FORM 7 BIOLOGY
GLOSSARY FOR BIOTECHNOLOGY
A RECOMBINANT DNA TECHNOLOGY - also called genetic engineering,
gene splicing, genetic modification.
1. RESTRICTION ENZYMES & LIGATION
Restriction enzyme - one of group of bacterial enzymes - endonucleases
- that cut DNA into short sequences. Each restriction enzyme
has its own specific recognition site. “Molecular scalpels”.
Recognition Site - specific place in the DNA sequence where a restriction enzyme
Sticky end - cut end of a DNA sequence with unpaired bases (exposed
Blunt end - an end of double stranded DNA fragment (cut by a restriction
enzyme) in which neither strand protrudes past the end of the
Plasmid - extra-chromosomal (ie. extra to the main loop chromosome)
circular DNA molecule found in some bacteria. May carry 2-3
genes or many genes.
Ligation - sticking together, joining, tying, or, specifically, “covalently
joining together 2 ends of nucleic acids.
DNA Ligase - an enzyme that stimulates the base-pairing of sticky ends.
Endonuclease - an enzyme that cuts DNA at a specific site within the DNA
Exonuclease - an enzyme that degrades DNA from the end of the molecule.
2. REVERSE TRANSCRIPTION
Reverse Transcription - the process of copying an RNA template onto complementary
DNA (cDNA) using the enzyme reverse transcriptase.
cDNA - complementary DNA DNA synthesised from (and so
complementary to) an RNA template (so it CONTAINS EXONS
Intron - long non-coding regions in the genome (“interruptions”).
Exon - sequence on a chromosome (DNA molecule) that codes for a
Artificial Gene - found on cDNA - exons only.
cDNA Library - Library is a large collection of clones made with a sample of
genomic DNA from the organism of interest - can be then
recorded on cDNA.
3. POLYMERASE CHAIN REACTION - PCR
PCR - an enzymatic method for amplifying a specific segment of DNA.
Amplification - increasing the number of copies of a specific DNA molecule.
Linear PCR - PCR where the same original DNA templates are used over and
over (rather than the PCR products).
Taq DNA Polymerase -Polymerase that works at high temperatures ( from thermophile
Primers - Short DNA strands that provide a starting sequence for DNA
replication (oligonucleotide that anneals to its complementary
section thus forming a short double stranded region). About 20
Anneal - the hybridisation of a single stranded DNA molecule to another
single stranded DNA molecule of complementary sequence.
Oligonucleotides - several nucleotides joined together to form a short single -
stranded DNA molecule about 100 bases long. Scientists can now
synthesize any sequence they want.
- the growing of the new bit of DNA from the primer 31 end. The
enzymatic extension of the oligonucleotide template hybrid
incorporating nucleotides complementary to the template.
4. DNA SEQUENCING
DNA Sequencing - technique used to determine the base sequence of DNA.
Dideoxynucleotide - modified nucleotide, missing a crucial oxygen atom. These
effectively terminate DNA synthesis when incorporated into a
normally growing strand. (You can get four kinds - A, C G, t )
Radio-labelled Primer - Primer sequence containing a radioactive isotope that will show
up on a photographic film.
5. DNA FINGERPRINTING
DNA Fingerprint - pattern on an X-ray film; light and dark bands (dark bands,
Mini satellites - repeating sequence of bases in DNA, no known function. Occur
in “alleles” just like functional genes. Different individuals have
different numbers of repeats so it can be an identification feature.
Electrophoresis - technique for separating DNA fragments based on their different
mobility in an electric field (small ones move further).
Genetic Probe - synthetic piece of DNA, made to order in the lab, radioactive
labels attached. Bind to complementary minisatellite sequence
RFLPs -Restriction Fragment Length Polymorphisms. Fragments from the
non-coding areas of the homologous chromosomes. Can be used as
genetic markers and are inherited in a Mendelian way.
Multilocus Probes - a short length of radioactive, double-stranded DNA. Many of
these bind onto tested DNA in many places and produce a DNA
fingerprint with many bands for comparison.
Singlelocus Probes - Copies of a single long length of DNA bind to the tested DNA at
only one point. Produces only 1 (homozygous) or 2
Complementary Sequence - sequence that will hybridise with a specified sequence. Nucleic
acid strands run antiparallel and base-pair, so the complement of
51 A G G T C - 31 is 51 G A G C T- 31
Southern Blotting - process that allows a mapper to define the position of specific
DNA sequences in the electrophoresis gel.
Southern Blot - DNA that has been electrophoretically separated and
immobilised (on nitrocellulose).
6. GENE CLONING USING A VECTOR
Vector - (carrying agent) Self-replicating DNA molecule (eg. plasmid or
viral DNA) used to transmit a gene from one organism to another.
Bacteriophage - viruses that infect bacteria. Useful as vectors.
Plasmid - extra- chromosomal circular DNA molecule found in some
bacteria. May carry 2-3 genes or many genes.
Transformation - the insertion of newly engineered sequences of DNA into live
Gene cloning - the process of making large quantities of DNA.
Recombinant DNA - a DNA molecule that contains combined genetic material from
Cosmid - a modified plasmid containing sequences from bacteriophage
that allow the insertion of large DNA fragments. Cosmids are
circular double-stranded molecules, typically 45-48kb long
including the vector sequences.
Transgenesis - the process of making a transgenic organism that has a piece of
foreign DNA, usually a gene, artificially and stably inserted into
its own DNA and germ line.
- movement of genes from one species to another.
Transformation - the introduction of DNA into an organism so that the DNA can
be inherited by subsequent generations.
Gene therapy - transformed animal cells provide a means of curing genetic
defects in humans. Viral vectors and liposomes are used.
B PLANT TISSUE CULTURE
8. PLANT TISSUE CULTURE
Micropropogation - plant tissue culture.
Cloning - process whereby many genetically identical individuals are made
from the same cell line.
Transgenic Organisms - organisms that have received DNA from another source.
Explant - small piece cut or excised from the plant.
Callus - undifferentiated mass of cells which has developed from the
Protoplasts - “naked” plant cells that have had their cell walls artificially
removed by bacterial and fungal enzymes.
Somaclonal variation - variation that occurs despite the fact that protoplasts are cloned
from one line of somatic cells (in other words, shouldn’t happen!)
Cybrids - hybrids in which the cytoplasm of two species is mixed without
the mixing of the nuclear genes.
In vitro - when a natural process is carried on outside the living organism
“in glass” - test tube or petri dish.
In vivo - the natural process is allowed to happen inside the living organism.
Meristem - plant tissue capable of reproduction (mitosis).