The Epigenetics Revolution

Glossary

Autosomes The chromosomes which are not sex chromosomes. There are 22 pairs of autosomes in humans.

Blastocyst Very early mammalian embryo, consisting of about 100 cells. The blastocyst comprises a hollow ball of cells that will give rise to the placenta, surrounding a smaller, denser ball of cells that will give rise to the body of the embryo .

Chromatin DNA in combination with its associated proteins, especially histone proteins.

Concordance The degree to which two genetically identical individuals are identical phenotypically.

CpG A cytosine nucleotide followed by a guanine nucleotide in DNA. CpG motifs can undergo methylation on the C.

Discordance The degree to which two genetically identical individuals are non-identical phenotypically.

DNA replication Copying DNA to create new DNA molecules which are identical to the original.

DNMT DNA methyltransferase. An enzyme that can add methyl groups to cytosine bases in DNA.

Epigenome All the epigenetic modifications on the DNA genome and its associated histone proteins.

ES Cells Embryonic stem cells. Pluripotent cells experimentally derived from the Inner Cell Mass.

Exon Region of a gene that codes for a section that is present in the final version of the mRNA copied from that gene. Most, but not all, exons encode amino acids in the final protein produced from a gene.

Gamete An egg or a sperm.

Genome All the DNA in the nucleus of a cell.

Germline The cells that pass on genetic information from parent to child. These are the eggs and the sperm (and their precursors).

HDAC Histone deacetylase. An enzyme that can remove acetyl groups from histone proteins.

Histones Globular proteins that are closely associated with DNA, and which can be epigenetically modified.

Imprinting Phenomenon in which expression of certain genes depends on whether they were inherited from the mother or the father.

Inner Cell Mass (ICM) The pluripotent cells in the inside of the early blastocyst that will give rise to all the cells of the body.

Intron Region of a gene that codes for a section that is removed from the final version of the mRNA copied from that gene.

iPS Cells Induced pluripotent stem cells. Produced by reprogramming mature cells with specific genes that cause terminally differentiated cells to revert into pluripotent ones.

kb Kilobase. 1,000 base pairs.

miRNA Micro RNA. Small RNA molecules that are copied from DNA but that don’t code for proteins. miRNAs are a subset of ncRNAs

mRNA Messenger RNA. Copied from DNA and codes for proteins.

ncRNA Non-coding RNA. Copied from DNA and doesn’t code for proteins.

MZ Twins Monozygotic/ identical twins, formed when an early embryo splits in two.

Neurotransmitter A chemical produced by one brain cell that acts on another brain cell to alter its behaviour.

Nucleosome Combination of eight specific histone molecules with DNA wrapped around them.

Phenotype The observable characteristics or traits of an organism.

Pluripotency The ability of a cell to give rise to most other cell types. Typically, pluripotent mammalian cells give rise to all cells of the body, but not the cells of the placenta.

Priomordial germ cells Very specialised cells created in early development, which give rise ultimately to the gametes.

Promoter Region in front of a gene that controls how a gene is switched on.

Pronucleus The nucleus of a sperm or egg, following entry of a sperm into an egg, but before the two nuclei fuse.

Retrotransposons Unusual segments of DNA that don’t code for protein and can move between different locations in the genome. Believed to have originated from viruses.

RNA Single stranded copy of a specific region of DNA. The term RNA stands for ribonucleic acid. It includes various different classes of RNA molecules including miRNA, mRNA and ncRNA.

Sex chromosomes The X and Y chromosomes that govern sex determination in mammals. Normally, females have two X chromosomes and males have one X and one Y chromosome.

Somatic cells Cells of the body.

Somatic Cell Nuclear Transfer (SCNT) The transfer of the nucleus from a mature cell into another cell, usually an egg.

Somatic mutations Mutations that happen in the cells of the body, rather than ones that have been inherited via sperm or eggs.

Stochastic variation A random change or fluctuation.

Totipotency The ability of a cell to give rise to all cells of the body and the placenta.

Transcription Copying DNA to create RNA molecules.

Transgenerational inheritance The phenomenon in which phenotypic changes in one generation are passed on to the next, without any alteration in the genetic code.

Uniparental disomy A situation where both members of a pair of chromosomes have been inherited from one parent, rather than one from each parent. For example, maternal uniparental disomy of chromosome 11 would mean both copies of chromosome 11 had come from the mother.

Vernalisation The process where plants need a period of cold before they will flower.

Zygote The totipotent cell formed when an egg and a sperm fuse.