Cross 7

Purpose: Third backcross to restore the Snow White phenotype

Male (Gandalf):

  • Bought from a big box store during February 2023 as part of the initial stock.

  • Strain: Snow White

  • Relevant genes. Some are assumptions, indicated with italics. Although their decedents strongly support the claims:

    • Base body color: Blond (bb)

    • Magenta: likely homozygous (MM)

    • European Blau: (rr)

    • Stoerzbach: (ss)

Female (C1BF):

  • Gandalf’s daughters from Cross 1 (I used 2 total females).

  • Strain: Half Snow-White

  • Relevant genes. Some are assumptions, indicated with italics. Although their decedents strongly support the claims:

    • Base body color: Gray (Bb)

    • Magenta: likely a carrier (Mm)

    • European Blau: (Rr)

    • Stoerzbach: (Ss)

Offspring:

  • Born: Several Batches between November 2023 and December 2023.

  • Brood Size: 77

    • 18 Male (4 that were juveniles without a clear phenotype)

    • 59 Female (includes a large number of juveniles)

  • Offspring phenotypes and genotypes:

    • The figure above shows all the male phenotypes ordered by the relevant genes that showed an obvious phenotype. Base body color, European Blau, and stoerzbach: I will use the grid as my grouping labels.

    • The females followed a similar phenotype distribution except for stoerzbach. I had a hard time telling apart females that expressed stoerzbach.

    • Genotype distributions. Numbers indicate the distribution with-in just the males excluding the juveniles.

      • A1: Bb|(MM or Mm)|Rr|Ss, 2 males, 11.1%

      • B1: Bb|(MM or Mm)|Rr|ss, 4 males, 22.2%

      • C1: Bb|(MM or Mm)|rr|Ss 0 males, 0%

      • D1: Bb|(MM or Mm)|rr|ss, 1 male, 5.6%

      • A2: bb|(MM or Mm)|Rr|Ss, 1 males, 5.6%

      • B2: bb|(MM or Mm)|Rr|ss, 1 males, 5.6%

      • C2: bb|(MM or Mm)|rr|Ss, 4 males, 22.2%

      • D2: bb|(MM or Mm)|rr|ss, 1 male, 5.6%

    • My expectation was that each of the 8 unique phenotypic combinations (resulting from three genes) would represent roughly 12.5% (indicated by the dotted line) of the offspring. This is because the C1B female is heterozygous for each gene, while Gandalf is homozygous (similar to her C1A sister minus the halfblack gene). This means each individual gene should show an even 50% distribution of its two phenotypes. At first glance, the overall phenotypic distribution seemed skewed towards B1, and C2. However, after examining the distributions of each gene individually, the picture becomes much clearer:

      • Base Body Bolor: 36 Blond : 37 Gray (Both males and females)

      • European Blau (EB): 6 EB : 8 Non-EB (These values reflect males only)

      • Stoerzbach: 7 Stoerzbach : 7 Non-Stoerzbach (These values reflect males only)

      • Note: I did not separate the females of this brood to the same degree as the males. I only started doing this after this brood and cross 6.

  • As anticipated, for genes where C1B is heterozygous and Gandalf is homozygous, we expected a near 50% split between the two phenotypes. And as you can see, the individual gene distributions align remarkably well with this expectation!

Notes:

  • I intentionally didn't focus heavily on magenta gene expression in this cross. The variety of phenotypes already present was extensive, and adding magenta to the analysis would have introduced significant complexity. However, given that magenta is incompletely dominant and Gandalf is likely homozygous (MM) for the gene, all offspring would inherit at least one magenta allele. C1BF, being Gandalf's daughter, is likely heterozygous (Mm) since her mother from Cross 1 (Female #1) probably lacked the magenta gene. Therefore, all offspring in this brood are either MM or Mm. Based on color alone, these phenotypes should be largely indistinguishable. Fin size, however, is a different matter. Magenta is thought to reduce fin size. I believe this largely occurs in its homozygous state, which aligns with its incomplete dominance. While I didn't collect specific fin size data for this brood, I do recall observing both long-finned and short-finned males. Without precise data, a proper distribution analysis isn't possible at this time.

  • I selected three females with a phenotype closest to snow white as breeders for the next cross. These females were paired with the C5BM male from Cross 5, establishing Cross 12. These females were labeled Cross 7 Female A (C7AF).

  • A YouTube video detailing the start of Cross 7 can be found here.