essential question: what is the difference between incomplete and co-dominant traits?
TRANSCRIPT
NOTES: GENETICS
CONTINUED
Essential Question: What is the difference between incomplete and co-dominant traits?
REVIEW FROM GENETICS
- Different forms of a genes are alleles.
- The principal of dominance states that some alleles are dominant and others are recessive.
- Heterozygous genotypes always shows the dominant trait.
WHAT IS INCOMPLETE DOMINANCE?
- Neither allele is dominant in expressing its trait.
- Each allele is represented by a different letter.
- Heterozygous forms will be expressed as a blend of the homozygous traits.
EXAMPLE OF INCOMPLETE DOMINANCE
In some plants the alleles for flower color show incomplete dominance
RR = Red flowers WW = White flowers RW = Pink flowers
PRACTICE PROBLEM Straight hair and curly hair are incomplete dominant and people who are heterozygous have wavy hair.
What are the genotypes for each trait if S is the allele for straight and C is the allele for curly?
Straight CurlyWavy
SS CC SC
Set up the punnett square for a wavy haired woman to marry a curly haired man.
PRACTICE PROBLEM
wavy haired woman: ______ curly haired man: ______
SC
CC
SC
S
C
C C
CC
SC
SC
CC
CC
Based on the Punnet square what percentage of the offspring have:
Straight hair: ______Curly hair: _____Wavy hair: _____
PRACTICE PROBLEM
SC
S
C
C C
CC
SC
SC
CC
CC
0 %50
%50 %
HOW DOES INCOMPLETE DOMINANCE WORK IN HUMANS?
SICKLE CELL ANEMIAHomozygous Dominant (AA) –Normal
Heterozygous (Aa) –Partial Disease
Homozygous Recessive (aa) –Disease
Being heterozygous is a benefit because it protects them from malaria
WHAT IS CODOMINANCE?
- “co”-together (cooperate-work together, cohabitate-live together)
- In the heterozygous form, both traits appear together.
EXAMPLES OF CODOMINANCE
EXAMPLE OF CODOMINANCE IN HUMANS: Blood Types
Humans have 4 blood types: A, B, AB, O
Only 3 alleles: A,B,OAlleles A and B are codominant.
Allele O is recessive.
BLOOD TYPE CHART
Phenotype Genotype
AB
ABO
IAIA or IAIO
IBIB or IBIO
IAIB
IOIO
PRACTICE PROBLEM
Dad has type O and mom has type AB. Set up the punnett square.
Dad genotype = ______ Mom genotype = ______
IOIO
IAIB
IOIO
IAIB
IA IB
IO
IO
IAIO
IAIO
IBIO
IBIO
EXIT TICKET: COPY DOWN AND FILL IN THE
SENTENCE BELOW:
In simple dominance the heterozygous genotype shows the __________ trait. This is different from incomplete and codominance because in incomplete dominance the heterozygous trait shows a ____________ between the dominant and recessive traits, while in codominance ______ traits are show.