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FELINE DISEASES
Autosomal Inheritance
When cats breed they each contribute half of their genes at random to their offspring. For autosomal genetics the gene is either dominant or recessive. If a condition an autosomal dominant trait only one of the dominant genes is required from either parent for the condition to appear in the offspring. Autosomal recessive conditions require both of the parents to contribute a recessive gene for the condition to appear in the offspring. For this case think of (N) as being a dominant gene for extra toes and (n) as being the recessive gene.
The possible outcomes of breeding are outlined below:
A) Both parents have a pair of dominant genes (N and N). When both genes are the same, either recessive or dominant this is called homozygous. Where one recessive and one dominant are present the gene is heterozygous in that animal
TOM CAT
N--------------N
Q
U N 1.NN 2.NN
E
E N 3.NN 4.NN
N
All offspring (1,2,3,4) will have exactly the same genetics as their parents. If the condition was autosomal dominant both parents would have extra toes and 100% of the offspring will have extra toes. If the condition was autosomal recessive none of the parents or offspring would be affected.
- One parent (either Tom or Queen) has a mixture of the dominant and recessive genes (N and n) and the other has both dominant genes (N and N). If the condition is autosomal dominant both parents will have extra toes whereas with an autosomal recessive condition neither parent would have extra toes.
TOM CAT
N--------------n
Q
U N 1.NN 2.Nn
E
E N 3.NN 4.Nn
N
In this case offspring 1 and 3 would be exactly the same as the queen, with two dominant genes. Offspring 2 and 4 would be exactly the same as the Tom, with a dominant and recessive gene. The Tom cat and offspring 2 and 4 would be called carriers because although they don’t show the effects of the recessive gene they have they nonetheless have it and can pass it along through subsequent generations. In an autosomal recessive condition 50% becomes carriers, but none the offspring would have extra digits. With an autosomal dominant condition all the offspring would be affected.
- Both parents are carriers, with a dominant and recessive gene each (N and n)
TOM CAT
N-----------------n
Q
U N 1.NN 2.Nn
E
E n 3.Nn 4.nn
N
Offspring 1 has both dominant genes. Offspring 2 and 3 would be the same as both parents. Offspring number 4 has both recessive genes. In an autosomal dominant condition offspring 1,2,and 3 would have extra toes while offspring 4 would be normal. Offspring 1 would always produce kittens with extra toes if used for breeding. If the condition was autosomal recessive 2 and 3 would be carriers without showing signs. Offspring 1 would be normal while 4 would have extra toes.
- One Parent has both recessive genes (n and n) and the other parent has both dominant genes (N and N).
TOM CAT
n -----------------n
Q
U N 1.Nn 2.Nn
E
N
In this case all the offspring would be carriers and they would all have extra toes if the condition was dominant whereas none would be affected is the condition was recessive..
- Both parents have both recessive genes (n and n)
TOM CAT
n ---------------n
Q
U n 1.nn 2.nn
E
E n 3.nn 4.nn
N
All offspring would have only the recessive genes and therefore would all be normal if the condition was dominant, with no extra toes. Equally all offspring would have extra toes in a recessive condition.
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