Transcript RR Rr

How do we get blended traits?

Incomplete dominance
________________________The
dominant allele will not fully cover up
a recessive allele and the trait will be
a result of the two blending or mixing
together.
How do we get blended traits?

In carnations, incomplete dominance can be seen
in flower color:
 red

r
white (rr)
1. Cross two pink carnations
______x______
Rr
Rr
R
R
(RR) pink (Rr)
r
RR
Rr
Rr
rr
A. Possible genotypes of offspring:
RR= ¼
Rr= 2/4
Rr=1/4
B. Possible phenotypes of offspring:
Red= ¼
Pink= 2/4
White= ¼
How do we get blended traits?
2. Cross a red and a pink carnation:
RR
Rr
_______x_______
A. Possible genotypes of offspring:
RR: 2/4
Rr: 2/4
R
R
R
RR
RR
r
Rr
Rr
B. Possible phenotypes of offspring:
Red: 2/4
Pink: 2/4
Practice Problems: Incomplete
Dominance- pg. 4
In humans, hair texture is due to
an incompletely dominant trait.
Straight hair (H) is incompletely
dominant to curly hair (h). When
crossed, they produce a
heterozygous individual with
wavy hair (Hh).


List all possible phenotypes and the corresponding genotype
for hair texture.
Straight (HH), Wavy (Hh), and Curly (hh)
_______________________________________
Practice Problems: Incomplete
Dominance- pg.4

Using a Punnett square, cross a curly-haired
person with a wavy-haired person.
hh
Hh
_______________
X __________________
Show your lists of genotypes & phenotypes here!!!
h
H
h
Hh
hh
h
Hh
hh
HH: 0/4
Hh: 2/4
hh: 2/4
Straight: 0/4
Wavy: 2/4
Curly: 2/4
0:2:2
What is the genotypic ratio of the offspring? ________________________
0:2:2
What is the phenotypic ratio of the offspring? _______________________
Practice Problems: Incomplete
Dominance pg.4
In guinea pigs, white fur (F) is incompletely dominant
over yellow fur (f). When crossed they produce
heterozygous offspring with cream-colored fur (Ff).
 List all possible phenotypes and the corresponding
genotype for fur color.
White: FF Cream: Ff yellow:ff
_______________________________

Practice Problems: Incomplete
Dominance pg.4
• Using a Punnet Square, cross two guinea pigs with cream-colored hair.
Ff
_______________
X __________________
Show your lists of genotypes & phenotypes here!
F
f
F FF
Ff
f Ff
ff
Genotypes:
FF: ¼
Ff: 2/4
ff: ¼
Phenotypes:
White: ¼
Cream: 2/4
Yellow: ¼
What is the genotypic ratio of the offspring?
1:2:1
________________________
What is the phenotypic ratio of the offspring?
_______________________
Can we express 2 traits at once?
Pg. 5

Codominance - When two different
equally , at
alleles are expressed __________
the same time (neither one is recessive).
Can we express 2 traits at once?
Pg.5


Codominant alleles are written as capital letters with
superscripts or subscripts (HR or B1). Since the trait is
inherited from both parents, it is important to still use two
‘sets of letters’ as seen below:
The allele for red hair (HR) is codominant with the allele
for white hair (HW) in cattle. Cattle that have the
genotypes HRHW are called roan because their hair is a
mixture of red and white hairs.
Can we express 2 traits at once?
HRHR = Red
HRHW = roan
HWHW = White
Cross a red cow and a white bull:
HR
HW
HR
HRHW
HRHW
HW HRHW
HRHW
1. Possible genotypes of offspring:
HRHR : 0/4
HRHW: 4/4
HWHW:
0/4
Genotypic Ratio:
0:4:0
2. Possible phenotypes of offspring:
Red: 0
Roan: 4
White: 0
Phenotypic Ratio:
0:4:0
Can we express 2 traits at once?


HRHR = Red
HRHW = roan
HWHW = White
Cross a roan cow and a roan bull:
HR
HR
HRHR
HW
HRHW
A. Possible genotypes of offspring:
HRHR: 1/4
Genotypic Ratio:
HRHW: 2/4
1:2:1
HWHW:
1/4
HW
HRHW
HWHW
B. Possible phenotypes of offspring:
Red: 1/4
Phenotypic Ratio:
Roan: 2/4
1:2:1
White: 1/4
What are some examples of
Codominance in humans?

In humans, red blood cells contain a protein
called hemoglobin. It is the hemoglobin that
gives the red blood cell its color and ability to
pick up oxygen and carry to other cells.
What is Sickle Cell Anemia?

https://www.youtube.com/watch?v=Qd0HrY2NlwY
How is sickle cell anemia inherited?

Sickle cell _________
sufferers are homozygous
(HSHS)
 Because
all of their blood cells are affected by the
sickle cell gene, these people are severely afflicted
by the disease. Their red blood cells can becomes
sickle shaped, rigid and live about 20 days. They
also tend to get stuck in narrow blood vessels, which
may cause complications.
How is sickle cell anemia inherited?

carriers are heterozygous
Sickle cell ___________
(HAHS)
 These
carriers produce normal blood cells and
sickle cell blood cells. Usually these people do not
experience severe affects of this disease.
Sickle cell anemia is more
common in some parts of the
world because being a carrier
causes Malaria resistant. In
places where Malaria is a
problem, having 1 copy of the
sickle cell gene is beneficial.
How is sickle cell anemia inherited?

normal hemoglobin (no sickle
Cells with _________
cell anemia) are homozygous (HAHA)
 Their
red blood cells are disk shaped, soft/flexible
and live for about 120 days.
How is sickle cell anemia inherited?


Complete a punnett square to determine the
chances of two sickle cell carriers having a
homozygous normal child?
AHS
A HS
H
H
Genotype of parents: ________ x ___________
HA
HA
HS
HAHA HAHS
HS HAHS HSHS
HAHA: ¼ Normal
HAHS: 2/4 Carriers
HSHS: ¼ Sufferer
25%
Practice Problems: Codominance
pg. 7

In horses, pale cream color (C) is codominant to
chestnut color (C). When crossed, they produce a
heterozygous individual called a palomino (C C)
which has a cream & chestnut coat.
List all possible phenotypes and the corresponding genotype for
coat color.
Pale
(CC) Palomino (CC’) Chesnut (C’C’)
___________________________________________
Practice Problems: Codominance
pg. 7

Using a Punnett square, cross a palomino horse with
another palomino horse.
C C’
C CC CC’
CC’ C’C’
C’
CC’
______x_______
Show your lists of genotypes & phenotypes here!
CC= ¼ Pale
CC’= 2/4 Palomino
C’C’= ¼ Chesnut
1:2:1
What is the genotypic ratio of the offspring? _______
1:2:1
What is the phenotypic ratio of the offspring? ______
Practice Problems: Codominance
pg. 7


In chickens, black feather color (FB) is codominant to
white feather color (FW). The heterozygous
individual is a combination of black and white
feathers that results in a checkered pattern (FBFW).
List all possible phenotypes and the corresponding genotype
for feather color.
Black
(FB FB ), Checkered (FBFW) White (FWFW )
_________________________________________

Practice Problems: Codominance
pg. 7

Using a Punnett square, cross a checkered chicken
with a black chicken.
FB
FW
FB FB FB FBFW
FB FB F B FB FW
_____x_____
FB FW FB FB
Show your lists of genotypes & phenotypes here!
FB FB : 2/4 Black
FBFW: 2/4 Checkered
FWFW: 0/4 White
2:2:0
What is the genotypic ratio of the offspring? _________
2:2:0
What is the phenotypic ratio of the offspring? _________