Transcript Chapter4ol

Chapter 4
Heredity and
Evolution
Epigenetics
• http://video.pbs.org/video/152510747
3/
• LA Times Article
Gregor Mendel
A monk living in
what is now the
Czech Republic
Living in an abbey
he crossed different
strains of purebred
plants and studied
their progeny.
His work illustrates
the basic rules of
inheritance.
Traits Mendel Studied in Peas
Dominance
• Dominant traits are governed by an
allele that can be expressed in the
presence of another, different allele.
– Dominant alleles prevent the expression of
recessive alleles in heterozygotes.
Recessiveness
• Recessive traits are not expressed in
heterozygotes.
– For a recessive allele to be expressed,
there must be two copies of the allele.