Genetics and Evolution

• Genetics is the study of the transmission of traits from parents to offspring and the variation between and within generation.
• Meiosis reduces the number of chromosomes in gametes to half the number of chromosomes in the parent cell.
• A gene's locus is its location on a chromosome.
• A karyotype is an ordered display of an individual's condensed chromosomes.
• What are the three laws of Genetics from Mendel?

  1. Law of Segregation
  2. Law of Independent Assortment
  3. Law of Dominance
• WIlliam Harvey (1651)

  OMNE VIVUM EX OVO - All life comes from eggs
• Preformation is when the embryo is a miniature adult.
• Epigenesis is when adult forms arise by development from different forms.
• Genotype is the genetic makeup of an organism.
• Phenotype is the observable expression/physical traits
• Louis Pasteur: swan neck flask experiment
• Frederick Griffith: pathogenic and non-pathogenic streptococcus pneumonia
• Alfred Hershey and Martha Chase: tracing of sulphur and phosphorus in phage infection of bacteria
• An allele is one of several possible forms of a gene.
• Principle of segregation states that alleles separate during gamete formation.
• The study of heredity is known as genetics
• Color blindness, sickle cell anemia, down's syndrome and thalassemia are the human disorder that does not follow mendelian pattern of inheritance.
• Law of Independent Assortment: traits are inherited independently of each other.
• Polygenic Inheritance -> additive -> Eg. Skin colour
• Polygenic Inheritance->epistatic-> Eg. albinism
• Dominant epistasis: the dominant effects of one gene masks the effects of another. E.g. summer squash coloration
• Recessive epistasis: the recessive effects of one gene masks the phenotypic effects of another. E.g. coat colour in dogs
• Complete dominance- the phenotypes of the heterozygote and the dominant homozygous is indistinguishable.
• Incomplete dominance- neither allele is completely dominant, and the F1 hybrids have a phenotype somewhere
• Codominance- both phenotypes expressed in heterozygotes
• Pleiotrophy- one gene affects multiple phenotypic traits. e.g. ABO blood group alleles
• Epistasis- the phenotypic expression of one gene affects the expression of another gene.
• Polygenic Inheritance- a single phenotypic character is affected by two or more genes. E.g. height, skin pigmentation
• Multi factorial- (many factors, both genetic and environmental, collectively influence phenotype.
• Heterozygote with sickle-cell trait reduces malaria symptoms
• Recessively Inheritaged Disorders


  albinism, cystic fibrosis, tay-sachs disease, sickle cell
• Dominantly Inherited Disorders


  Anchondroplasia(dwarfism), Huntington‘s disease
• Multifactorial disorders


  Heart disease, diabetes, cancer, alcoholism, certain mental illnesses such as schizophrenia and bipolar disorder.
• Darwin explained three broad observation: 1. the unity of life, 2. The diversity of life , 3. The match between organisms and their environment
• The human genome is ~3pg and ~3Gbp
• Microsatellites are one of the main causes of genetic mutation
• Gene capacity calculated by genome size(bp) / average length of a gene (bp)
• Genetic drift is the effect of chance on a populatoon‘s gene pool
• Adaptive evolution- increase in frequency of beneficial alleles and decrease in deleterious alleles due to selections
• Bottleneck effect- magnification of genetic drift as a result of natural events or catastrophe