Provide definitions/explanations for the following terms: $1$. Histone octamer,$2$. Euchromatin.

(N/A) $1$. $Histone$ $octamer$: Histones are positively charged basic proteins that are organized to form a unit of eight molecules,known as a histone octamer. The negatively charged $DNA$ is wrapped around this positively charged histone octamer to form a structure called a nucleosome.
$2$. $Euchromatin$: In a typical nucleus,some regions of chromatin are loosely packed. These regions stain light and are referred to as euchromatin. Euchromatin is considered transcriptionally active chromatin because the $DNA$ is accessible for the transcription process.