Warm up
• Complete the punnet square for a Tall pea
plant. T= tall t=short.
– The parents are Tt x tt
– What are the genotypes and phenotypes?
– What are the genotype and phenotype ratios?
Types of Inheritances
Pp 237, 242-245
Types of Inheritance
•
•
•
•
•
•
Complete Dominance
Incomplete Dominance
Codominance
Sex-linked
Polygenic
Epistasis
You will be
responsible to
complete punnett
squares for the
types bolded
Complete Dominance
•
•
•
•
One allele is completely dominant over the other
Only two phenotypes exist
One phenotype is masked
The heterozygous phenotype shows dominant trait
–
–
–
–
Ex: Tall peas are dominant to short peas
TT= tall
Tt= tall
tt=short
Complete Dominance
Autosomal Genetic Disorders.
Carrier: A heterozygote for a recessive disorder
(ex/ Cc).
• Carrier does not show symptoms but can pass
recessive allele to offspring
• Affected person must inherit two recessive alleles
• Example Cystic Fibrosis, Tay-sachs, sickle-cell
anemia
• CC &Cc = unaffected
• cc = affected
Incomplete Dominance
• Neither allele is completely dominant over the
other
Incomplete Dominance
• Neither allele is completely
dominant over the other
• Three phenotypes exist
• The heterozygous phenotype
shows blended trait
Incomplete Dominance
• Neither allele is completely dominant over the
other
• Three phenotypes exist
• The heterozygous phenotype shows blended
trait
• Ex: Flowers can be pink, red, or white.
– RR=red
– rr= white
– Rr=pink
Incomplete Dominance
• Cross two pink flowers
– Draw Punnet Square
• What percent of their offspring will have white
flowers?
Incomplete Dominance
• Cross two pink flowers
• What percent of their offspring will have white
flowers?
• Fish can be green (GG), blue (BB), or teal
(GB)
Green (GG)
Teal (GB)
Blue (BB)
Codominance
•
•
•
•
Both alleles are dominant
Three phenotypes exist
Neither phenotype is masked
The heterozygous phenotype shows both traits
at once
Codominance
•
•
•
•
Both alleles are dominant
Three phenotypes exist
Neither phentoype is masked
The heterozygous phenotype shows both traits
at once.
X
red (RR)
=
white (WW)
Codominance
•
•
•
•
Both alleles are dominant
Three phenotypes exist
Neither phentoype is masked
The heterozygous phenotype shows both traits
at once. (Not a blend)
X
red (RR)
=
white (WW)
red & white(WR)
Codominance
EX: In Smileys, eye shape can be starred,
circular, or a circle with a star.
Write ALL the phenotypes and genotypes that
exist.
Codominance
EX: In Smileys, eye shape can be starred,
circular, or a circle with a star.
Write ALL the phenotypes and genotypes that
exist.
• CC = circle
SS = star
SC = circle-star
Homework
• Incomplete Dominance WS
– 3 pages
– Must be colored for credit.
Single gene traits
• controlled by only one gene
- complete, incomplete, and codominant
EX. Huntington Disease (D/d), Sickle Cell
Anemia (N/S) , Cystic Fibrosis (R/r)
Polygenic traits
• controlled by additive effects of two or more
genes
EX. Skin color (controlled by 3-6 genes), eye
color
- each gene is responsible for adding
pigment
Multiple allele trait
• controlled by more than two
alleles in one gene
• Still only inherit one copy from
each parent for a total of two
alleles but have a few to
combine
EX. Blood type:
IAIA, IAi , IBIB , IBi , IAIB, ii
Blood Typing
Trait controlled by multiple alleles, with two that
are codominant and one “null”
Dominant Allele: I
2 Dominant Alleles:
A: IA B:IB
Recessive Allele: i
1 Recessive Allele:
O= i
• Trait controlled by multiple alleles, with two
that are codominant and one “null”
• Someone with AB blood can receive blood
from A, B, AB, and O because it doesn’t have
antibodies to clump cells. However it can only
be giving to AB because all other blood types
have antibodies that can cause clumping with
the AB cell.
• Use serums that contain these antibodies to test
blood type
Sex linked traits
• Gender determined by XX or XY
• Disorder/trait found on the “X” chromosome
• seen more in men than women
EX. (color blindness and hemophilia)
• “Y” has to come from father
• “XR or Xr” vs just “R or r”
XR
Y
• Possible genotypes and phenotypes:
XR XR = normal vision
XR Xr = normal vision
XR
Xr
Xr Xr = color blind
XR Y = normal vision
XRY XrY
Xr Y = color blind
XRXR XRXr
Sex-influenced trait
• Usually autosomal
• Specific hormones influence trait/genotype
EX. Baldness: testosterone influences BB
Rh factor
• people who are Rh+ have Rh antigens the red
blood cell's surface
• A person with Rh- blood has Rh antibodies in
the blood plasma that react with the Rh+ blood
antigens
Testing Blood Type
• Use anti-A serum and anti-B serum
• If you use anti-A serum and it clumps then it
has A antigens (proteins), if you use anti-B
serum and it clumps then it has B antigens
• No clumping = no antigens
What blood type would this be?
Homework
• Read 237 -242
• Problems p 240 #1-6
• P 251 # 1, 4, 5, 6