Ara Casta <[EMAIL PROTECTED]> wrote:
Hola!
Reciban un cordial saludo
Me he estado preguntando, c�mo funciona el albinismo
en las orqu�deas?
El albinismo es un accidente en el que participan los
genes de la madre y del padre, pero aunque los dos
sean portadores de ese factor, no todos los hijos
nacen albinos. Tambi�n influye el grado de parentesco
entre los padres. �???????????????????
En realidad no participo, pero leo todos y cada unos
de sus mensajes.
Gracias
Aracelis
Ccas-Venezuela
Aracelis
Caracas-Venezuela
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Genetics - Simple recessive genes in snakes. Co-Dominant/Incomplete Dominant This bit of drivel is intended to create a basic knowledge of herp genetics. In my case I rely on python pattern and color mutations as example. First we need to apply basic genetics to understand color and pattern mutations. We tend to work with numbers that are theoretical expected ratios, the reality of these numbers works better with larger clutch sizes. Smaller clutch sizes often provide disproportional theoretical results. The following punnett square displays the gene pairing of two animals. The "N N" pair denotes the gene pair of alleles of normal appearing animals with no unusual genes. Row 1 is one adult and column 1 is the other adult. #1 Denotes breeding two normals
Denotes the resulting offspring
The resulting offspring are divided into groups of 25%,
when combined they equal the 100% of the clutch. All babies resulting are
A simple recessive mutation - a gene that has proven itself as an inheritable gentic trait. When a visible mutation is bred to a normal appearing non gene carrier the resulting offspring are normal appearing animals that carry the genetics of that mutation. These offspring are known as heterozygous. They carry the genetics of the mutation but visually look normal. Examples of this mutation in ball pythons - Albino, Axanthic, Caramel Albino, Genetic Striped, Clown, Piebald, Ghost are a few. In our case here we shall use the gene of albinism which is a proven simple recessive inheritable gene. To see the gene of albinism at work we are looking for a pair of "a a" which denote an albino. Since albinism is simple recessive we are looking for the lower case pairing. If an upper case "N" occurs it will mask the simple recessive gene. #2 Denotes breeding an albino(a a) row 1 to a normal (NN) column 1
Denotes the resulting offspring
The resulting offspring are all heterozygous gene
carriers(N a) they appear normal but carry the gene for albinism. They are
important and allow breeders the needed "hets" to produce albinos through
selective breeding. #3 Denotes breeding a heterozygous(N a) to a normal (NN)
Resulting offspring
50% of these offspring are normal and 50% are heterozygous albino gene carriers. The resulting babies all appear normal but one out of every two in theory is an albino gene carrier, they are known as 50% possible het albinos. #4 Denotes breeding an heterozygous(N a) to heterozygous (N a)
Resulting offspring
This time we are seeing some results, 25% are normals, 50% are hets and 25% are visible albinos. The normal looking animals consist of heterozygous animals and normals. These normal appearing animals are called 66% possible het albinos since 2/3 of them are actually hets but indistinguishable from normals. #5 Denotes breeding an albino(a a) to a heterozygous (N a)
Resulting offspring
Now we are seeing 50% heterozygous animals and 50% visible albinos without any possible hets. #6 Denotes breeding an albino(a a) to an albino (a a)
Resulting offspring
We are seeing an entire clutch of the simple recessive gene albinism. There are no normal appearing animals. Summary - we have now taken a simple example of
genetics using a known genetic color mutation. This can be replaced by many
other mutations with the same percentages and results. |
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Genetics - Advanced - Double heterozygous genes. This bit of drivel is intended to create a basic knowledge of herp genetics. In my case I rely on python pattern and color mutations as an example. Overview :
The following punnett square displays the gene pairing of two animals. The "N N" pair denotes the gene pair of alleles of normal appearing animals with no unusual genes. Row 1 is one adult and column 1 is the other adult. #1 Denotes breeding two normals
Denotes the resulting offspring
The resulting offspring are divided into groups of 25%,
when combined they equal the 100% of the clutch. All babies resulting are
A simple recessive mutation - a gene that has proven itself as an inheritable gentic trait. When a visible mutation is bred to a normal appearing non gene carrier the resulting offspring are normal appearing animals that carry the genetics of that mutation. These offspring are known as heterozygous. They carry the genetics of the mutation but visually look normal. In our case here we shall use the gene of albinism which is a proven simple recessive inheritable gene. To see the gene of albinism at work we are looking for a pair of "a a" which denote an albino. Since albinism is simple recessive we are looking for the lower case pairing. If an upper case "N" occurs it will mask the simple recessive gene. #2 Denotes breeding an albino(a a) row 1 to a normal (NN) column 1
Denotes the resulting offspring
The resulting offspring are all heterozygous gene
carriers(N a) they appear normal but carry the gene for albinism. They are
important and allow breeders the needed "hets" to produce albinos through
selective breeding. Double Heterozygous genes at play : Breeding two genetic mutations together to Denotes breeding an amelanistic albino(lacking melanin) to an axanthic(lacking brown and yellow).
From this Punnett Square we can see that all the offspring are ax; het for albino and also het for axanthic. We refer to these double hets as het for snow, the resulting albino should lack yellow and appear white. An animal that is het for two genetic characteristics is referred to as a Double Het (DH). Het for albino has one of two possible albino alleles and is more precisely represented as Na. Het for axanthic has one of two possible axanthic alleles and is more precisely represented as Nx. A more precise representation of het for albino and also het for axanthic, therefore, is NaNx. When we breed such a DH animal, it will pass one of the axanthic alleles and one of the albino alleles to its offspring. In passing one of the axanthic alleles either an N or an x will be passed. In passing one of the albino alleles either an N or an a will be passed. The combinations of alleles that can be passed to the offspring, therefore, are as follows: NN - N from axanthic gene, N from albino gene1. Denotes breeding a double het for snow to a normal wild type.
1. Resulting offspring are in theory: 25% normal (NNNN) 2. Denotes breeding two double het snows together.
2. Resulting offspring are in theory out of clutches of 16 animals. Since ball pythons have small clutches the odds of producing a snow ball are 1 in 16. 1 Normal (NNNN) 6.25% of the
clutch. The Breakdown. We take out all of the visible mutations to calculate the remaining genetic odds in the square. We have seven visibles in theory, that leave 9 normal looking animals that have genetic qualities of interest. We take 100 and divide by the number of animals, this equals 11.1% each animal represents in the normal appearing portion of the clutch. The babies of most importance are the double hets., these 4 make up 44% of the clutch. The remaining ratios are 22.2% possible pure het. Albino, 22.2% pure het. Axanthic and 11.1% Normal. This breakdown : there is a 44% chance that any one of the normal appearing animals is a double heterozygous for snow. A 22% chance that any baby is a pure het Albino or het. Axanthic. A remaining 11% chance that the baby is a Normal. Another way to look at is and advertise it : there is a 66% possible chance that a normal looking animal is Het Albino(this includes the het. albino part of the double het.), there is a 66% chance that it is a het axanthic(including het. axanthic double hets.) and a 44% possible chance it is a double het for snow. There will still remain the 11% normal possibility. I hope this helps many people who are trying to get a usable perception of double heterozygous genetics - Kevin. |
