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A DNA and protein complex that is found in the nuclei of eukaryotic cells and stores most of the genetic information for a species. Chromatin was first discovered and named by German biologist Walther Flemming in 1879. While staining cells…

A long noncoding ribonucleic acid, specific to the female inactive X chromosome, that orchestrates X-chromosome inactivation in eutherian mammals. The X-inactive specific transcript, Xist (Fig. 1), is essential for inactivation of the X chromosome…

Either member of a pair of chromosomes responsible for sex determination of an organism. The genome of every mammal consists of the autosomal (non-sex) chromosomes (or autosomes), of which all individuals normally carry two copies, and the…

The study of the hereditary factors that shape behavior. Behavior genetics, that is, the scientific investigation of the hereditary factors that influence behavior, may be studied in animals and humans. Charles Darwin, who originated the theory that…

Each copy of the human genome is made up of just over 3.2 billion pairs of nucleotides (the structural units of nucleic acids), comprising the individual “letters” that make up all deoxyribonucleic acid (DNA) sequences. The sequence is…

Any of the elementary infectious agents that possess some of the properties of living systems, such as having a genome and being able to adapt to changing environments. Viruses comprise a large group of infectious agents ranging from 10 to 400…

The series of visible changes that occur in the nucleus and chromosomes of non-gamete-producing plant and animal cells as they divide. During mitosis, the replicated genes, packaged within the nucleus as chromosomes, are precisely…

Sex chromosomes have evolved from an ordinary pair of autosomes (non-sex chromosomes) in multiple lineages, including flies, worms, and mammals. Lack of recombination between the sex chromosomes has led to loss and differentiation of genes…

The Nobel Prizes for 2020 included the following awards for scientific disciplines. Chemistry The chemistry prize was awarded jointly to Emmanuelle Charpentier of the Max Planck Unit for the Science of Pathogens, Berlin, Germany; and Jennifer A.…