Topic 6: Key words A-Z Flashcards
Allele
A version of a gene
Allopatric speciation
Specialisation that occurs when two populations become geographically isolated due to a physical barrier
Apoptosis
Programmed cell death
Autosomal linkage
2 or more genes are positioned on the same autosome. They are often inherited together as they are unlikely to be separated by crossing over in meiosis.
Autosome
A chromosome that is not an X or Y chromosome
Codominance
Both alleles for a gene in a heterozygous organism equally contribute to the phenotype
Continuous variation
Variation where there is no clear separation into distinctive categories (e.g height). It produces a continuous range where. a characteristic can take any value. Multiple genes influence it.
Deletion mutation
A nucleotide base is removed from a DNA sequence. This may lead to a frameshift mutation, triplets downstream will be different
Dihybrid inheritance
Inheritance of two genes determines a trait
Directional selection
Natural selection that produces a gradual change in allele frequencies over several generations.
Happens when there is a change in selection pressures or a new allele has appeared in the population that is advantageous
Discontinuous variation
Variation that can be categorised e.g blood group. Appears only in discrete vales. One or two genes influence it.
Disruptive selection
A type of selection that favours individuals with extreme phenotypes and selects against those with phenotypes close to the mean.
DNA ligase
Enzyme that joins the sugar phosphate backbone of two DNA segments
DNA profiling
Technique used to determine the patterns in a non coding DNA of an individual, where unique repeating patterns can be used to differentiate one person from another.
DNA sequencing
Determining the entire DNA nucleotide base sequence of an organism
Electrophoresis
A type of chromatography that separates nucleic acid fragments or proteins by size using an electric current.
Electroporation
An electric current is used transfer recombinant plasmids into the bacterial cells or fragments of DNA into eukaryotic cells
Electroporation
An electric current is used transfer recombinant plasmids into the bacterial cells or fragments of DNA into eukaryotic cells
Epistasis
Relationship between genes at different loci, where the allele of one gene effects the expression of a different gene
Evolution
The gradual change in allele frequency within a population over time, 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 a smaller gene pool and an increased frequency of rare alleles.
Gene mutation
A change to at least one nucleotide base in DNA or the arrangement of bases. Occur spontaneously during replication.
Gene therapy
A faulty allele is replaced with a functional allele to prevent or treat a disease
Genetic bottleneck
A drastic reduction in population size leading to reduced genetic diversity within a population.
Genetic drift
Random variations in allele frequency in small populations due to mutations
Genetic engineering
Modification of a genome of an organism by the insertion of a desired gene from another organism, enabling the formation of organisms with desired characteristics
Genotype
An organisms genetic composition, describing all alleles
Germ line cell gene therapy
A type of gene therapy in which the faulty allele is replaced with a functional allele in germ cells or a very early embryo, the effects are permanent and can be inherited.
Homeobox genes
A group of regulatory genes that contain a DNA sequence that is highly conserved in animals, plants and fungi. Responsible for the development of body plans in different organisms
Insertion
A form of gene mutation in which one or more nucleotide bases are added to a DNA sequence. This may lead to a frameshift mutation, changing every successive codon.
Intron
Non coding region of DNA
Lac operon
A group of three structural genes, lacZ, lacY and lacA, that are required for the
metabolism of lactose.
Mature mRNA
mRNA that has been modified by having introns removed
Monogenic inheritance
Determination of a trait by the inheritance of a single gene
Mutagen
A chemical, biological or physical agent that increases the rate of gene mutations above normal level.
Operon
group of genes that are expressed together and controlled by the same regulatory mechanism
PCR
Polymerase Chain Reaction - an in vitro technique used to rapidly amplify fragments of DNA
Repressor protein
A protein that binds to the operator altering transcription rate.
Restriction endonuclease
Enzymes that cut DNA molecules at recognition sequences, creating ‘stick ends’
Somatic cell gene therapy
A type of gene therapy in which a faulty allele is replaced with a functional allele in affected somatic cells. The effects of this are temporary and cannot be inherited.
Stabilising selection
Favours individuals with phenotypes close to the meaning selects against extreme phenotypes
Sticky ends
The staggered cut formed by endonuclease in double stranded DNA
Substitution mutation
A form of gene mutation in which one nucleotide base is exchanged for another. This may change an amino acid or produce the same amino acid (due to the degeneracy of the genetic code).
Sympatric speciation
speciation occurs in the absence of a geographical barrier. Random mutations may occur within the population which results in behavioural, mechanical, or temporal changes, which cause the organisms to become reproductively isolated.
