Genes and Inheritance

• Diploid


  Two sets of chromosomes (2n)
• Haploid


  One set of chromosomes (n)
• Chromosomes


  A thread-like structure composed of DNA and protein
• Gene


  A section of DNA that codes for proteins
• Allele


  The different forms of a gene
• Aneuploidy


  Fertilisation of an abnormal gamete results in abnormal chromsome number
• Monosomy


  A cell or organism has only one copy of a particular chromsome
• Trisomy


  A cell or organism has three copies of a particular chromosome
• Metacentric


  Centromere positioned in the middle of chromosomes

  
• Submetacentric


  Centromere positioned towards one end

  
• Acrocentric


  Centromere positioned very close to one end

  
• Telocentric


  Centromere positioned at tip of chromosomes

  
• Dominant Gene


  A type of gene that only requires one copy in order for it to show in the phenotype
• Recessive Gene


  A type of gene that requires two copies in order for it to show in the phenotype
• Gamete


  An egg or sperm cell
• Genome


  The sum total of an organism's DNA
• Locus


  The position of a gene on a chromosome

  Plural: loci
• Non-Homologous


  Chromosomes that are not similar in size, shape, band pattern and centromere positioning
• Homologous


  Chromosomes that are similar in size, shape, band pattern and centromere positioning
• Incomplete Dominance


  A situation in which one allele is not completely dominant over another allele, neither allele is fully dominant nor fully recessive
• Codominance


  A situation in which there are two alleles for a given gene locus and both alleles are expressed in the phenotype