Bio 1

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...