a
Each person has two alleles (containing genes) in each chromosome. The parent only passes one of these alleles from each of their 23 chromosomes onto their offspring. Some alleles are dominant and others are recessive. In traditional inheritance: if the dominant gene is present in either of the two alleles in the offspring, then that trait is displayed in the organism’s phenotype (physical appearance).
For instance if an offspring has an allele for the recessive trait of blondeness, but also has the dominant gene for dark hair- then the offspring will display the dark hair phenotype. In codominance both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other. An example of this is the classic case of a white flower reproducing with a red flower and producing pink offspring. Incomplete dominance is when both alleles are partially expressed; often producing an intermediate phenotype (a mixture of both traits without them mixing, think of a mosaic).Polygenic inheritance refers to inheritance of a phenotypic characteristic (trait) that is caused by two or more genes.
Diagram: http://www.accessexcellence.org/RC/VL/GG/images/MENDEL.gif
Youtube Video: http://www.youtube.com/watch?v=prkHKjfUmMs&feature=related
Five Questions (Punnett Squares as instructed.) Simple Punnett Squares:
A a a a a
A A

sy
Y y y y
A a
A a
Dihybrid Crosses:
SY Sy sY
SY
Sy sY sy

a a a
Vocab
Alleles- One member of a pair or series of genes that occupy a specific position on a specific chromosome.
Autosomal: the gene responsible for the phenotype is located on one of the 22 pairs of autosomes (nonsex determining chromosomes).
X-linked: the gene that encodes for the trait is located on the X chromosome.
Dominant: conditions that are manifest in heterozygotes (individuals with just one copy of this allele).
Recessive: conditions are only manifest in individuals who have two copies of this allele (are homozygous).
Answers
A a a Aa aa
Aa aa
A
Aa
A
Aa
Aa Aa y y

sy
Y y
Yy Yy yy yy
A a
A AA Aa
Dihybrid Crosses:
SY Sy sY a Aa aa sy
SY SSYY SSYy SsYY SsYy
Sy SSYy SSyy SsYy Ssyy sY SsYY SsYy ssYY ssYy
SsYy Ssyy ssYy ssyy