Genetics: From Genotype to Phenotype
1-13-10 through 1-15-10
Genotypes and Phenotypes
•genotype: genetic makeup of an individual.
•phenotype: observable feature of an organism.
•
•Example: obesity
Gregor Mendel
•first to demonstrate that heredity followed specific laws of inheritance.
•particulate inheritance: the concept of heredity based on the transmission of genes
according to Mendelian principles.
•Studied pea plant traits.
•
Mendel’s conclusions
•Forms of a trait are encoded in discrete packages (genes.)
•Alleles:
•
•homozygous: similar expression of a trait. (YY or yy)
•heterozygous: different expressions of a trait. (Yy)
•recessive:
•dominant: traits not expressed when heterozygous (Yy).
•Law of segregation: the pair of units controlling a trait separate into different sex cells
and then are united with another unit during fertilization (meiosis).
•Law of independent assortment:
Beyond Mendel
•qualitative variation: phenotypic variation belonging to discrete, observable
categories.
•quantitative variation: phenotypic variation as the distribution of continuous variation
within a population.
Examples?
•polygenic traits: