Question

If you compare the histone modifications at the imprinting center on the maternal and paternal chromosomes, you would expect to see ____________ on the maternal chromosome and ____________ on the paternal chromosome.
a. activating marks like H3K9 acetylation; silencing marks like H3K9 methylation
b. silencing marks like H3K9 methylation; activating marks like H3K9 acetylation

Answer 1

Answer:

b. silencing marks like H3K9 methylation; activating marks like H3K9 acetylation

Explanation:

Genomic imprinting is an epigenetic phenomenon that leads to parent-of-origin-specific monoallelic expression, thereby genes under imprinting are differentially expressed depending on their parental origin. Genomic imprinting involves DNA methylation, histone modification such as histone 3 lysine 9 methylation (H3K9) and non-coding RNA regulatory epigenetic pathways, which act together to silence one parental gene form or 'parental allele'. Maternal imprinting occurs when the maternal allele is silenced (usually caused by methylation of the maternal allele), whereas paternal imprinting occurs when the paternal allele is silenced (methylation of the paternal allele). Moreover, H3K9 acetylation is connected with active promoters (gene transcription). The imprinted genes are generally grouped in genomic regions called imprinting centers (ICs) that regulate gene expression according to the parental origin.