InvertebrateInvertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a backbone or spine), derived from the notochord. This is a grouping including all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelids, echinoderms and cnidarians. The majority of animal species are invertebrates; one estimate puts the figure at 97%. Many invertebrate taxa have a greater number and variety of species than the entire subphylum of Vertebrata.
HomeoboxA homeobox is a DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development. Mutations in a homeobox may change large-scale anatomical features of the full-grown organism. Homeoboxes are found within genes that are involved in the regulation of patterns of anatomical development (morphogenesis) in animals, fungi, plants, and numerous single cell eukaryotes.
Homeotic geneHomeotic genes are genes which regulate the development of anatomical structures in various organisms such as echinoderms, insects, mammals, and plants. Homeotic genes often encode transcription factor proteins, and these proteins affect development by regulating downstream gene networks involved in body patterning. Mutations in homeotic genes cause displaced body parts (homeosis), such as antennae growing at the posterior of the fly instead of at the head. Mutations that lead to development of ectopic structures are usually lethal.
Insulator (genetics)An insulator is a type of cis-regulatory element known as a long-range regulatory element. Found in multicellular eukaryotes and working over distances from the promoter element of the target gene, an insulator is typically 300 bp to 2000 bp in length. Insulators contain clustered binding sites for sequence specific DNA-binding proteins and mediate intra- and inter-chromosomal interactions. Insulators function either as an enhancer-blocker or a barrier, or both.
GenomeIn the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as regulatory sequences (see non-coding DNA), and often a substantial fraction of junk DNA with no evident function. Almost all eukaryotes have mitochondria and a small mitochondrial genome.
Genome sizeGenome size is the total amount of DNA contained within one copy of a single complete genome. It is typically measured in terms of mass in picograms (trillionths (10−12) of a gram, abbreviated pg) or less frequently in daltons, or as the total number of nucleotide base pairs, usually in megabases (millions of base pairs, abbreviated Mb or Mbp). One picogram is equal to 978 megabases. In diploid organisms, genome size is often used interchangeably with the term C-value.
OviparityOviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most animals. Modes of reproduction The traditional modes of reproduction include oviparity, taken to be the ancestral condition, traditionally where either unfertilised oocytes or fertilised eggs are spawned, and viviparity traditionally including any mechanism where young are born live, or where the development of the young is supported by either parent in or on any part of their body.
Divergent evolutionDivergent evolution or divergent selection is the accumulation of differences between closely related populations within a species, sometimes leading to speciation. Divergent evolution is typically exhibited when two populations become separated by a geographic barrier (such as in allopatric or peripatric speciation) and experience different selective pressures that drive adaptations to their new environment. After many generations and continual evolution, the populations become less able to interbreed with one another.
Human genomeThe human genome is a complete set of nucleic acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule found within individual mitochondria. These are usually treated separately as the nuclear genome and the mitochondrial genome. Human genomes include both protein-coding DNA sequences and various types of DNA that does not encode proteins. The latter is a diverse category that includes DNA coding for non-translated RNA, such as that for ribosomal RNA, transfer RNA, ribozymes, small nuclear RNAs, and several types of regulatory RNAs.
Genome evolutionGenome evolution is the process by which a genome changes in structure (sequence) or size over time. The study of genome evolution involves multiple fields such as structural analysis of the genome, the study of genomic parasites, gene and ancient genome duplications, polyploidy, and comparative genomics. Genome evolution is a constantly changing and evolving field due to the steadily growing number of sequenced genomes, both prokaryotic and eukaryotic, available to the scientific community and the public at large.
