Genetics and evolution

• Transcriptional control

  Example: lac operon in E.coli
• Beneficial mutations

  • Humans developing trichromatic vision
• Mutations


  1. Changes in the sequence of nucleotides in DNA molecules

  2. Types of mutations include: Insertion/deletion mutations, Point mutation/substitution, Nonsense mutation, Missense mutation, Silent mutation
• Effect of mutations on organisms

  Depends on the environment of the organism
• Post-transcriptional control

  Editing of primary mRNA transcript by removing introns and keeping exons
• Transcriptional control

  Explanation of how transcription of structural genes is inhibited or allowed based on glucose and lactose concentrations
• Genetic control

  Homeobox genes involved in controlling the development of body plans by regulating transcription
• Apoptosis


  A form of programmed cell death that controls the development of body plans
• Neutral effects of mutations

  Mutations that cause no change to the organism, occur in non-coding regions of DNA, or are silent mutations
• Transcriptional control

  Regulator gene coding for the inhibitor protein located outside the operon
• Controlling gene expression

  Can be controlled at transcriptional, post-transcriptional, and post-translational levels
• Harmful mutations


  • Mutation in the CFTR protein causing cystic fibrosis
• Genetic control

  • Homeobox genes aiding in limb formation in humans
• Transcription factors


  Ability to switch genes on and off by interacting with the promoter sequence of DNA
• Post-translational control


  Example: Activation of proteins like adrenaline with cyclic AMP
• Apoptosis


  A form of programmed cell death which can act as a mechanism to control the development of body plans such as fingers and toes
• Meiosis

  1. Form of cell division that gives rise to genetic variation by producing haploid gametes with half the number of chromosomes

  2. Genetic variation achieved through crossing over of chromatids and independent assortment of chromosomes
• Apoptosis


  Enzymes break down the cytoskeleton of the cell, DNA, and proteins. Cell shrinks, breaks up, and fragments are engulfed by phagocytes and destroyed
• Sex linkage is the expression of an allele dependent on the gender of the individual, for instance, haemophilia
• Monogenic inheritance is when a phenotype or trait is controlled by a single gene, for instance, cystic fibrosis
• Epistasis is the interaction of different loci on the gene where one gene locus affects the other gene locus
• Dominant epistasis is when a dominant allele at one locus completely masks the alleles at a second locus
• Linkage is the phenomenon where genes for different characteristics are located at different loci on the same chromosome and inherited together
• Patterns of inheritance

  • Phenotypic variation: Discontinuous and continuous
  • Influenced by environmental factors such as diet in animals and etiolation and chlorosis in plants, and genetic factors
• Gene transcription


  Switching genes on and off when they are required at particular stages of development, for instance during limb formation in humans
• Dihybrid cross involves the inheritance of two genes
• The chi-squared test is a statistical test used to determine the significance of the difference between observed and expected data
• Apoptosis


  • Ordered, controlled series of biochemical events leading to cell death
  • Opposite of necrosis, which is cell death resulting from damage and release of hydrolytic enzymes
  • Means of controlling the number of cells to prevent cancer
• Autosomal linkage refers to genes located on the same chromosome (not a sex chromosome) and tend to be expressed together in the offspring
• Recessive epistasis occurs when the presence of a recessive allele prevents the expression of another allele at a second locus
• Hardy-Weinberg principle

  p2 = frequency of AA (homozygous dominant), 2pq = frequency of Aa (heterozygous), q2 = frequency of aa (homozygous recessive)
• If the chi squared value is greater than the critical value, the null hypothesis is rejected, meaning the difference between observed and expected results is not due to chance
• Recessive epistasis gives the ratio of 9:3:4
• Hardy-Weinberg principle


  For a population in genetic equilibrium: p + q = 1.0 (The sum of the frequencies of both alleles is 100%)
• The chi squared test is a statistical test which can be used to establish whether the difference between observed and expected results is small enough to occur purely due to chance
• Organisms are adapted to their environment in various ways

  • Anatomical adaptations, Behavioural adaptations, Physiological adaptations
• The chi squared test can determine whether the null hypothesis is correct or not, where the null hypothesis assumes no difference between observed and expected results
• Evolution is the process by which the frequency of alleles in a gene pool changes over time as a result of natural selection
• Factors that can affect the evolution of a species include genetic drift, genetic bottleneck, and founder effect
• Dominant epistasis gives the ratio of 12:3:1