Facultative heterochromatin
Chromatin that may become condensed and therefore transcriptionally inactive in certain cell types, at different developmental stages, or in one member of a homologous chromosome pair.
Familial trait
A characteristic shared by members of a family as the result of shared genes and/or environmental factors.
Fate map
A diagram of an early embryo showing the cell types and tissues that different embryonic cells subsequently develop into.
F-duction
Transfer of host genes carried on an f factor in conjugation between an f and an f–cell. If the genes are different between the two cell types, the recipient becomes partially diploid for the genes on the f.
F factor
In e. Coli, a plasmid—a self-replicating circular DNA molecule—that confers the ability to act as a donor cell in conjugation. Excision of an f factor from the bacterial chromosome may generate an f¿ factor, which may carry host cell genes.
F1 generation
The offspring that result from the first experimental crossing of two parental strains of animals or plants; the first filial generation.
F2 generation
The offspring that result from crossing f1 individuals; the second filial generation. Fine-structure mapping procedures for generating a high resolution map of allele sites within a gene.
Formylmethionine (fmet)
A modified form of the amino acid methionine that has a formyl group attached to the amino group. It is the first amino acid incorporated into a polypeptide chain in prokaryotes and in eukaryotic organelles.
Forward mutation
A point mutation in a wild-type allele that changes it to a mutant allele.
Founder effect
A form of genetic drift that occurs when a population is formed by migration of a small number of individuals from a large population.
F-pili (singular, f-pilus)
Hairlike cell surface components produced by cells containing the f factor, which allow the physical union of f+ and f–cells or hfr and f–cells to take place. Also called sex pili.
Frameshift mutation
A mutational addition or deletion of a base pair in a gene that disrupts the normal reading frame of the corresponding mRNA.
Frequency distribution
In genetics, a graphical representation of the numbers of individuals within a population who fall within the same range of phenotypic values for a continuous quantitative trait. Typically, the phenotypic classes are plotted on the horizontal axis and the number of individuals in each class are plotted on the vertical axis.
Functional genomics
The comprehensive analysis of the functions of genes and of non gene sequences in entire genomes, including patterns of gene expression and its control.
