icrosatellites and Parental
Determination
From ovarian measurements, we can determine which wasps in the colony were capable of reproducing at the time of collection. To gain a further understanding of the social structure of the colony, it is important to be able to determine which of the reproductively capable females are the mothers of the workers. In order to do this, it is necessary to find some genetic marker which links mothers and daughters.
One such genetic marker is a microsatellite. Microsatellites are stretches of DNA that consist of tandem repeats of a simple sequence of nucleotides (for example, AAT repeated 15 times in succession). Using the polymerase chain reaction (PCR), these repeats can be easily amplified. The number of repeat units that an individual has at a given locus can be easily resolved using polyacrlyamide gels. From the gels, we can see two genetic marks for most individuals; each individual inherits one length of nucleotide repeats from his or her mother and one from his or her father (individuals with one band received the same band from both their mother and their father).
n Example of the Use of Loci Information
On the gel, we see the bands for the daughters and foundresses from colony114 at locus Pbe 424AAT. Though we do not have any genetic information from the fathers, in this species, each mother mates with only one male, so all of the daughters of one mother will have a shared band from the father. In this case, all of the daughters have a 207 band. Since neither of the foundresses have this band, we can assume that each of these daughters got this from her father. Furthermore, because they all have this same shared band, it is likely that all of the daughters has the same father, however, it is important to verify this with information from other loci. Now, daughters 10, 12, 13, 15, and 16 have a band at 204, as does foundress 20. Because foundress 19 does not have a 204 band, we can assume that foundress 20 is the mother of those daughters. Because it is likely that all of the daughters have the same father, we can guess that foundress 20 is the mother of all of the duahgters. However, the remaining daughters have band 210, which both of the foundresses have. Therefore, if we do not assume that all of the daughters have the same father, from this locus, we cannot determine the mother of those remaining daughters from the information provided by this locus. It is necessary to confirm results with and to gain further from other loci.
When determining parentage, it is important to remember not to assume too much. Remember,
- The daughters may not all have a common mother.
- If the daughters do not have a common mother, they will not have a common band from their father, unless, two fathers gave the same band.
- Be especially careful when the daughters share a common band that one or more of the foundresses also shares. This band could be caused by the mother and not by a common father.
- It is possible to have a daughter whose mother was not collected.
- An individual with only one band received the same band from her mother and her father.
Overall, parental determination is a process of elimination. It is likely that no single locus gives enough information to assign maternity for all of the daughters. Information from several loci must be pooled and analyzed in order to make an accurate parental assignment.
