Topic 6 - Inheritance, Variation and Evolution

• Vector


  A carrier used to transfer a gene from one organism to another.
• Variation


  The differences between individuals due to genes, the environment or a combination of both.
• Tissue culture


  A method of growing living tissue or cells in a suitable medium to produce clone plants.
• Three-domain system


  A method of classification in which organisms are categorised into three groups; Archaea, Bacteria and Eukaryota. Developed by Carl Woese.
• Species


  A group of similar organisms that are able to breed with one another to produce fertile offspring.
• Speciation


  The formation of new species in the course of evolution, often due to the evolution of two isolated populations.
• Sexual reproduction


  A form of reproduction involving the fusion of male and female gametes. Creates genetic variation.
• Sex chromosomes


  A pair of chromosomes responsible for the determination of gender. XY in males. XX in females.
• Selective breeding


  The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with desirable phenotypes.
• Ribosomes


  Sub-cellular structures where protein synthesis takes place.
• Recessive


  Describes an allele that is only expressed in the absence of a dominant allele. Represented by a small letter.
• Punnett square


  A grid used to predict the potential outcomes of a genetic cross.
• Protein synthesis

  The formation of a protein from a gene.
• Polydactyly


  A condition where an individual is born with extra fingers or toes due to the presence of a dominant allele.
• Phenotype


  An organism's observable characteristics. Due to interactions of the genotype and the environment.
• Nucleotides


  The monomers of DNA consisting of a common sugar, a phosphate group and one of four chemical bases (A, T, C, G) attached to the sugar.
• Non-coding DNA


  DNA which does not code for a protein but instead controls gene expression.
• Natural selection


  The process by which the frequency of advantageous traits passed on in genes gradually increases in a population over time.
• Mutation


  A random change in DNA which may result in genetic variants.
• MRSA


  A type of bacteria that is resistant to the antibiotic, methicillin.
• Mitosis


  A form of cell division that produces two genetically identical daughter cells (with a full set of chromosomes) from one parent cell.
• Meiosis


  A form of cell division that produces gametes, non-identical cells with half the usual number of chromosomes.
• Linnaen system


  The classification of organisms into kingdom, phylum, class, order, family, genus and species, as developed by Carl Linnaeus.
• Inbreeding


  The formation of offspring from the breeding of closely related individuals.
• Homozygous


  When someone has two identical alleles of a gene e.g. ff.
• Heterozygous


  When someone has two different alleles of a gene e.g. Ff.
• GM crops


  Crops that have had their genomes modified by the insertion of a desired gene from another organism.
• Genotype


  An organism's genetic composition. Describes all alleles.
• Genome


  The complete genetic material of an organism.
• Genetic engineering


  The modification of the genome of an organism by the insertion of a desired gene from another organism, enabling the formation of organisms with beneficial characteristics.
• Gene


  A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein.
• Gametes


  Sex cells (sperm and egg cells) with half the usual number of chromosomes.
• Fossil


  The remains of dead organisms found in rocks which are millions of years old.
• Fertilisation


  The fusion of the nucleus of male and female gametes. Restores the full chromosome number.
• Family tree


  A chart used to show the inheritance of a condition in a family.
• Extinction


  The death of all members of a species.
• Evolutionary tree


  A diagram which illustrates the evolutionary relationships between organisms.
• Evolution


  The gradual change in the inherited traits within a population over time. Occurs due to natural selection.
• Embryo transplants


  The simplest method of animal cloning. Cells are removed from a developing embryo, split apart and grown in culture, before being transplanted into host mothers.
• Embryo screening


  A procedure used to determine the presence of faulty genes in an embryo produced by IVF. A few embryonic cells are removed and screened for defective alleles.