Number of exon 3 class I MHC sequences found in individuals (labeled 1–10) from two different island populations of house sparrow in northern Norway. Stage and year of marking indicates whether the bird was juvenile (J) or adult (A) in the year it was first ringed, where year is given by two digits (e.g., 03 = 2003). Birds ringed as adults March 2007 (i.e., A07) were most likely recruits from the 2006 cohort (see e.g., Jensen et al. 2008). Blood samples (mRNA and gDNA) for MHC genotyping were collected in March 2007 for all individuals, thus all individuals were adults at the time of sampling. Sequences indicated in parentheses have been obtained from gDNA, while those without have been obtained from cDNA. The minimum number of loci within a given individual is determined from the total number of different sequences (gDNA and cDNA) in an individual divided by two. The letter after the sequence name indicates whether the sequence is 233 bp (S = short) or 237–240 bp (L = long) long