BIO 10 Lecture 10. REPRODUCTION: CHROMOSOMES AND HEREDITY. An Introduction to Mendel and His Peas: 1856-1863. Research in Brno, Czech Republic
CHROMOSOMES AND HEREDITY
Research in Brno, Czech Republic
Observed the inheritance patterns of seven inherited physical characteristics in several generations of pea plantsand applied mathematics to discover the two basic laws that govern their behavior
Did his work before chromosomes (1880's) or DNA (1950's) had been discovered
Was a monk who grew his pea plants in the monastery garden
Complex organisms carry two copies of each gene but pass only one copy to each gamete
Each gene controls a single trait (e.g. seed color) but different forms of the same gene (alleles) can confer different expressions of that trait (e.g. yellow vs. green seeds)
Mendel's First Law: Law of Segregation
In a heteroygote, only one allele is physically expressed; this allele is dominant(A) over the unexpressed, recessive(a)allele.
Law of Segregationcontinued...
Yy = yellow
yy = green
Punnett Square predicts
3:1 phenotypic ratio
Therefore, a dihybrid will create 4 different types of gametes in equal proportions: AB, ab, Ab, and aB
Mendel's Second Law: Law of Independent Assortment
How many gametes, and what types, can be produced by a pea plant with the genotype PP? How about Pp? pp?
How many gametes, and what types, can be produced by a pea plant with the genotype PpTt? How about PPTt?
How many gametes, and what types, can be produced by a pea plant with the genotype PpTtYy? How about PPTtYy?