Angelfish Genetics

Punnett Square: This is particularly useful when first learning about angelfish genetics and how to identify the outcome of a monohybrid cross. It is recommended that you use this until you are very comfortable with how alleles are donated by each angelfish parent. Place the alleles of one parent across the top and the alleles of the other parent on the side. Then bring each allele down or across to the box in its row or column. Each box represents the possible outcome of each cross. This represents the genotype of each angelfish. The phenotype (how it looks) is determined by the dominant and recessive characteristics of each allele in its respective box. In the example below, each box represents 25% of the total spawn. Therefore, 25% of the spawn will be true breeding Double Dark Black angelfish (DD), 50% will be hybrid Black angelfish (Dg or gD) and 25% will be true breeding Gold angelfish (gg).

Branch Diagram: When dealing with multiple traits, it is much less complex to consider the genetic interaction of these traits separately, and then combine the results using a branch diagram.

Test Cross: There is a simple method used to distinguish the genotype of of an angelfish with an unknown genetic inheritance. The angelfish of unknown genotype is crossed to a homozygous recessive individual.  For example, you have a dark angelfish that shows streaking in the fins and you want to determine its genotype.
Test cross: Cross this dark angelfish into a homozygous recessive gold angelfish (gg) that is a proven to have no other hidden mutations. Let's say the resulting (F1) shows 50% gold (gg) and 50% dark angelfish. Of the dark angelfish, 50% are streaked, as the one parent. The other dark angelfish appear as normal blacks.
Analysis: All of the F1's received a Gold allele from the Gold parent. The 50% gold fry means that the dark parent also contained the allele for Gold. The dark F1's without streaking, proves that a Dark allele (D) was donated by the dark adult angelfish.  This means the dark parent has two identified alleles at this point - (D and g). Since Dark and Gold are alleles, we now know that the gene that causes streaking is not an allele of  Dark. The dark angelfish parent could not have 3 alleles on one locus. Because the original gold did not contain the allele that causes streaking (came from dark parents that showed no streaking), we know that the streaking in the F1's came from the dark parent. 50% streaked dark F1's is consistent with a dominant allele that causes streaking and shows that the original dark parent was heterozygous for this trait.  The original angelfish parent is proven to be heterozygous for  Dark, Gold  and Streaked (D/g-St/+).

Variety: Any of a group of widely separated variants within a single interbreeding population. As used within the hobby, varieties of angelfish include the different color types, i.e., Black, Gold, Marble, etc..

Strain: The descendants of a common group within a variety. I may be working on a strain of Koi angelfish that exhibits bright orange on most of the body and a yellow eye. Another breeder may have a different strain of Koi angelfish that exhibits yellow on the body and a red eye. They are both the same variety, but a different strain of that variety.

Line: The descendants of a common ancestor within a strain. For example, I decide to set up four separate lines within my strain of orange bodied, yellow eyed Koi angelfish. Each line is kept separate and periodically out-crossed to another of the four lines to create a new line. The use of lines helps to keep the immune system strong, while maintaining the same strain within the same variety.

Inbreeding: A breeding technique to fix traits known to a particular line of angelfish. This involves the mating of closely related angelfish, i.e. brother to sister, father to daughter. A strain's immune system is deteriorated using this method. With this technique you can also more easily identify recessive traits, both good and bad.

Line-breeding: A breeding technique for developing the positive attributes of a strain. This involves the mating of angelfish that are related, i.e. brother to grandmother, father to cousin, etc.. Separate lines are kept that are crossed to each other every 3rd or 4th generation. This is a more forgiving system then inbreeding, but care must be taken, because the immune system is still compromised, though to a lesser degree.

Out-crossing: A breeding technique of using unrelated parents. It can strengthen the immune system and it can be used  to bring in desirable traits the current line does not have. Out-crossing can make it difficult to "fix" a characteristic and can also introduce hidden undesirable recessive traits to the line.

F1 Generation: F1 is the symbol given to the first filial generation of progeny from a cross of non-siblings. This cross is represented by (P1 x P2 = F1). When representing a cross, you use parent (P) to indicate the original  breeders. You can only get to an F2 by breeding siblings (F1 x F1 = F2). If you cross back to a grandparent, the resulting fry are also F1's, because it would be represented the same way as the first example (P1 xP2 = F1).

The reason you want to track it in this manner, is so you will know whenever a different gene pool has been added to the line. When trying to fix certain traits, rather than strict inbreeding, you may want to start different lines that will be inbred and then crossed to each other every 3rd or 4th generation. You would then probably want to change to a different labeling scheme. I would suggest lowercase letters to represent each line, to avoid confusion with the generation numbers. Adult angelfish would be labeled as follows: Line (a) = (aP), line (b) = (bP), line (c) = (cP), etc. This way, you can track this modified form of inbreeding. (aP1 x aP1 = aF2), (aP3 x bP3 = aF1). Let's say you linebreed for another 10 generations and then decide to bring in other unrelated stock and cross it into Line 1. You will want to label the new line so you know it's unrelated. (aP3 x eP1(new) = aF1), or if you decide to keep line (a) and create a new line (e), it would be (aP3 x eP1 = eF1).

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