, mitochondrial DNA is maternally inherited. Chloroplast DNA usually is inherited maternally in flowering plants and paternally in conifers.

• Animal mitochondrial markers are popular in molecular ecology because of their lack of recombination, high mutation rate, small effective population size and readily available universal primers.

Table 2.5 Summary of some of the properties of genetic markers

Comparison of

Suitability for

Development

data between

inferring evolutionary

Overall

Genetic marker

Inheritance

Target genome

time"

Costb

studies

relationships

variability

Allozymes

Co-dominant

Nuclear

Low

Low

Limited

Limited

Low-moderate

PCR-RFLPs

Co-dominant

Nuclear Organelle

Moderate

Low

Limited

Limited

Low-moderate

DNA sequences

Co-dominant

Nuclear Organelle

Low-high

Moderate

Yes

High

Low-moderate

SNPs

Co-dominant

Nuclear Organelle

High

Moderate-high

Yes

High

Moderate

Microsatellites

Co-dominant

Nuclear Organelle

High

Moderate-high

Yes

Limited

High

RAPDs

Dominant

Nuclear

Low

Low

Limited

Limited

High

AFLPs

Dominant

Nuclear

Moderate

Moderate

Limited

Limited

High

"Assuming relevant markers have not been developed already for the species in question (or close relative). Note that some development is required for all markers. bCost here is relative, because all molecular work is expensive. Cost will be reduced if relevant markers have been developed already for the species in question.

"Assuming relevant markers have not been developed already for the species in question (or close relative). Note that some development is required for all markers. bCost here is relative, because all molecular work is expensive. Cost will be reduced if relevant markers have been developed already for the species in question.

• Plant mtDNA generally lacks recombination and has a relatively small effective population size, but mutation rates are much lower than in animals. Chlor-oplast DNA regularly undergoes recombination and therefore gene rearrangements are common.

• In mammals, the Y chromosome is the paternally inherited sex chromosome. Most of it does not undergo recombination, and the recent identification of variable regions means that this can be a useful marker for retracing male lineages.

• Obtaining data from markers with contrasting patterns of inheritance can be extremely useful for detecting past hybridization events and for differentiating between dispersal of pollen versus seeds in plants, and of males versus females in animals.

• Co-dominant markers provide locus-specific information that allows us to discriminate between homozygotes and heterozygotes and to calculate allele frequencies.

• Dominant data neither discriminate between homozygotes and heterozygotes nor provide accurate estimates of allele frequencies; however, choice of marker is affected by time, money and expertise, and initial development is often easier for dominant than for co-dominant markers.

• DNA sequence data are most suitable for inferring evolutionary histories, and SNPs are a newly emerging source of sequence data from multiple loci. Microsatellite loci are highly polymorphic and are appropriate for inferring recent events such as dispersal or mate choice, whereas multi-locus markers permit the rapid and simultaneous screening of several loci.

Was this article helpful?

0 0

Post a comment