Topic 3 - Analysing Variation Flashcards
What is a candidate gene?
A gene that, from the known or predicted biochemical properties of its product, is possibly responsible for a particular phenotype
Explain how polymerase chain reaction (PCR) works
A laboratory technique for amplifying a few copies of a DNA sequence (template) to generate thousands or millions of copies by a series of in vitro reactions using DNA polymerase. The reaction typically consists of 30–40 cycles that each has three parts: denaturation of DNA template, annealing of primers, and synthesis of DNA.
Why are neutral alleles useful markers in genetic mapping?
Because they have no phenotypic effect, they are not themselves subject to a selective pressure.
What is a quantitative trait locus (QTL)?
Quantitative trait loci (QTLs) are stretches of DNA linked to, or containing, the genes that underlie a specific trait.
Neutral alleles do not influence the phenotype of the organism, and therefore cannot be recognised by examination of the phenotype. What technique that you have already encountered could be used to identify a neutral allele?
Neutral alleles can be identified by molecular techniques such as PCR.
What are DNA microsatellites?
Microsatellites are short stretches of repeated sequences, such as repeated dinucleotides or trinucleotides, which are dispersed around the genome.
What are DNA simple sequence repeats?
Short stretches of DNA sequences repeated in a tandem fashion many times. Microsatellites are an example of simple sequence repeats.
What are restriction fragment length polymorphisms (RFLPs)?
A restriction fragment length polymorphism (RFLP) is a difference between two homologous DNA sequences that can be visualised as DNA fragments of different lengths after digestion of the DNA samples in question with specific restriction endonucleases.
Explain Southern blotting
Southern blotting (named for molecular biologist Ed Southern, who devised the technique) is a technique in which DNA fragments are first separated by agarose gel electrophoresis, before transferring them to a membrane for detection of specific sequences by hybridising with a tagged or labelled DNA probe consisting of the sequence of interest.
What are single nucleotide polymorphisms (SNPs)?
Loci within the genome where different individuals differ at single base pairs.
What are transposable elements in DNA?
Transposable elements are segments of DNA which can excise from one location in the genome and insert in another location.
What are transmembrane domains?
Transmembrane domains are regions of a protein which traverse a membrane.
What are G-protein-coupled receptors (GPCRs)?
G-protein-coupled receptors (GPCRs)
A family of integral membrane proteins that activate signal transduction processes inside cells; they typically bind extrinsic signals via their carboxy-terminal extracellular domains, and via a conformational change alter the activity of associated GTP-binding proteins. They are sometimes referred to as 7-helix transmembrane (7TM) receptors, serpentine receptors or heptahelical receptors because they possess seven transmembrane domains. GPCRs can also be considered as guanine nucleotide-exchange factors since they promote the exchange of GTP for GDP on associated G-proteins.
What is a ‘conservative amino acid change’?
One that replaces an amino acid residue with another with similar chemical characteristics.
