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Genes (Beyond Mendel (degree of dominance (codominance (Tay-Sachs disease,…

- - - - in which heterozygotes show a distinct
        intermediate phenotype not seen in homozygotes.
    - - such as Mendel's crosses
    - - in which two alleles affect
        the phenotype in separate, distinguishable ways
      - Tay-Sachs disease
        
        lack a functioning enzyme to metabolize certain lipids. These lipids accumulate in the brain, harming brain cells and ultimately leading to death
        
         Children with two Tay-Sachs alleles (homozygotes) have the disease.
        
         Both heterozygotes, with one allele coding for a functional enzyme, and homozygotes, with two such alleles, are healthy and normal.
  - - - the additive effects of two
        or more genes on a single phenotypic character.
    - - The product of a genotype is generally not a rigidly defined phenotype, but a range of
        phenotypic possibilities, the norm of reaction, determined by the environment.
      - Norms of reaction are broadest for polygenic characters.
        For these multifactorial characters, genes and environment influence phenotype
  - - - can be used from the 14th to 16th week of pregnancy to assess whether the fetus has a specific disease
      - Fetal cells extracted from amniotic fluid are cultured and karyotyped to identify some disorders
      - Other disorders can be identified from chemicals in the amniotic fluids.
    - - allows faster karyotyping and can be performed as early as the 8th to 10th week of pregnancy
      - A sample of fetal tissue is extracted from the chorionic villi of the placenta.
      - Recent techniques allow the isolation of fetal cells or DNA from the mother’s blood
- - - - pea plants
        
        traits
        
        different variants of distinct characters
        
        characters
        
        distinct heritable feature
  - - - alleles
        
        recessive- no noticeable effect
        
        dominant- determines appearance
  - - - When true-breeding plants self-pollinate, all their offspring have the same traits as their parents
    - - hybridize
        
        cross breed
      - hybrid offspring are
        the F1 (first filial) generation.
      - true-breeding parents are the P (parental) generation
      - F1 hybrids to self-pollinate to produce an F2 (second filial)
        generation