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Classical Genetics

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					 Classical Genetics

The “Old School” way of heredity!
Eckert – Minerva DeLand Science
Vocabulary
P generation
 (parent) 1st group crossed


F1 generation
 (first filial) offspring of parent generation


F2 generation
 (second filial) offspring of F1
Vocabulary
Hybrid
 Offspring of two pure parents
  ex. BB x bb = Bb          hybrid
Vocabulary
Dominant
 A trait that, when present, expresses itself


Recessive
 A hidden trait
Vocabulary
Gene
 Carried by chromosomes in a definite
  order
 2 genes are needed to express a trait
Vocabulary
             Chromosomes
              Found in nucleus
              Hereditary information
Vocabulary
Alleles
 Different copies or forms of a gene
  controlling a trait
Vocabulary
Homozygous
 Alleles for a trait are the same


Heterozygous
 Alleles are different
Vocabulary
Genotype
 Genetic makeup of an organism


Phenotype
 The physical trait that an organism
  develops as a result of its genotype (tall,
  short, etc)
Gregor Mendel
   Investigated
    inheritance with pea
    plants
   Developed principles
    that are still accepted
    today
Mendelian Laws and Genetic
Principles
Law of Dominance
 When an organism is hybrid
   Only   the dominate trait is expressed

TT = Tall
Tt = Tall
tt = short
Law of Segregation
 Individuals are controlled by a pair of
  genes
 Pairs of genes are separated from each
  other during meiosis and recombine at
  fertilization
The Gene-Chromosome Theory

 Genes make up chromosomes
 Arranged in definite order (like beads on a
  necklace)
The Law of Probability
           Chance
           Several possible events
            that might happen will
            occur in equal numbers
            over a large number of
            trials
Principle of Independent
Assortment
   During meiosis, genes from different traits
    are separated and distributed to gametes
    independently of one another
Pedigrees
Heredity in humans cannot be studied the
   same way as in plants and animals for 3
   reasons
1. Time between generations is too long
2. # of offspring is too small
3. No controlled experiments are possible
Pedigrees
One can learn genetic traits in humans by
 tracing the appearance of these traits in
 families over several generations by using
 a pedigree chart. This is a diagram that
 shows the presence or absence of a
 particular trait in each member of each
 generation.

				
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posted:5/17/2013
language:English
pages:17