Genetics and Personality 1

• Genetics

  The study of the process of inheritance of certain genes passed from parents to their children
• Genotype/Phenotype

  • A person's genes (genotype) influence/determine their observable characteristics (phenotype).
  • E.g., appearance, behaviour, disease risk.
• Abnormal traits (anomalies)


  • Major effect on quality or length of life (e.g., Huntington's disease)
  • Some impact on health and/or wellbeing (e.g., colour blindness)
  • No impact on health or wellbeing
• Genome


  The collection of all of the genetic information; i.e., the different types of sequences that make up the total DNA of a human cell
• Human cells

  • 46 chromosomes: 22 pairs of autosomes, 1 pair of sex chromosomes (X,Y)

  
• Chromosome


  Contains a single DNA molecule

  
• Locus


  Location of a gene/marker on the chromosome

  
• Allele


  One variant form of a gene/marker at a particular locus
• DNA

  A nucleic acid containing genetic instructions specifying the biological development of all cellular forms of life
• DNA

  • Four nitrogenous bases - nucleotide
  • Only complementary bases can pair (AT or TA, GC or CG)

  
• Gene


  Basic unit of genetic information; sequences of bases that code for a protein. Genes determine the inherited characteristics
• Mutation


  An irreversible change in the DNA sequence of an organism
• Polymorphism


  Alternative forms of an allele resulting in distinct phenotypes
• Mutation vs Polymorphism

  • Mutation can directly contribute to a disorder and follows a Mendelian pattern of inheritance, rare
  • Polymorphism confers an increased risk, but does not directly cause disorder and has no clear inheritance pattern, common in population
• Forms of Genetic Variations

  • Single nucleotide substitution (SNPs)
  • Microsatellites (tandem repeats of 16 base pairs)
  • Minisatellites (tandem repeats of 6-100 base pairs)
  • Deletions or insertions (loss or addition of one or more nucleotides in a gene)
  • Changes in chromosome number and segment rearrangements
• SNPs


  • Replacement of one nucleotide with another, around 510 million in the human genome, two of every three involve C to T replacement, can occur in coding and non-coding regions
• Microsatellites


  • Tandem repeats of 16 base pairs, di-, tri-, and tetra-nucleotide repeats, second most abundant genetic variation, usually have no functional effect
• Minisatellites


  • Tandem repeats of 6-100 base pairs, occur at 1000 locations, usually have no functional effect
• Deletions or insertions


  • Loss or addition of one or more nucleotides in a gene, the protein the gene makes may not function properly or the function may be altered
• Changes in chromosome number and segment rearrangements

  • Down syndrome (chromosome 21), Edward syndrome (chromosome 18), Patau syndrome (chromosome 13), Klinefelter's syndrome (extra X chromosome)
• Dominant vs Recessive

  A dominant allele is expressed even if paired with a recessive allele, a recessive allele is only visible when paired with another recessive allele
• Autosomal recessive


  A disease appears in male and female children of unaffected (carrier) parents if two copies of the affected gene are inherited

  
• Autosomal dominant


  A person needs only one copy of the defective gene to develop the disorder. Affected males and females appear in each generation of the pedigree
• X-linked recessive


  • All the daughters of an affected male are "carriers"
  • Many more males show the disorder
  • None of the sons of an affected male show the disorder or are carriers
• Co-dominant inheritance


  Two different versions (alleles) of a gene can be expressed, and each version makes a slightly different protein. Both alleles influence the genetic trait or determine the characteristics of genetic condition.
• Mitochondrial inheritance


  Applies to genes in mitochondrial DNA (maternal inheritance)

  
• Mitochondrial disorders


  • Can appear in every generation of a family and can affect both males and females, but fathers do not pass mitochondrial traits to their children

  
• Behavioural Genetics


  The investigation of the associations between genetics and behavioural characteristics (e.g., personality), also considers the role of environment