Final answer:
The mechanism to imprint genes is methylation of cytosine. This process silences genes in regions called CpG islands and can be inherited by offspring, while also being influenced by environmental factors.
Step-by-step explanation:
The mechanism to imprint genes is d. methylation of cytosine. Gene imprinting involves the addition of methyl groups to specific cytosine nucleotides within DNA to modify gene expression. This typically occurs in regions of DNA known as CpG islands, mostly found in the promoter regions of genes. When cytosine is methylated, it can silence the gene, although methylation may also have other regulatory effects. Methylation patterns set during gamete development can be passed to offspring, leading to imprinted genes that maintain their silenced state through generations. Furthermore, environmental conditions can influence these methylation patterns, affecting gene expression. Histone modifications, such as acetylation and deacetylation, can interact with DNA methylation to regulate chromatin structure and gene transcription.