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Genetics, Chromosomal Genetics - Coggle Diagram

- - - - Dihybrid Cross
        
        Tracks inheritance of two characters
      - Test Cross
        
        Crosses an unknown dominant phenotype with a homozygous recessive to determine the unknown genotype
      - Monohybrid Cross
        
        Tracks inheritance of one character
    - - Allele pairs for different genes segregate independently during gamete formation
      - Applies to genes on different chromosomes (unlinked)
  - - - Probability of multiple independent events occurring together is the product of their individual probabilities
    - - Probability of any one of several mutually exclusive events occurring is the sum of their individual probabilities
- - - - Incomplete Dominance
        
        Heterozygote phenotype is intermediate (blended) between the two parental phenotypes
      - Codominance
        
        Both alleles are fully and separately expressed in the heterozygote (e.g., AB blood)
      - Multiple Alleles
        
        More than two alleles exist for a gene in the population (e.g., ABO blood group)
    - - Pleiotropy
        
        One gene influences multiple phenotypic traits (e.g., sickle-cell disease)
      - Epistasis
        
        One gene at one locus alters or masks the expression of a gene at a second locus
      - Polygenic Inheritance
        
        Two or more genes have an additive effect on a single quantitative trait (e.g., skin color)
  - - - A family tree used to deduce the pattern of inheritance (e.g., dominant vs. recessive)
- - - - Pea Plants
        
        Model organism used to study inheritance
      - True-breeding
        
        Organisms that produce only the same variety (homozygous) upon self-pollination
      - Hybridization
        
        The process of crossing two true-breeding varieties
      - Character
        
        heritable feature
      - variant of that feature
    - - Dominant/Recessive
        
        The Dominant allele determines phenotype in a heterozygote; Recessive effect is masked
      - Law of Segregation
        
        The two alleles for a trait separate into different gametes during meiosis
      - Alleles
        
        Alternative versions of a gene
    - - Homozygous
        
        identical alleles (PP,pp)
      - Heterozygous
        
        different alleles (Pp)
      - Phenotype
        
        The organism's observable physical traits (appearance).
      - Punnett Square
        
        Diagram used to predict allele combinations in offspring
      - Genotype
        
        The organism's genetic makeup (allele combination)
- - - - Exchange of DNA between homologous chromosomes during meiosis
    - - Measures how often crossing over separates linked genes; used to create linkage maps (1% frequency = 1 map unit)
  - - - Genes on the X chromosome; males (XY) are hemizygous (express any single allele)
    - - In female cells, one X chromosome is randomly silenced (forms a Barr body)
  - - - Offspring traits match the parents (most common)
- - - - Changes like Deletion (loss), Duplication (repeat), Inversion (flip), or Translocation (move to non-homologous)
    - - Abnormal number of chromosomes (e.g., Trisomy has three copies, Monosomy has one)
    - - Chromosomes or chromatids fail to separate correctly in meiosis/mitosis
  - - - Gene expression depends on the parent that contributed the allele (often involves methylation)
    - - Genes found in mitochondria/chloroplasts (outside the nucleus)
    - - Extranuclear genes are inherited only from the mother (via the egg cytoplasm)
- - - - Morgan's fruit fly experiments showed that a gene (for eye color) was located on the X chromosome
    - - The behavior of chromosomes in meiosis (separation) explains the rules of inheritance
    - - Genes sit on chromosomes at specific loci (positions)