Download exceptions to mendel`s principles

EXCEPTIONS TO MENDEL’S PRINCIPLES
A. INCOMPLETE DOMINANCE – one allele is not completely dominant over the
other and the heterozygous phenotype is somewhere between the two
homozygous phenotypes.
Example: Japanese four o’clock plants (use lower case letters: rr,ww,rw)
Red (rr), white(ww), pink (rw)
Problems:
1. Cross a red Japanese four o’clock plant with a white flowered one.
2. Cross a pink Japanese four o’clock plant with another pink one.
B.CODOMINANCE - both alleles contribute to the phenotype (use capital letters)
Examples: Andalusian fowl (chickens)- black feathers (BB), white feathers (WW),
speckled (erminette) feathers (BW) and Cattle: red fur (RR), white(WW), roan(RW)
Many human genes show codominance including one for a protein that controls
cholesterol. People with the heterozygous form of the gene produce two different
forms of the protein, each with a different effect on cholesterol levels.
Problems:
1. Cross a black feather rooster with a white feathered hen.
2. Cross a erminette feathered rooster with a erminette feathered hen.
3. Cross a red haired bull with a white haired cow.
4. Cross a roan bull with a roan cow.