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 will “snip”.

Sticky end - cut end of a DNA sequence with unpaired bases (exposed nucleotide bases).

Blunt end - an end of double stranded DNA fragment (cut by a restriction enzyme) in which neither strand protrudes past the end of the other.

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 molecule.

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

ONLY).

Intron - long non-coding regions in the genome (“interruptions”).

Exon - sequence on a chromosome (DNA molecule) that codes for a final protein.

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 bacteria.)

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 bases long.

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.

Primer Extension - 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, more DNA.

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 for identification.

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.

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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 (heterozygous) bands.

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 bacteria.

Gene cloning - the process of making large quantities of DNA.

Recombinant DNA - a DNA molecule that contains combined genetic material from two sources.

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.

7. TRANSGENESIS

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.

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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 explant.

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).

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