Glossary Plant Breeding

Restoration. Mitigating the effects induced by any physical or chemical agent to a
biological system. The terms like recovery, reactivation are frequently used as
synonyms for restoration.
Restorer Gene. A gene that brings back the changes brought about by the cytoplasmic
male sterility.
Restorer Line. A line which restores pollen-producing ability in the hybrid after crossing
with A line by providing a copy of restorer gene; also called R line.
Restriction Endonucleases. Enzymes that recognise and cut specific nucleotide
sequences in DNA. Type II restriction endonucleases are used in the construction of
recombinant DNA molecules. These enzymes provide powerful tool for analysis of
DNA organization, gene structure and gene regulation.
Restriction Enzyme. An endonuclease that recognises specific target nucleotide
sequences in DNA and breaks the DNA chain at those points. A variety of such
enzymes is now known, and is used extensively in genetic engineering.
Restriction Fragment Length Polymorphism (RFLP). Variations occurring within a
species in the length of DNA fragments generated by a specific endonuclease. RFLPs
are useful as molecular markers.
Restriction Fragment. A fragment of DNA created by cleavage at specific sites by a
restriction endonuclease.
Restriction Map. A map of a chromosomal region showing the positions of target sites
of one or more restriction enzymes.
Restrictive Conditions. Environmental conditions under which a conditional mutant
shows the mutant phenotype.
Retrotransposon. A transposable element that utilises reverse transcriptase to transpose
through an RNA intermediate.
Retrovirus. An RNA virus that replicates by first being converted into double-stranded
DNA.
Reverse Genetics. The study of genetics that begins with a segment of DNA (genotype)
or a protein sequence to investigate its function (phenotype). It also determines how a
mutation at a particular site in a gene affects the phenotype. It is so called as it directly
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