Transcription coregulatorIn molecular biology and genetics, transcription coregulators are proteins that interact with transcription factors to either activate or repress the transcription of specific genes. Transcription coregulators that activate gene transcription are referred to as coactivators while those that repress are known as corepressors. The mechanism of action of transcription coregulators is to modify chromatin structure and thereby make the associated DNA more or less accessible to transcription.
Genome instabilityGenome instability (also genetic instability or genomic instability) refers to a high frequency of mutations within the genome of a cellular lineage. These mutations can include changes in nucleic acid sequences, chromosomal rearrangements or aneuploidy. Genome instability does occur in bacteria. In multicellular organisms genome instability is central to carcinogenesis, and in humans it is also a factor in some neurodegenerative diseases such as amyotrophic lateral sclerosis or the neuromuscular disease myotonic dystrophy.
Non-Mendelian inheritanceNon-Mendelian inheritance is any pattern in which traits do not segregate in accordance with Mendel's laws. These laws describe the inheritance of traits linked to single genes on chromosomes in the nucleus. In Mendelian inheritance, each parent contributes one of two possible alleles for a trait. If the genotypes of both parents in a genetic cross are known, Mendel's laws can be used to determine the distribution of phenotypes expected for the population of offspring.
Developmental stage theoriesIn psychology, developmental stage theories are theories that divide psychological development into distinct stages which are characterized by qualitative differences in behavior. There are several different views about psychological and physical development and how they proceed throughout the life span. The two main psychological developmental theories include continuous and discontinuous development. In addition to individual differences in development, developmental psychologists generally agree that development occurs in an orderly way and in different areas simultaneously.
Gap geneA gap gene is a type of gene involved in the development of the segmented embryos of some arthropods. Gap genes are defined by the effect of a mutation in that gene, which causes the loss of contiguous body segments, resembling a gap in the normal body plan. Each gap gene, therefore, is necessary for the development of a section of the organism. Gap genes were first described by Christiane Nüsslein-Volhard and Eric Wieschaus in 1980. They used a genetic screen to identify genes required for embryonic development in the fruit fly Drosophila melanogaster.
Progeroid syndromesProgeroid syndromes (PS) are a group of rare genetic disorders that mimic physiological aging, making affected individuals appear to be older than they are. The term progeroid syndrome does not necessarily imply progeria (Hutchinson–Gilford progeria syndrome), which is a specific type of progeroid syndrome. Progeroid means "resembling premature aging," a definition that can apply to a broad range of diseases. Familial Alzheimer's disease and familial Parkinson's disease are two well-known accelerated-aging diseases that are more frequent in older individuals.
CondensinCondensins are large protein complexes that play a central role in chromosome assembly and segregation during mitosis and meiosis (Figure 1). Their subunits were originally identified as major components of mitotic chromosomes assembled in Xenopus egg extracts. Many eukaryotic cells possess two different types of condensin complexes, known as condensin I and condensin II, each of which is composed of five subunits (Figure 2).
Chromosomal rearrangementIn genetics, a chromosomal rearrangement is a mutation that is a type of chromosome abnormality involving a change in the structure of the native chromosome. Such changes may involve several different classes of events, like deletions, duplications, inversions, and translocations. Usually, these events are caused by a breakage in the DNA double helices at two different locations, followed by a rejoining of the broken ends to produce a new chromosomal arrangement of genes, different from the gene order of the chromosomes before they were broken.
