Question

The human gene Trl is maternally imprinted. Hannah has a heterozygous genotype include one wildtype allele and one copy of the mutant “1” allele, Trl⁺Trl¹. Hannah expresses the mutant allele. Describe the methylation pattern of Trl alleles in Hannah’s somatic cells and in her gametes.

Answer 1

• Epigenetic modification established during gametogenesis regulate transcripption and other nuclear processes in gametes, but also have influences in the zygote, embryo and postnatal life.
• For DNA methylation which,, established at discrete regions of the oocyte and sperm genomes, governs genomic imprinting.
• Epigenetic marks are a fundamental component of the mechanisms that functionally interpret DNA sequence. DNA methylation involves the trasfer of a methyl group from S-adenosyl-L-methionine to a cytosine residue. The process is catalyzed by DNA methyltransferases in two distinct modes. During cell division, replication of a methylated DNA sequence creates hemimethylated CpG dinucleotides, where methylation is found only on the original starnd and is absent from the newly synthesized strand.
• DNA methylation establishment in the germline is of particular importance, as methylation marks established in the gametes have the potential to regulate gene expression in the next generation.
• DNA methylation in gametes was studied largely from the point of view of imprinted germline differentially methylated regions or imprinted gDMRs.