DNA methyltran Show more . 1. How are patterns of DNA methylation transmitted across cell division? DNA methyltransferases recognize hemimethylated DNA and use the methylated strand as a template to methylate the new DNA strand. DNA is replicated by conservative replication to ensure that one copy of the genome retains the DNA methylation pattern and is passed on to one of the daughter cells. 5-methylcytosine is deaminated to form uracil. The uracil is then recognized by Uracil-DNA glycosylase which corrects the base back to cytosine. A long noncoding RNA is used as a guide after DNA replication to target specific sequences for DNA methylation. Special sequence-specific DNA binding proteins methylate the DNA after it has been replicated so that the methylation pattern is replicated before cell division. 2. What is the genomic conflict hypothesis for the origin of genomic imprinting? The genomic conflict hypothesis suggests that there is an incompatibility between the genetic material contributed by the male and female parents which lead to the selective silencing of incompatible genes during embryo development. This hypothesis predicts that the maternal alleles will favor the survival and success of the offspring by promoting fetal growth while the paternal alleles will restrict growth in order to preserve the health of the female for future mating. The genomic conflict hypothesis introduces the idea that there is a struggle for survival that reaches the genetic level. The paternal and maternal copies of genes compete for dominance and the strongest alleles are expressed while the weaker alleles are epigenetically silenced. This hypothesis indicates an evolutionary relationship between the maternal and paternal genomes whereby their genes cooperate to provide the maximal growth environment for the developing fetus. This hypothesis proposes that there are different and conflicting evolutionary pressures acting on maternal and paternal alleles for genes that affect fetal growth. 3. . (Problem 23) What would be required to prove that a phenotype is caused by an epigenetic change? The phenotype must be passed to progeny only through the maternal DNA. The phenotype must be reversible in the presence of mutagenic compounds. The phenotype must result from a heritable change that is not the result of an altered nucleotide sequence. The phenotype must be unexplained by known genetic mechanisms. The phenotype must be the result of a nucleotide change that is present in one gender but not the other. Show less

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