Mendel, Pea Plants, and Inheritance Patterns

AP BiologyFall 2010

Late 19th century, natural selection suggested that a population could evolve if members show variation in heritable

Variations that improved survival chances would be more common in each generation ◦ In time, population would change or evolve

Theory of Natural Selection did not fit with prevailing view of inheritance ◦ Blending

Blending would produce uniform populations; such populations could not evolve

Many observations did not fit blending ◦ White horse and black horse did not produce gray

ones

Gregor Mendel used experiments in plant breeding and knowledge of mathematics to form his hypotheses

Mendel used the garden peas for his experiments This plant can fertilize itself; true breeding

varieties were available to Mendel Peas can be cross fertilized by human

manipulation of pollen

Self fertilizing: flowers produce both male and female gametes

True breeding: successive generations will be like parents in one or more traits ◦ White flowered parent plants give rise to white flowered

offspring

Mendel hypothesized that clearly observable differences might help him track the trait and identify inheritance patterns and heredity

Genes: units of information about specific traits, each located at a particular locus on a chromosome

Homologous Chromosome: diploid cells have 2 genes (a gene pair) for each trait- each on a homologous chromosome

Mutation: alters a gene’s molecular structure Alleles: are various molecular forms of a

gene for the same trait

◦ Page 171, figure 11.4

True Breeding Lineage: occurs when offspring inherit identical alleles, generation after generation

Hybrid Offspring: what non-identical alleles produce

Homozygous: when both alleles are the same

Heterozygous: when the alleles differ When heterozygous one allele is dominant

(A) and the other allele is recessive (a)

Homozygous dominant: AA Homozygous recessive: aa Heterozygous: Aa Genotype: is the particular alleles an

individual carries Phenotype: is how the genes are

expressed physically (what you observe) P: true breeding parental generation F1: first generation offspring F2: second generation offspring of self

fertilized or intercrossed F1 individuals

Jeopardy