The Grey Calico Cat: A Dilute Wonder

 

grey calico cat?

A grey calico cat is a type of coat color and pattern which consists of grey and cream markings on a white background. This unusual combination is the dilute form of the more traditional black, red and white calico.

Grey calicos owe their paler colours to the dilute gene which, as the name suggests, dilutes the full-color version.

Black becomes grey (blue)

 Red becomes cream

 Chocolate becomes lilac (lavender)**

 Light brown becomes fawn

What is dilution?

The cat inherits two copies (versions) of each gene (known as alleles), one from each parent. A gene can be dominant or recessive. If each copy is different, the dominant gene will be expressed over the other. The cat must inherit two copies of a non-dominant gene for it to be expressed.

Dilution is due to a single base deletion 1 bp in the melanophilin (MLPH) gene which provides instructions for making melanophilin, a carrier protein that is found in the pigment-producing melanocytes. This protein is essential for the even distribution, transport, and translocation of pigment granules. Menalocytes are specialised cells that contain organelles known as melosomes. Melanosomes synthesise, store and transport melanin out of the cell via the dendrites to neighbouring keratinocytes (keratin producing cells).

n the dilute cat, melanin synthesis is normal, but the pigment granules are enlarged and deposited into the hair shaft unevenly, some areas will contain clumps of pigment granules while other parts of the hair contain none.

Melanocyte
Mode of inheritance

The dilute gene is autosomal recessive to non-dilute (dense color), this means the cat must inherit two copies of the dilute gene (one from each parent) to show the dilute coat color.

Dense|Dilute

---|---

Black| Blue (silver)

Chocolate (brown)|Lilac

Cinnamon|Fawn

Red |Cream

Genotypes

DD (Heterozygous – Full color)– The DD cat is full color and cannot pass on a copy of the dilute (d) gene to offspring.

Dd (Homozygous – Full color, carries dilute)– The Dd cat is full color, but has one copy of the dilute (d) gene.

dd (Heterozygous – Dilute) – The dd cat is dilute but can produce full-color kittens if it mates with a cat carrying at least one copy of the dense (D) gene.

3 outcomes between different matings:

The Punnett squares below show what would happen between different matings with an average litter of four kittens.

Phenotype: Both parents are dense.

Genotype: Both parents carry two copies of the dense gene (homozygous). DD x DD.

Punnett square

Outcome:All offspring are homozygous for dense, and cannot pass on the dilute gene.

Phenotype: Both parents are dense.

Genotype: One parent carries two copies of the dense gene (homozygous), and one parent carries one copy of the dense gene and one copy of the dilute gene. DD x Dd.

Punnett square

Outcome: All offspring are dense, two are homozygous and cannot pass on the dilute gene, two carry the dilute gene, which they can pass on if they mate with a cat who also carries the dilute gene. DD, Dd.

Phenotype: Both parents are homozygous dilute.

Genotype:  Both parents are homozygous dilute. dd x dd.

Punnett square

Outcome: All offspring will are dilute. dd.

Phenotype:

Both parents are dense, but carry one copy of the dense gene, and one copy of the dilute gene (heterozygous).

Genotype:

Both parents are heterozygous, carrying one copy of the dense gene and one copy of the dilute gene. Dd x Dd.

Punnett square

Outcome:

One kitten is homozygous dense, two kittens are heterozygous dense and carry the dilute gene, and one kitten is homozygous dilute. DD, Dd, dd.

Phenotype:

 One parent is dense and one parent is dilute.

Genotype:

 One parent is dense, carrying dilute and one parent is dilute. Dd x dd.

Punnett square

Out come 

Two kittens are dense but carry