Multiples genes –
three or more forms of a gene for a trait. / Any of a set of three or more alleles, or alternative states of a gene, only two of which can be present in a diploid. That is the sequence of the bases is slightly different in the genes located on the same place of the chromosome.
1. Chinchilla
2. Himalyan (Russian)
3. Albino
4. Skin Colour in Mice
5. Eye Colour in Drosophila
6. ABO blood group system
Polygene -
polygenic inheritance occurs when one characteristic is controlled by two or more genes (usually by many different genes) at different loci on different chromosomes. there is more than one gene involved and their may be multiple alleles of the multiple genes.
1. Human height
2. Kernal color in wheat (5 phenotypic classes)
3. Skin color
Linked genes –
genes on the same chromosome pair. The phenotype ratio for this cross is 3:1.
1. flower color and pollen shape experiment
2. fruit flies eyes color
3. hemophilia
4. red-green colorblindness
Lethal Gene –
a gene that leads to the death of an individual; these can be either dominant or recessive in nature
1. Recessive yellow mouse coat color.
2. Dominant lethal gene - Huntington's disease in humans.
Pleiotropy –
a single gene controls several distinct, and seemingly unrelated, phenotypic effects.
1. human disease PKU (phenylketonuria)
2. sickle-cell anemia
Epitasis –
type of gene interaction in which a gene at one locus masks or suppresses the effects of a gene at a different locus.
1. combs in chicken
2. Flower Color in Peas
