Unit 3: Genetics
Mendel and the Gene Idea
When Mendel mated two true-breeding varieties (the
generation), all of the offspring (the
generation) from this
Mendel proposed two principles of inheritance to explain his results.
"Heritable factors" (genes) have
If the two alleles at a locus differ, the organism is
, and the
allele determines the organism's
The two alleles
in meiosis, and rhe distribution of the segregated phenotypes can be calculated from a
model called the
How can we determine the genotype of an organism with the dominant
with an individual that is homozygous
Law of Independent
Crossing true-breeding parents differing in
in the F1 generation heterozygous for both characters, and
phenotypes in the F2 generation.
Each pair of alleles
and randomly during gamete formation, assuming they are on different
Mendel's laws are based on probability, and obey rules of
cross, the probability of allele
of the probabilities of allele frequencies in the
cross, the probabilities of multiple allele
of the probabilities of the individual
Extending Mendelian Genetics.
of the heterozygote and
homozygote are identical.
the phenotypes of homozygotes. An example is the flower color of
, two dominant alleles affect the phenotype. An example is the human blood group
where phenotypes are determined by
Some traits exhibit
inheritance which oftens shows
, a gene at one
may alter the phenotypic expression of a gene at a second locus. An example is the mouse coat
Inheritance in human families can be studied by
showing the inheritance of alleles across generations.
Feb 25, 2008