What sequences are between adjacent genes? The human genome has a lot of non-coding regions, which include regulatory elements, repetitive DNA, and introns. Suppose there are two adjacent genes on a chromosome, and their positions on the chromosome are, say, For the first gene: 11,785,723 to 11,803,245 bp. For the second gene: 11,806,096 to 11,806,143 bp. These values **include** their regulatory elements, promoter and introns as well. So what sequence is present between bases 11,803,245 and 11,806,096? Are they satellite sequences? Is this non-coding, non-regulatory region 11,803,245 to 11,806,096 bp heterochromatin?

No. The intergenic regions are not necessarily heterochromatin. Chromatin conformations are usually very long range and are not usually confined to a single gene. The spread of chromatin state can be prevented by insulators/boundary elements), which again are not a part of the transcribed region. The intergenic regions can also harbour distal regulatory elements such as enhancers and silencers; they can have microsatellites, transposons etc too. To know what all are there in a specific region, you can look at the different tracks in the UCSC genome browser.

In short, there can be functional and/or non-functional DNA in-between the transcribed regions.

Repeat regions need not be heterochromatinized and conversely not all heterochromatic regions consist of repeats.