Related topics: genes · genetic variation · dna · dna sequences · chromosomes

Dark centers of chromosomes reveal ancient DNA

Geneticists exploring the dark heart of the human genome have discovered big chunks of Neanderthal and other ancient DNA. The results open new ways to study both how chromosomes behave during cell division and how they have ...

Tracking life's first step: Two molecules 'awaken' brand new genome

Within hours after fertilization, a unique genome forms from chromosomes contributed by the egg and sperm. However, this new genome is initially inactive and must be "awakened" to begin the transcription of its DNA and start ...

Virus genes help determine if pea aphids get their wings

Many of an organism's traits are influenced by cues from the organism's environment. These features are known as phenotypically plastic traits and are important in allowing an organism to cope with unpredictable environments.

Researchers identify the source of asymmetry in RNA-DNA hybrids

A study headed by the Institute for Research in Biomedicine (IRB Barcelona) and published in the journal CHEM furthers the understanding of the asymmetry between nucleic acid hybrids. This advance may make a significant contribution ...

DNA base editing induces substantial off-target RNA mutations

In a study published in Nature on June 10, researchers from Dr. Yang Hui's Lab at the Institute of Neuroscience of the Chinese Academy of Sciences (CAS), and collaborators from the CAS-MPG Partner Institute for Computational ...

Surprising enzymes found in giant ocean viruses

A new study led by researchers at Woods Hole Oceanographic Institution (WHOI) and Swansea University Medical School furthers our knowledge of viruses—in the sea and on land— and their potential to cause life-threatening ...

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Genome

In classical genetics, the genome of a diploid organism including eukarya refers to a full set of chromosomes or genes in a gamete; thereby, a regular somatic cell contains two full sets of genomes. In haploid organisms, including bacteria, archaea, viruses, and mitochondria, a cell contains only a single set of the genome, usually in a single circular or contiguous linear DNA (or RNA for retroviruses). In modern molecular biology the genome of an organism is its hereditary information encoded in DNA (or, for retroviruses, RNA).

The genome includes both the genes and the non-coding sequences of the DNA. The term was adapted in 1920 by Hans Winkler, Professor of Botany at the University of Hamburg, Germany. The Oxford English Dictionary suggests the name to be a portmanteau of the words gene and chromosome; however, many related -ome words already existed, such as biome and rhizome, forming a vocabulary into which genome fits systematically.

More precisely, the genome of an organism is a complete genetic sequence on one set of chromosomes; for example, one of the two sets that a diploid individual carries in every somatic cell. The term genome can be applied specifically to mean that stored on a complete set of nuclear DNA (i.e., the "nuclear genome") but can also be applied to that stored within organelles that contain their own DNA, as with the mitochondrial genome or the chloroplast genome. Additionally, the genome can comprise nonchromosomal genetic elements such as viruses, plasmids, and transposable elements. When people say that the genome of a sexually reproducing species has been "sequenced", typically they are referring to a determination of the sequences of one set of autosomes and one of each type of sex chromosome, which together represent both of the possible sexes. Even in species that exist in only one sex, what is described as "a genome sequence" may be a composite read from the chromosomes of various individuals. In general use, the phrase "genetic makeup" is sometimes used conversationally to mean the genome of a particular individual or organism. The study of the global properties of genomes of related organisms is usually referred to as genomics, which distinguishes it from genetics which generally studies the properties of single genes or groups of genes.

Both the number of base pairs and the number of genes vary widely from one species to another, and there is little connection between the two (an observation known as the C-value paradox). At present, the highest known number of genes is around 60,000, for the protozoan causing trichomoniasis (see List of sequenced eukaryotic genomes), almost three times as many as in the human genome.

An analogy to the human genome stored on DNA is that of instructions stored in a book:

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