Chapter 11: Introduction to Genetics

Chapter 11: Introduction to Genetics

1. Gregor Mendel

   • Born in 1822 in the Czeh Republic
   • Priest, scientist, mathmaticion, teacher, gardener
   • Studied the inheritance of traits in garden peas

2. Mendel's Work

   • Fertilization - joining of male and female reproductive cells during sexual reproduction
   • True-breeding - offspring of self-pollinated plants produce offspring identical to itself
   • Cross-pollinate
     • Hybrid - the offspring of a cross between parents with different traits

3. Pea flowers normally self pollinate - sperm cells in pollen fertilize egg cells within the pistil of the same flower

4. Traits

   • Dominant - expressed by TT or Tt
   • Recessive - expressed when the dominant allele is not present( tt )
   • Given that recessive traits re-appear in the F2 generation, alleles must have segregated when gametes were formed

5. Terms

   • Probability - the likely-hood that a particular event will occur
     • Can be used to predict the outcome of genetic codes
   • Homozygous - 2 identical alleles
   • Heterozygous - 2 different alleles
   • Phenotype - physical characteristics
   • Genotype - genetic makeup
   • Principle of Independent Assortment: genes for different traits can segregate independently during gamete formation. This accounts for many genetic variations in organisms
   • Codominance - both phenotypes are produced
   • Multiple Alleles - a gene with more than 2 possible alleles in a population
   • Polygenic traits - traits controlled by 2 or more genes
     • Western White Butterfly
       • When adults hatch in spring, wings are darker than those that hatch in summer. The dark wing color helps increase their body heat in the cooler spring.
   • Diploid(2N) - a cell contains both sets of homologous chromosomes
   • Haploid(N) - contains a single set of genes; Gametes(sex cells) are haploid
   • Homologous Chromosomes - a pair of chromosomes that carry genes coding for the same characteristics
   • Tetrad - a pair of homologous chromosomes; includes 4 chromatids
   • Crossing Over - alleles are exchanged between homologous chromosomes when they are lined up as tetrads; produces a new combination of alleles; contributes to genetic diversity

6. Meiosis

   • Process when gametes are formed; homologous chromosomes are separated to create haploid gamates; 1 diploid = 4 haploid

7. Can't assort independently, they are linked together because they are on the same gene. So, their alleles tend to be inherited together. Crossing over can be done and separate linked genes. The loser together genes are on a chromosome the more likely they will be inherited together.

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