Transcript Beyond Dominant and Recessive

Beyond Dominant
and Recessive
Non-Mendelian Inheritance
Chapter 10-3 (eye book)
This means traits that don’t
fit Mendel’s patterns of
inheritance
?
Co - Dominance
• In co dominance, there are three phenotypes.
• For this type of inheritance, there are two dominant
traits.
• This time, both dominant traits show in the
heterozygous phenotype
– For example: The two dominant traits of this type of fowl are white and
black. The heterozygous phenotype appears speckled
Co Dominance
• The way we write alleles for this type of
inheritance is with two different capital letters.
• Each dominant trait gets its own letter
• The heterozygous genotype gets both capital
letters
Red = RR
Stripes = RW
White = WW
Practice
1. Look at all the cows. What are all the phenotypes?
2. Which two traits are dominant, which is the mixed
trait?
3. What notation will you use to represent…
a) The brown cow?
BB
b) The white cow?
WW
c) The speckled?
BW
Incomplete Dominance
(Also called – Intermediate inheritance)
• In incomplete dominance, there are three
phenotypes. The heterozygous phenotype is
halfway in between the two other phenotypes
• This is referred to as blending
Incomplete Dominance
(Also called – Intermediate inheritance)
• Since one phenotype is not dominant over
the other, the homozygous phenotypes
are both considered dominant.
Red = Dominant
Pink = Blended
White = Dominant
Incomplete Dominance
(Also called – Intermediate inheritance)
• The way we write alleles for this type of inheritance is
with letters and superscripts.
• We pick one letter to represent the trait
– (ex – C for color)
• We use superscripts to represent the expression of
the trait
– (ex – two different capital letters, for each dominant trait)
Red = CRCR
Pink = CRCW
White = CWCW
Practice
1. Look at all the fish. What are all the phenotypes?
2. Which two traits are dominant, which is the
blended trait?
3. What notation will you use to represent…
a) The blue fish?
b) The red fish?
c) The purple fish?
CBCB
CR CR
CR C B
Lethal Allele
When an organism with a particular genotype
does not survive
Example: Mexican Hairless Dogs
H
H
h
HH
Hh
h
Hh
hh
Dogs with the genotype HH do not develop and are never
born. The resulting phenotype ratio is 2 hairless : 1 with hair
Lethal Allele
• This is like Mendelian genetics
because:
– There are only two phenotypes
– We use the same letter in capital
and lower case
• This is different than
Mendelian genetics because:
– You never get a 3:1 ratio – you
get a 2:1 ratio instead
Multiple Alleles
•Some traits have more than two
possible alleles.
•Organisms still get two alleles, one
from each parent
•This increases the number of
possible genotypes and phenotypes
Multiple Alleles
• Human blood type is
a good example of a
trait with multiple
alleles.
• There are 4 different
blood types: A, B, AB
or O, which refer to a
specific carbohydrate
on the red blood cells
Phenotype
(Blood type)
Genotype
O
IOIO
A
IAIA or IAIO
B
IBIB or IBIO
AB
IAIB
Copy this flowchart into
your notes!!!
3 phenotypes
2 phenotypes
2:1 ratio
Lethal
Start
All other
ratios
Mendelian
Blending
Incomplete
Dominance
Both traits
show
Codominance
White Horses
Brown Horses
1. What type of inheritance is shown?
Tan
Horses
2. What gene symbols (letters) should you use to represent
each phenotype?
3. What parent cross led to this population?
Prove it with a Punnett Square
All Tan
Horses
Tan
puppies
Brindle (striped tan
and brown) puppies
brown
puppies
1. What type of inheritance is shown?
2. What gene symbols (letters) should you use to represent
each phenotype?
3. What parent cross led to this population?
Prove it with a Punnett Square
Half tan puppies and
half brindle puppies
More Practice
A) 100% white fish
B) 100% red fish
1. Mode of Inheritance
2. Gene Symbol (Letters) for each phenotype
3. Parent cross that gave us population A)
B)
C)
C) 66% red fish &
33% white fish
Population 1 –
100% White fish
Warm Up
Population 3 –
50% Red fish and
50% striped fish
Population 2 –
100% Striped fish
1. What type of inheritance is shown? all three have the same:
( Mendelian / Incomplete dominance / Co-dominance / Lethal)
(Use your flow chart from yesterday to find out!!!)
2. What are the three phenotypes present?
(Look at the fish, and write down the three types you see)
3. What gene symbols (letters) should you use to represent
each phenotype?
(Use your notes from yesterday to find out!!!)
4. What are the genotypes of the fish in each population?
(Match your answer from #3 to each population of fish)
MOI Table:
• Mendelian and Lethal Parental Crosses:
RR x RR
Rr x Rr
RR x Rr
Rr x rr
RR x rr
rr x rr
• Non Mendelian Parental Crosses:
RR x RR
RW x RW
RR x RW
RW x WW
RR x WW
WW x WW
CWCW x CWCW
CWCR x CWCR
CWCW x CWCR,
CWCR X CRCR
CWCW x CRCR
CRCR X CRCR
NOTE – All Examples are for Red and White…you can use ANY letters