| V-J joining |
| The joining of a variable (V) gene segment
and a joining (J) gene segment in the first step of the formation
of a functioning immunoglobulin gene. |
| Val |
| Valine (an amino acid). |
| variable |
| A property that may have different values
in various cases. |
| variable region |
| A region in an immunoglobin molecule that
shows many sequence differences between antibodies of different
specificities; the part of the antibody that binds to the antigen.
See immunoglobulin gene. |
| variable-number-of-tandem-repeats
(VNTR) locus |
| locus that is hypervariable because of tandemly
repeated DNA sequences. Presumably variability is generated by unequal
crossing over or slippage during replication. A chromosomal locus
at which a particular repetitive sequence is present in different
numbers in different individuals of a population or in the two different
chromosome homologues in one diploid individual. |
| variance |
| The average squared deviation about the
mean of a set of data. A measure of the variation around the central
class of a distribution; the average squared deviation of the observations
from their mean value. |
| variant |
| An individual organism that is recognizably
different from an arbitrary standard type in that species. |
| variate |
| A specific numerical value of a variable.
|
| variation |
| The differences among parents and their
offspring or among individuals in a population. |
| variegation |
| The occurrence within a tissue of sectors
or clones with differing phenotypes. Patchiness; a type of position
effect that results when particular loci are contiguous with heterochromatin.
See position-effect variegation. |
| vector |
| In DNA cloning, the plasmid or phage chromosome
used to carry the cloned DNA segment. |
| viability |
| The probability that a fertilized egg will
survive and develop into an adult organism. |
| virion |
| A virus particle. |
| viroid |
| RNA molecule that is a plant pathogen. |
| virulent phage |
| A phage that cannot become a prophage; infection
by such a phage always leads to lysis of the host cell. |
| virus |
| A particle consisting of a nucleic acid
(RNA or DNA) genome surrounded by a protein coat (capsid) and sometimes
also a membrane, which can replicate only after infecting a host
cell. A virus particle may exist free of its host cell but is incapable
of replicating on its own. |
