Key Words - Module 6

Allele

A version of a gene

Allopatric speciation

Speciation that occurs when two populations are geographically isolated due to a physical barrier

Apoptosis

Programmed cell death

Autosomal linkage

When two or more genes are positioned on the same autosome. Unlikely to be separated by crossing over so often inherited together

Autosome

Chromosome that is not an X or Y chromosome

Bioinformatics

Development of computer tools and software required to organise and analyse unprocessed biological data

Chi-squared

Statistical test used to determine whether a pattern of inheritance is significant

Chlorosis

Condition on which plant leaf cells produce insufficient chlorophyll, resulting in pale or yellow coloured leaves. This may be due to mineral deficiencies, lack of light or viral infections

Codominance

When both alleles for a gene in a heterozygous organism equally contribute to the phenotype

Computational biology

The use of computational techniques to analyse large amounts of biodata and build theoretical models of biological systems

Continuous variation

A type of variation that cannot be categorised. Produces a continuous range in which characteristics can take any value

Deletion

Gene mutations in which one or more nucleotide bases are removed from a DNA sequence. May lead to a frameshift mutation, changing every successive codon

Dihybrid inheritance

The determination of a trait by the inheritance of two genes

Directional selection

A type of selection that favours one extreme phenotype and selects against all other phenotypes

Discontinuous variation

Variation that can be categorised. A characteristic can only appear in discrete values, influenced by one of two genes

Disruptive selection

Type of selection that favours individuals with extreme phenotypes and selects against those with phenotypes close to the mean

DNA barcode

Short sequence of DNA that is used to identify a species

DNA ligase

An enzyme that joins the sugar-phosphate backbone of two DNA segments

DNA profiling

Technique used to determine the patterns in the non-coding DNA of an individual. It involves the five main stages: extraction, digestion, separation, hybridisation, and observation

DNA sequencing

Determining the entire DNA nucleotide base sequence of an organism

Dominant

Allele that is always expressed

Electrophoresis

Chromatography that separates nucleic acid fragments or proteins by size using electric current

Electroporation

Method of transformation in which a small electric current is used to transfer recombinant plasmids into bacterial cells to fragments of DNA into eukaryotic cells

Epistasis

Describes a relationship between genes at different loci, where the allele of one gene affects the expression of a different gene

Etiolation

Condition in plants characterised by weak stems and small, pale leaves, due to insufficient exposure to light

Evolution

The gradual change in the allele frequencies within a population over time. Occurs due to natural selection

Exon

A sequence of DNA that codes for an amino acid sequence

Founder effect

A type of genetic drift in which a few individuals of a species break off from the population and form a new colony. This results in smaller gene pools and an increased frequency of rare alleles

Gene mutation

A change to at least one nucleotide base in DNA or the arrangement of bases. Gene mutations can occur spontaneously during DNA replication and may be beneficial, damaging, or neutral

Gene therapy

A therapeutic technique in which a faulty allele is replaced with a functional allele in order to treat or prevent disease

Genetically modified organism

Organism that has had its genome altered

Genetic bottleneck

A drastic reduction in population size leading to reduced genetic diversity within a population

Genetic drift

Random variations in allele frequencies in small populations due to mutations

Genetic engineering

Modification of the genome of an organism by the insertion of a desired gene from another organism. This enables the formation of organisms with beneficial characteristics

Genome

Complete genetic material of an organism

Genotype

An organisms genetic composition

Germ line cell gene therapy

A type of gene therapy in which a faulty allele is replaced with a functional allele in germ cells or a very early embryo. The effects are permanent and can be inherited

Hardy-Weinberg principal

A model that predicts the ratio of dominant and recessive alleles in a population will remain constant between generations is the following five conditions are met: no new mutations; no natural selection; no migration; large population; and random mating.

Heterozygous

When someone has two different alleles of a gene

High-throughput sequencing

Large scale approaches to DNA sequencing that use a flow cell. Enable many clusters of DNA fragments to be sequenced simultaneously, giving efficient and rapid sequencing

Homeobox genes

A group of regulatory genes that contain and homeobox, a DNA sequence that is highly conserved in animals, plants and fungi. Homeobox genes are responsible for the development of body plans in different organisms

Homozygous

When someone has two identical alleles of a gene

Hox gene

A type of homeobox gene that is present in animals only

Inbreeding

Formation of offspring from the breeding of closely related individuals

Insertion

A form of gene mutation in which one or more nucleotide bases are added to a DNA sequence. May lead to a frameshift mutation

Intron

Non-coding sequence of DNA

Lac operon

Group of three structural genes, lacZ, lacY, and lacA that are required for the metabolism of lactose

Mature mRNA

Final mRNa product that has had introns removed as well as having undergone other post-transcriptional changes

Mitosis

Cell division that produces two genetically identical diploid daughter cells.

