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Now, we are going to look at inheritance of 2 genes at the same time. 

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Now, we are going to look at 
inheritance of 2 genes at the same 
time

Example: Rabbit Coat Colour & Ear Length
➜ B – brown coat
➜ b – white coat
➜ E – long ears
➜ e – short ears. 

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Example: Rabbit Coat Colour & Ear Length
➜ B – brown coat
➜ b – white coat
➜ E – long ears
➜ e – short ears

Possible Genotype Combinations
1.
BBEE –
2.
BBee –
3.
BBEe –
4.
BbEE –
5.
Bbee –
6.
BbEe –
7.
-
8.
-
9.
-. 

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Possible Genotype Combinations
1.
BBEE –
2.
BBee –
3.
BBEe –
4.
BbEE –
5.
Bbee –
6.
BbEe –
7.
-
8.
-
9.
-

Worked Example : BbEe X Bbee
Parental phenotypes
Parental genotypes
Parental gametes. 

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Worked Example : BbEe X Bbee
Parental phenotypes
Parental genotypes
Parental gametes

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Another Example: Tomato Plant
stem colour gene
➜ A = allele for purple stem
➜ a = allele for green stem
leaf shape gene
➜ D = allele for cut leaves (jagged edges)
➜ d = allele for potato leaves (smooth edges). 

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Another Example: Tomato Plant
stem colour gene
➜ A = allele for purple stem
➜ a = allele for green stem
leaf shape gene
➜ D = allele for cut leaves (jagged edges)
➜ d = allele for potato leaves (smooth edges)

Question: AaDd X aadd
Parental phenotypes
Parental genotypes
Parental gametes. 

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Question: AaDd X aadd
Parental phenotypes
Parental genotypes
Parental gametes

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The 9:3:3:1 ratio is typical of a dihybrid cross where both parents
are heterozygous at both gene loci. 

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The 9:3:3:1 ratio is typical of a 
dihybrid cross where both parents
are heterozygous at both gene 
loci

Question
In a species of mammal, it is known that the allele for black eyes, B, is dominant to the allele for red eyes, b, and that the allele for long fur, F, is dominant to the allele for short fur, f.
a) What are the possible genotypes for an animal with black eyes and long fur?
a) How could you find out which genotype this animal had?. 

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Question
In a species of mammal, it is known that the allele for black 
eyes, B, is dominant to the allele for red eyes, b, and that 
the allele for long fur, F, is dominant to the allele for short 
fur, f.
a) What are the possible genotypes for an animal with 
black eyes and long fur?
a) How could you find out which genotype this animal 
had?

Dihybrid Inheritance