Introduction
DNA makes up the genetic material for all organisms. However, not all organisms have distinct molecules working with DNA that come together to make up chromatin. Chromatin is only found in eukaryotic cells, the cellular makeup of multicellular organisms. The structure of chromatin is composed of DNA and histones, together making up nucleosomes, and other non-histone proteins that bind to the DNA. The backbone of DNA is negatively charged and histones have a positive charge allowing abundant interaction between the two molecules to organize and package multitudes of DNA at multiple levels, which must fit into an extremely tight space, in a way that allows gene regulation as well. Each of the pieces that make up chromatin structure …show more content…
This modification by DNA methyltransferase places a methyl group on the cytosine, one of the four nucleotide bases that make up the structure of DNA. Most of the time, methylation occurs on cytosines that are followed by a guanine known as CpG methylation. Since CpG sequences are concentrated upstream of genes in promoter regions of multicellular organisms, methylation of these sequences can effect gene expression greatly. When genes are active, CpG islands methylation levels are low, but when they are turned off, levels are high. Therefore DNA methylation is an inhibiting or gene silencing modification to chromatin structure. When DNA becomes methylated it attracts several proteins including MECP2 and MBD1 which recruits histone modifying enzymes to remove acetyl or add methyl modifications on histone tails. This allows the open chromatin to condense as nearby histones fold to block transcription from occurring. DNA methylation can interfere with recognition and binding of positively acting transcription factors also accounting for its inhibitory nature. There are three types of DNA methyltransferase (DNMT) enzymes that can be recruited when methylated histones bind chromodomain proteins. DNMT1 acts to improve DNA methylation maintenance and DNMT3A and DNMT3B acts to methylated unmethylated DNA. As with the histone modifying enzymes, studies show that deletion or mutated DNA modifying enzymes can have negative effects on normal development resulting in embryonic death and caner. Therefore, the balance between active and repressed genes, epigenetically maintained by DNA methylation, is critical for normal development. Methylation of DNA has shown a huge impact in how organisms develop, especially in twin studies. Identical twins are genetically the same but are less likely to share the same phenotype as they develop and age. In infant
DNA makes up the genetic material for all organisms. However, not all organisms have distinct molecules working with DNA that come together to make up chromatin. Chromatin is only found in eukaryotic cells, the cellular makeup of multicellular organisms. The structure of chromatin is composed of DNA and histones, together making up nucleosomes, and other non-histone proteins that bind to the DNA. The backbone of DNA is negatively charged and histones have a positive charge allowing abundant interaction between the two molecules to organize and package multitudes of DNA at multiple levels, which must fit into an extremely tight space, in a way that allows gene regulation as well. Each of the pieces that make up chromatin structure …show more content…
This modification by DNA methyltransferase places a methyl group on the cytosine, one of the four nucleotide bases that make up the structure of DNA. Most of the time, methylation occurs on cytosines that are followed by a guanine known as CpG methylation. Since CpG sequences are concentrated upstream of genes in promoter regions of multicellular organisms, methylation of these sequences can effect gene expression greatly. When genes are active, CpG islands methylation levels are low, but when they are turned off, levels are high. Therefore DNA methylation is an inhibiting or gene silencing modification to chromatin structure. When DNA becomes methylated it attracts several proteins including MECP2 and MBD1 which recruits histone modifying enzymes to remove acetyl or add methyl modifications on histone tails. This allows the open chromatin to condense as nearby histones fold to block transcription from occurring. DNA methylation can interfere with recognition and binding of positively acting transcription factors also accounting for its inhibitory nature. There are three types of DNA methyltransferase (DNMT) enzymes that can be recruited when methylated histones bind chromodomain proteins. DNMT1 acts to improve DNA methylation maintenance and DNMT3A and DNMT3B acts to methylated unmethylated DNA. As with the histone modifying enzymes, studies show that deletion or mutated DNA modifying enzymes can have negative effects on normal development resulting in embryonic death and caner. Therefore, the balance between active and repressed genes, epigenetically maintained by DNA methylation, is critical for normal development. Methylation of DNA has shown a huge impact in how organisms develop, especially in twin studies. Identical twins are genetically the same but are less likely to share the same phenotype as they develop and age. In infant