Monogenic inheritance

Determination of a trait by the inheritance of a single gene

Multiple alleles

When a gene has more that two potential alleles

Mutagen

A chemical, biological, or physical agent that increases the rate of gene mutant ions above normal level

Operon

A group of genes that are expressed together and controlled by the same regulatory mechanism

Phenotype

Organisms observable characteristics. Due to interactions of the genotype and environment

Polymerase Chain Reaction (PCR)

An in vitro technique used to rapidly amplify fragments of DNA

Post-transcriptional control

The level of gene regulation in which primary mRNA can be modified, controlling translation

Post-translational control

The level of gene regulation in which proteins can be modified post-synthesis

Pre-mRNA

The product of transcription before any post-transcriptional regulation

Recessive

Describes and allele that is only expressed in the absence of a dominant allele

Recombinant DNA

DNA that has had fragments of foreign DNA inserted

Regulatory gene

Gene that codes for the production of proteins involves in DNA regulation. Influenced by internal and external stimuli

Repressor protein

Protein that binds to the operator, altering the transcription rate

Restriction endonucleases

Enzymes that cut DNA molecules at recognition sequences creating sticky ends

Sanger sequencing

First method of DNA sequencing that involved formation of DNA fragments of varying lengths. Fluorescent ‘terminator’ bases marked the final base of each fragment, allowing over DNA sequence to be determined

Selection pressures

Factors that affect an organisms ability to survive in an environment

Selective breeding

Humans artificially select organisms with desirable characteristics and breed them to produce offspring with desirable phenotypes

Sex-linkage

Presence of a gene on an X or Y chromosome

Sexual reproduction

A form of reproduction involving the random fusion of male and female gametes

Somatic cell gene therapy

A type of gene therapy in which a faulty allele is replaced with a functional allele in affected somatic cells. Effects are temporary and cannot be inherited

Speciation

Formation of a new species due to the evolution of two reproductively separated populations. Two types allopatric and sympatric

Stabilising selection

Type of selection that favours individuals with phenotypes close to the mean and selects against extreme phenotypes

Sticky ends

The staggered cut formed by restriction endonucleases in double-stranded DNA

Structural gene

Gene that codes for the production of proteins or enzymes that are not involved in DNA regulation

Substitution

A form of gene mutation in which one nucleotide base is exchanged for another. This may change an amino acid if produce the same amino acid

Sympatric speciation

A form of speciation that occurs when two populations within the same area become reproductively isolated

Synthetic biology

The design and construction of new biological entities, as well as the reconstruction of pre-existing natural biological systems

Thermocycler

A machine controlled by a computer that varies temperatures at predetermined time intervals

Transcriptional control

Level of gene regulation in which genes are switched ‘on’ or ‘off’

Transcription factors

Proteins that help switch genes ‘on’ or ‘off’

Transgenic organism

An organism that contains recombinant DNA

Translational control

Level of gene regulation in which translation can be initiated or stopped

Vector

Carrier used to transfer a gene from one organism to another

Artificial twinning

Artificial production of monozygotic twins from the manual splitting of the early embryo

Aseptic techniques

Techniques used to culture microorganisms under sterile conditions in order to minimise contamination

Batch fermentation

Industrial method of fermentation that runs for a set period of time. Culture broth is not removed until the fermentation is complete

Bioremediation

Use of microorganisms to remove soil and water pollution

Biotechnology

Field of biology involving the use of living systems to produce or transform materials

Brewing

Production of beer from the steeping of barley in water, and fermentation of the resulting product with yeast

Clones

Genetically identical offspring produced as a result of cloning

Cloning

Method of producing genetically identical offspring by asexual reproduction

Continuous fermentation

Industrial method in which culture broth is continuously removed and extra nutrient medium is added. Conditions remain relatively constant

Culture

The growth of living matter in vitro in suitable conditions

Cutting

Small section of the root or stem of an adult plant used in horticulture to produce natural clones

Enucleation

Removal of the nucleus

Fermentation

Anaerobic respiration that does not involve an electron transport chain

Immobilised aminoacylase

An immobilised enzyme that is used to produce pure samples of L-amino acids

Immobilised enzymes

Enzymes which are attached to inert, insoluble material over which the substrate passes and the reaction takes place

Immobilised glucoamylase

An immobilised enzyme that can be used to breakdown dextrins into glucose

Immobilised glucose isomerase

An immobilised enzyme that is used to convert glucose to fructose

Immobilised lactase

An immobilised enzyme that hydrolyses lactose to glucose and galactose in the production of lactose-free milk