Background

The 23andMe V2 chip was 23andMe’s second microarray chip. It replaced their V1 chip in September 2008. It was almost surely the Illumina HumanHap550 Genotyping BeadChip.

Microarray chips test a small percentage of SNPs on the human genome. Each letter the DNA code for the human genome (A, C, T, or G) is called a base pair. This one tested a total of 550,000 SNPs. Launched in the first quarter of 2006, it was designed using SNP markers selected from the HapMap and 1000 Genomes projects. Its intended use was medial genetics association studies (GWAS).

The number of SNP variants tested by chromosome

The number of SNP variants tested by chromosome

Chromosome 23andMe V2
1 43,734
2 46,065
3 38,255
4 33,970
5 34,586
6 37,660
7 30,877
8 31,474
9 26,880
10 29,817
11 27,868
12 27,915
13 21,281
14 18,669
15 16,983
16 17,271
17 15,153
18 16,859
19 10,105
20 14,362
21 8,336
22 8,666
X 13,828
Y 1,880
mt 2,019
Autosomal Total 556,786
Total 574,513

SNPs per Million Base Pairs – Heatmap

The V2 chip tested 550,000 base pairs across the human genome. This heatmap shows how those SNPs are distributed across the 22 autosomal chromosomes and the X-chromosome. The ranges are for counts of tested SNPs in blocks of 1 million base pairs.

Created with Kitty Cooper’s Chromosome Mapping Tool