Final answer:
In eukaryotic cells, H2A-H2B histone complexes are involved in regulating gene transcription by packaging DNA and affecting chromatin conformation. Chemical modifications of these histones can determine whether genes are activated or silent.
Step-by-step explanation:
In eukaryotic cells, when genes are not being transcribed, the DNA is tightly packaged around charged histone proteins to form nucleosomes. The DNA-histone complexes, including H2A-H2B, are regularly spaced and play a role in regulating gene transcription. Chemical modifications such as acetylation and methylation of histones can affect the conformation of chromatin and influence whether genes are activated or silent.