Chromatin remodelingChromatin remodeling is the dynamic modification of chromatin architecture to allow access of condensed genomic DNA to the regulatory transcription machinery proteins, and thereby control gene expression. Such remodeling is principally carried out by 1) covalent histone modifications by specific enzymes, e.g., histone acetyltransferases (HATs), deacetylases, methyltransferases, and kinases, and 2) ATP-dependent chromatin remodeling complexes which either move, eject or restructure nucleosomes.
5-Hydroxymethylcytosine5-Hydroxymethylcytosine (5hmC) is a DNA pyrimidine nitrogen base derived from cytosine. It is potentially important in epigenetics, because the hydroxymethyl group on the cytosine can possibly switch a gene on and off. It was first seen in bacteriophages in 1952. However, in 2009 it was found to be abundant in human and mouse brains, as well as in embryonic stem cells. In mammals, it can be generated by oxidation of 5-methylcytosine, a reaction mediated by TET enzymes. Its molecular formula is C5H7N3O2.
Transgenerational epigenetic inheritanceTransgenerational epigenetic inheritance is the transmission of epigenetic markers and modifications from one generation to multiple subsequent generations without altering the primary structure of DNA. Thus, the regulation of genes via epigenetic mechanisms can be heritable; the amount of transcripts and proteins produced can be altered by inherited epigenetic changes. In order for epigenetic marks to be heritable, however, they must occur in the gametes in animals, but since plants lack a definitive germline and can propagate, epigenetic marks in any tissue can be heritable.
CpG siteThe CpG sites or CG sites are regions of DNA where a cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5' → 3' direction. CpG sites occur with high frequency in genomic regions called CpG islands (or CG islands). Cytosines in CpG dinucleotides can be methylated to form 5-methylcytosines. Enzymes that add a methyl group are called DNA methyltransferases. In mammals, 70% to 80% of CpG cytosines are methylated.
Angelman syndromeAngelman syndrome or Angelman's syndrome (AS) is a genetic disorder that mainly affects the nervous system. Symptoms include a small head and a specific facial appearance, severe intellectual disability, developmental disability, limited to no functional speech, balance and movement problems, seizures, and sleep problems. Children usually have a happy personality and have a particular interest in water. The symptoms generally become noticeable by one year of age.
Extended evolutionary synthesisThe extended evolutionary synthesis consists of a set of theoretical concepts argued to be more comprehensive than the earlier modern synthesis of evolutionary biology that took place between 1918 and 1942. The extended evolutionary synthesis was called for in the 1950s by C. H. Waddington, argued for on the basis of punctuated equilibrium by Stephen Jay Gould and Niles Eldredge in the 1980s, and was reconceptualized in 2007 by Massimo Pigliucci and Gerd B. Müller. Notably, Dr.
5-Methylcytosine5-Methylcytosine is a methylated form of the DNA base cytosine (C) that regulates gene transcription and takes several other biological roles. When cytosine is methylated, the DNA maintains the same sequence, but the expression of methylated genes can be altered (the study of this is part of the field of epigenetics). 5-Methylcytosine is incorporated in the nucleoside 5-methylcytidine. In 5-methylcytosine, a methyl group is attached to the 5th atom in the 6-atom ring, counting counterclockwise from the NH-bonded nitrogen at the six o'clock position.
Bisulfite sequencingBisulfite sequencing (also known as bisulphite sequencing) is the use of bisulfite treatment of DNA before routine sequencing to determine the pattern of methylation. DNA methylation was the first discovered epigenetic mark, and remains the most studied. In animals it predominantly involves the addition of a methyl group to the carbon-5 position of cytosine residues of the dinucleotide CpG, and is implicated in repression of transcriptional activity.
Origin of replicationThe origin of replication (also called the replication origin) is a particular sequence in a genome at which replication is initiated. Propagation of the genetic material between generations requires timely and accurate duplication of DNA by semiconservative replication prior to cell division to ensure each daughter cell receives the full complement of chromosomes. This can either involve the replication of DNA in living organisms such as prokaryotes and eukaryotes, or that of DNA or RNA in viruses, such as double-stranded RNA viruses.
Somatic (biology)In cellular biology, the term somatic is derived from the French somatique which comes from Ancient Greek σωματικός (sōmatikós, “bodily”), and σῶμα (sôma, “body”.) is often used to refer to the cells of the body, in contrast to the reproductive (germline) cells, which usually give rise to the egg or sperm (or other gametes in other organisms). These somatic cells are diploid, containing two copies of each chromosome, whereas germ cells are haploid, as they only contain one copy of each chromosome (in preparation for fertilisation).
