| F'(prime) factor |
| A fertility factor into which a portion
of the bacterial chromosome has been incorporated. |
| F+(plus) cell |
| In Escherichia coli, a cell having a free
fertility factor; a male cell. |
| F-(minus) cell |
| In Escherichia coli, a cell having no fertility
factor; a female cell. |
| f-pili |
| Sex pili. Hair-like projections on an F+,
an F' or Hfr bacterium involved in anchorage during conjugation
and presumably through which DNA passes. |
| F1 generation |
| The first filial generation, produced by
crossing two parental lines. |
| F2 generation |
| The second filial generation, produced by
selfing or intercrossing the F1. |
| factorial |
| The product of all integers from the specified
number down to one (unity). |
| facultative heterochromatin
|
| Heterochromatin located in positions that
are composed of euchromatin in other individuals of the same species,
or even in the other homologue of a chromosome pair. |
| familial trait |
| A trait shared by members of a family. |
| family selection |
| A breeding technique of selecting a pair
on the basis of the average performance of their progeny. |
| Fanconi's anemia |
| An heritable disease in human beings with
a syndrome of congenital malformations (decreased blood cells, short
stature, patchy dark skin pimentation, predisposition to cancer
especially leukaemia) inherited as an autosomal recessive. |
| fate map |
| A map of an embryo showing areas that are
destined to develop into specific adult tissues and organs. A map
of the developmental fate of a zygote or early embryo showing the
adult organs that will develop from material at a given position
on the zygote or early embryo. |
| fecundity selection |
| The forces acting to cause one genotype
to be more fertile than another genotype. |
| feedback inhibition |
| A post-translational control mechanism in
which the end product of a biochemical pathway inhibits the activity
of the first enzyme of this pathway. |
| fertility factor (F factor)
|
| The plasmid that allows a prokaryote to
conjugate with and pass DNA into an F- cell. A bacterial episome
whose presence confers donor ability (maleness). |
| Filial generation |
| Offspring generation. F1 is the first offspring
or filial generation; F2 is the second; and so on. Successive generations
of progeny in a controlled series of crosses, starting with two
specific parents (the P generation) and selfing or intercrossing
the progeny of each new (F1; F2; . . . ) generation. |
| filter enrichment |
| A technique for recovering auxotrophic mutants
in filamentous fungi (in which non-auxotrophic organisms are filtered
off leaving a residue of non-growing auxotrophs). |
| fingerprint |
| 1. The characteristic spot pattern produced
by electrophoresis of the polypeptide fragments obtained through
denaturation of a particular protein with a proteolytic enzyme.
|
| 2. See DNA fingerprint. |
| first division segregation
(FDS) |
| The allele arrangement (4+4) of spores within
an ordered ascus that indicates the lack of recombination between
a locus and its centromere. A linear pattern (4+4) of spore phenotypes
within an ordered ascus for a particular allele pair, produced when
the alleles go into separate nuclei at the first meiotic division,
showing that no crossover has occurred between that allele pair
and the centromere. See Second division segregation. |
| fitness (W) |
| The relative reproductive success of a genotype
as measured by survival; fecundity or other life history parameters.
See Darwinian fitness and natural selection. |
| fixed allele |
| An allele for which all members of the population
under study are homozygous, so that no other alleles for this locus
exist in the population. |
| fixed breakage point
|
| According to the heteroduplex DNA recombination
model, the point from which unwinding of the DNA double helices
begins, as a prelude to formation of heteroduplex DNA. |
| fluctuation test |
| A test used in microbial genetics to establish
the random nature of mutation, or to measure mutation rates. An
experiment by Luria and Delbruck that compared the variance in number
of mutations among small cultures with subsamples of a large culture
to determine the mechanism of inherited change in bacteria. |
| focus map |
| A fate map of areas of the Drosophila blastoderm
destined to become specific adult structures, based on the frequencies
of specific kinds of mosaics. |
| Fokker-Planck equation
|
| An equation that describes diffusion processes.
It is used by population geneticists to describe random genetic
drift. |
| footprinting |
| A technique to determine the length of nucleic
acid in contact with a protein. While in contact the free DNA is
digested. The remaining DNA is then isolated and characterized.
|
| formylmethionine(fmet)
|
| A specialized amino acid that is the very
first one incorporated into the polypeptide chain in the synthesis
of proteins in Prokaryotes. |
| forward mutation |
| A mutation that converts a wild-type allele
to a mutant allele. See also reversion. |
| founder effect |
| Genetic drift observed in a population founded
by a small non representative sample of a larger population. |
| fragile site |
| A chromosomal region that has a tendency
to break. |
| fragile-X syndrome |
| The most common form of inherited mental
retardation. Named for its association with an X chromosome with
a tip that breaks or appears uncondensed. Inheritance involves imprinting.
|
| frameshift mutation |
| The insertion or deletion of a nucleotide
pair or pairs, causing a disruption of the translational reading
frame. |
| frameshift |
| A mutation in which there is an addition
or deletion of one, two or a small number (not a multiple of three)
of nucleotides that causes the codon reading frame to shift to one
of two others from the point of the mutation during translation.
Consequently the amino acid sequence of the protein is altered from
the point of the mutation to the carboxy terminus. |
| frequency histogram |
| A step curve in which the frequencies of
various arbitrarily bounded classes are graphed. |
| frequency-dependent fitness
|
| fitness differences whose intensity changes
with changes in the relative frequency of genotypes in the population.
|
| frequency-dependent selection
|
| Selection that involves frequency-dependent
fitness. Selection of a genotype depending on its frequency in the
population. |
| frequency-independent
selection |
| Selection in which the fitnesses of genotypes
are independent of their relative frequency in the population. |
| frequency-interdependent
fitness |
| fitness that is not dependent upon interactions
with other individuals of the same species. |
| fruiting body |
| In fungi, the organ in which meiosis occurs
and sexual spores are produced. |
| functional alleles |
| Mutants that fail to complement each other
in a cis-trans complementation test. |
| fundamental number |
| The number of chromosome arms in a somatic
cell of a particular species. |
