Please enable JavaScript.

Coggle requires JavaScript to display documents.

Mendel and the Gene Idea (Human traits follow patterns of inheritance…

- - - - Phenotype
        
        physical appearance
        
        I.e. flower color in pea plants, PP and Pp have the same phenotype (purple) but different genotypes
        
        An individual with we dominant phenotype is either homozygous dominant or heterozygous
      - Genotype
        
        genetic makeup
        
        if any offspring display the recessive phenotype, the mystery parent must be heterozygous
      - Testcross
        
        Breeding the mystery individual with a homozygous recessive individual
        
        If any offspring display the recessive phenotype, the mystery parent must be heterozygous
- - - - Alleles are heterozygous
      - A gene has more than two alleles
      - A gene produces multiple phenotypes
    - - Complete Dominance
        
        Phenotypes of the heterozygote and dominant homozygote are the same
      - Incomplete Dominance
        
        The phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties
      - Codominance
        
        Two dominant alleles affect the phenotype in separate, distinguishable ways
      - Dominance/Phenotype
        
        In pea shape, dominant allele codes for enzyme that converts unbranched to branched form of starch
        
        The recessive allele codes for a defective form of the enzyme, causing clustering of unbranched starch (causes water to enter the seed, wrinkling as it dries)
        
        Tay-Sachs disease is a dysfunctional enzyme causing a cluster of lipids in the brain
        
        Biochemically, the phenotype is incompletely dominant
        
        organismally, the allele is recessive
        
        Molecularly, the alleles are codominant
      - Frequency of Dominant Alleles
        
        Dominant alleles are not necessarily more common in populations than recessive alleles
        
        Polydactyly (born w/ extra toes/fingers) is caused by a dominant allele, found much less frequently in the population than the recessive allele
    - - Most genes exist in ore than two allelic forms
      - Ex.
        The four phenotypes of the ABO blood group in humnans are determined by three alleles for the enzyme that attaches A or B carb to red blood cells IA, IB, and i
      - The enzyme encoded by the IA allele adds the A carb; IB allele adds B carb; i allele adds neither
    - - Genes have multiple phenotypic effects
      - Pleiotropic alleles are responsible for the multiple symptoms of certain hereditary diseases, such as cystic fibrosis and sickle-cell
  - - - gene expression at one locus changes the phenotypic expression of a gene at a second locus
      - Ex.
        Labrador coat color. B for black and b for brown, while other gene determines if the pigment will deposit in hair. E for color and e for no color
    - - Quantitative characters vary in the population along a continuum
      - Quantitative variations usually indicates polygenic inheritance (additional effect of two or more genes on a single phenotype)
      - Ex.
        Height - over 180 genes affect height
        skin color