Genetics

• Genetics


  A branch of Biology that deals with the study of genes, heredity and Variation in organisms
• Charles Darwin and Wallace's views

  1859
• Mendel's work laid the foundation for the understanding of genetics
• Chromosomes


  Thread-like structures located in the nucleus of cells that carry genetic information in the form of genes
• DNA


  The chemical that carries the genetic instructions in the cells of organisms
• DNA is a double helix structure
• Heredity


  The transmission of traits from parents to offspring
• Variation


  The ability of an organism to acquire traits or characters from its own parents
• Phenotype


  The physical or observable traits displayed by an organism
• Genotype


  The genetic makeup of an organism that produces the phenotype
• Dominant traits


  Traits that are expressed in the offspring when present
• Recessive traits


  Traits that are hidden or not expressed in the offspring when present
• Homozygous


  An individual with two similar genes that perform the same characters
• Heterozygous


  An individual with two different pairs of genes controlling different characters
• Haploid


  An organism with one set of chromosomes
• Diploid


  An organism with two sets of chromosomes
• Mutation


  A process whereby there is a slight alteration or change in the gene of an organism leading to the formation of new characteristics
• Genetic linkage


  The physical association of materials found on the same location, whereby genes can be inherited together due to their close association on a chromosome
• Sex linkage


  Traits that are associated with the sex chromosomes (X and Y)
• Sex-linked abnormalities


  • Colour blindness
  • Haemophilia (bleeding disease)
• Genetic linkage


  The physical association of genes on the same location, whereby genes can be inherited together due to their close association - it can take place on a chromosome
• Sex linkage


  It takes place in the Sex Chromosome. The X chromosome is larger in size and carries more genes, it moves faster than the Y chromosome which is smaller in size and carries less genes
• Abnormalities associated with sex linkage


  • Colour blindness
  • Haemophilia (Bleeding Disease)
  • Baldness
• Sickle cell anaemia


  An abnormality caused by recessive genes which cause the red blood cells of some organisms to become sickled shape
• Albinism


  A situation where the skin of an organism is non-pigmented (lacks melanin pigment)
• Crossing over


  A process that leads to exchange of genetic materials between chromosomes
• Example of crossing over


  • Parent 1 x Parent 2 = Recombinant offspring
• Genetic recombination


  The combination or exchange of genetic materials during meiosis
• Allele


  Different forms of the same gene
• Genetic population or population genetics


  The study of genetic variation and evolutionary changes in a particular area or population of organisms
• Genetic variation


  The different genes that occur in a population
• Gene pool


  The sum of all the varieties of genes present in a population, which changes from generation to generation
• Allele frequency


  How often a form of a gene shows up/reoccurs in a population over several generations
• Phenotypical variation


  The visible differences in phenotypes that exist in a population
• Random mating


  A situation where each and every organism in an environment have equal right of mating with other organisms of the same type
• Genetic diseases


  Disorders caused genetically, which have no environmental remedy but can only be controlled
• Mutation


  An alteration of genes or chromosomes that can lead to the formation of new characteristics
• Down Syndrome


  A genetic disorder caused by the failure of the 21st chromosome to separate during egg or sperm formation, resulting in an extra copy of the 21st chromosome
• Turner's Syndrome


  A monosomic disorder in females where they have only one X chromosome instead of two
• Klinefelter's Syndrome


  A disorder in males where they have an extra X chromosome, resulting in physical and fertility issues