If your biological parents are unrelated to one another, you probably have about
ID: 70238 • Letter: I
Question
If your biological parents are unrelated to one another, you probably have about 3,000,000 sites in your genome that contain a single nucleotide difference between maternal and paternal chromosomes. SNP arrays have been designed to survey about 500,000 of the most commonly variable sites across the genome, and they can detect whether you contain allele A, allele B, or both, as well as the copy number of each allele. If any segmental deletions or duplications exist in your genome, they would be detected by changes in copy number and allele frequency for all SNPs within a genomic segment. Please describe how your SNP arrays would appear if your biological parents were biological brother and sister (this happened by accident in England a few years ago between siblings who grew up in different families). [Hint: you should pay attention to the distribution and copy number of the alleles.]
Explanation / Answer
SNP arrays contain high density probes which can detect single nucleotide polymorphisms (SNPs).and are useful in identification of gene copy number variation (CNVs) and Regions of homozygosity (ROH). The calculated estimated coefficient of inbreeding (F) represents the parental consanguinity. For a child born out of bother sister mating, the F will be F1/4 and will have greater than 20% of ROH and can be detected using SNP arrays. The genome of the child will show Uniparental disomy (UPD) and ROH larger than 5 Mb can be seen. The distribution of alleles will be same in the child as similar copies he will receive from both father and mother. The SNP array of the child will show larger homozygous regions in the genome. SNP array also reveals the copy number variations and is associated with birth defects and autosomal recessive disorders.