COMPLEX PATTERNS OF INHERITANCEPatterns of inheritance that do NOT follow Mendels law.
Review Mendels Simple GeneticsThere are 2 alleles for each trait.An allele is either Dominant Which is represented by upper case, D.The phenotype is visible w/just one allele.So the phenotype is visible with either a heterozygous or a homozygous genotype.Or RecessiveWhich is represented by lower case, d.The phenotype is visible ONLY w/2 recessive alleles: thats the homozygous recessive genotype.
Review Mendels Simple GeneticsMendels Law of Segregation: these alleles will separate from each other during the formation of gametes.
Mendels law of Independent Assortment: theses alleles will be assorted into the newly formed gametes independently of each other.
Incomplete DominanceThe phenotype of the heterozygote is in between those of the two homozygotes.
It is an intermediate, and a third phenotype appears when the heterozygote is present
In heterozygotes, neither allele is completely dominant.
Example-SnapdragonsRR = RedRR = WhiteRR = Pink R RR
CODOMINANCEThe phenotypes of both alleles are equally expressed in the heterozygote.
HRHR = Red Horse
HWHW = White Horse
HRHW = Roan Horse
Multiple AllelesTraits controlled by more than 2 alleles (more than 2 phenotypes)
A diploid individual can only have 2 alleles of a trait.
Example: Blood type = 3 different alleles: IA, IB, i
Blood TypeBlood Type That Can Be ReceivedType of Antigens PresentType of Antibodies ProducedA ( IA )A and OA antigensB antibodiesB ( IB )B and OB antigensA antibodiesO ( i )Universal DonorOnly ONo antigensA and B antibodiesAB ( IAIB ) Universal RecipientAll typesA and B antigensNo antibodies
HRGenes can be on the same chromosome or on different chromosomes.
Phenotypes usually show a continuous range or variability.
- Example: Height = A, B, and C all contribute to height.
AaC cBbTallest = AABBCC
Shortest = aabbcc
In between = AbBbCc
Polygenic traits include: skin color, body weight, eye color, hair color, and height.Polygenic traits