More Complicated Patterns of Inheritance
Incomplete Dominance
Phenotype of heterozygous is different from homozygous parents
Intermediate btwn two parents
Neither allele is dominant
Carnations
Pure red (RR) x Pure White (rr)
Bright Pink (Rr)
Red (R) is slightly dominate cuz carnations are bright pink not pale pink
Result of F2
1:2:1
R:Rr:rr
Red:Pink:white
Multiple Alleles
Gene that has many different allele forms
One person can only have 2 of these alleles (one of each chromosome of homologous pair)
But, there are many different alleles of that gene in the gene pool
Blood Types
4 Blood Types: A, B, AB, O
Determined by type of antigens found on surface of red blood cells
Type A = antigen A
Type B = antigen B
Type AB = antigen A & B
Type O = neither antigen
Blood phenotype controlled by gene "I"
3 different types of I: IA, IB, i
i = recessive
Genotypes A Antigen B Antigen Phenotype
IAIA + - A
IAi + - A
IBIB - + B
IBi - + B
IAIB + + AB
ii - - O
Complicated Examples
Coat colour in rabbits is controlled by gene C
4 different alleles
Gene that controls production of glucose-6-phosphate dehydrogenase (enzyme)
80 alleles
Co-Dominance
When they have 2 or more dominant alleles
Both dominant alleles are expressed in phenotype
Blood Types
AB
Gene Interaction
Single trait controlled by 2 or more genes acting 2gether
Coat Colour of Labrador Retrievers
2 Genes: B and E
B Gene: 2 alleles
B = Black coat (dominant)
b = Brown (recessive)
E Gene: 2 alleles
E = Golden coat (most dominant)
e = recessive to all genes
Phenotype Possible Genotypes
Golden Coat Eebb or EeBB or EeBb or Eebb or EEBB or EEBb
Black Coat eeBb or eeBB
Brown Coat eebb
Interaction can have many more genes & more complex
Like all cells and organs dependent on each other
Genes rarely act on their own
Genes that control flower colour depend on gene that controls flower production
Traits that show Continuous Range of Phenotypes
Instead of 2 or 3 distinct form
Height
Results from many genes acting upon each other in different parts of body
Environment is also important
Cells can't reproduce w/o enuf nutrients
English: Trio Combination 2: Biological Mother and...
Icelandic sheep, two colors, taken in Iceland, Jun...
Category:Medical genetics images (Original text : ...