|© The Orca Ocean|
|When some people find out there has been a whie orca they are stunned. White whales are ususally something reserved for a Melville novel. However, white whales are not all that uncommon, and no I am not speaking of just belugas. There are many whales that have white offspring: Sperm whales, humpbacks, right whales, and others. But how is this possible? One word: Genetics.|
|No Albino Calf Born X
With the above punnett square mapped out, it can be seen that the two parent orcas could not be both homozygous dominant because there are no mutant genotypes (aa) present.
|No Albino Calf Born X
With the above punnett square mapped out, it can be seen that the parents cannot be homozygous dominant and heterozygous for there are no mutant genotypes (aa) present.
|Albino Calf Possible!
With the above punnett square mapped out, it can be seen that the two parent orcas of the albino calf had to be heterozygous. This is the only way the white calf could have been born.
|So the possibility of an orca, or any other cetacean, being born white is good. There have been many cases of them having been born so, but what is the probability? Since the punnette squares have mapped out which of the three possibilities given to us (there would have been five, but remember we have already pointed out both of Chimo's parents were normal-colored (wildtype) orcas, so we do not have to perform the AA x aa or Aa x aa crossings) is the correct one to go with, we can map out the mating of the parent orcas and find the probability of the orca calf being born white.|
| As seen in the pedigree mapping to the left, there is a 1/4 chance of the calf of the two normal orcas with a heterozygous genotype producing an albino calf. If you look at the punnette square above on the right, two of the possible four progeny will be heterozygous, one will be homozygous dominant, and the other one will be homozygous recessive. Therefore, there will be a 25% chance (1/4) that any orca born from this mother and father will be born white.
*A note about the pedigree to the left. The squares sybolize a male, the circles sybolize a female. The colored in shape is the individual that will be albino and be aa. The dots within the shapes normally symbolize when the individual is a carrier, NOT heterozygous, however to make this simple I have placed a dot within the shapes to show who is heterozugous, who is homozygous recessive (colored in shape), and who is homozygous dominant (white shape).
| As you may have noticed in the image above, there was a female killer whale (Chimo) born who was nearly all white; save for some scars and a few patches where black would normally be and was simply muted to gray. But how come there was a white orca? And if it is true, how come there were two? Genetics. To understand this you do not need to be a geneticist or have a college degree in a scientific or medical field.
To start out with, we will define a few terms and set up some assumptions.
Genotype: What the gene looks like (i.e. AA, Aa, aa)
Phenotype: The outside appearance of the gene (i.e. hair colors, eye color, etc)
Wildtype: The normal gene (in our case, the gene that causes the orca to be black and white).
Mutant: The gene that is mutated (in our case, the gene that causes the orca to be just white). Genes are named for the mutant.
Homozygous Dominant: Having two alleles that are the same on the gene and are dominant (AA).
Homozygous Recessive: Having two alleles that are the same on the gene and are recessive (aa).
Heterozygous: Having one of each allele on the same gene, one dominant and one recessive. This still shows the dominant trait (Aa).
Carrier: An organism that carries the potential for a specific mutation, but does not show it themselves.
Let's really begin! The wildtype alleles in the gene for albinism is either AA or Aa. The mutant genotype of albinism is represented as aa. The homozygous recessive genotype (aa) is the gene that will express the phenotype of albinism. To be a white orca, such as Chimo, there needs to be that gene with those two alleles. Since Chimo was the only white orca reported (other than Alice who shares Chimo's mother [see Chimo's page for details]), then it is assumed her father was of wildtype coloring as was her mother. If that is so, how can two normal orcas have a white calf? The illustration below explains: