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Date Submitted: 09/23/2013 11:43 PM
Mendelian genetics
Blending concept of inheritance
Offspring would have traits intermediate
Example: A cross between red and white flowers would produce pink flowers
A blending theory did not account for variation and could not explain species diversity
Mendel’s particulate theory of inheritance
Mendel was an Austrian monk that studies science with a math background
Mendel’s particulate theory is based on the existence of minute particles—now called
genes.
Mendel prepared his experiments with garden pea, Pisum sativum
easy to cultivate
short generation time
cross-pollinated by hand
Mendel studied simple traits (e.g., seed shape and color, flower color, etc.)
Mendel’s Law
Law of Segregation
Mendel confirmed that his tall plants always had tall offspring, i.e., were true-breeding
monohybrid cross is between two parent organisms for two distinct forms of one trait
Mendel tracked each trait through two generations
Contrary to blending theory of inheritance
Characteristics of other parents reappeared
1/4 of F 2 plants
3/4 of F 1 plants
Mendel saw that these 3:1 results were possible if:
two factors for each trait, one being dominant and the other recessive
random fusion of all possible gametes occurred upon fertilization
Law of Segregation:
Each organism contains two factors for each trait
Factors segregate during the formation of gametes
Each gamete contains one factor for each trait
Fertilization gives each new individual two factors for each trait
concept and terms
Locus is the specific location of alleles on homologous chromosome
Alternative versions of a gene are called alleles
Dominant allele masks or hides expression of a recessive alleles
Recessive allele is an allele that exerts its effect only in the homozygous state
True-breeding - two identical alleles for a trait–they were homozygous
Homozygous dominant
Homozygous recessive
Heterozygous genotypes possess one of each allele for a particular trait.
Genotype...