Two dogs with brown fur mate and have a litter of puppies. In the litter, two puppies have golden fur, two puppies have brown fur, and one puppy has black fur. Explain how this is possible.

Here's what I know about this, and I know a lot about dog's U^U

Explanation:

Gregor Mendel was an Austrian monk who, through his scientific work with pea plants, became known as the father of genetics. Mendel illustrated that genes come in pairs with one inherited from each parent. This may sound like a simple gardening experiment, but from pea plants to dogs to humans, genetics is complex.

DNA is not as simple as ABC

The nuclei of dog cells contain important genetic data. The dog has 39 pairs of chromosomes in each cell (39 from the mother and 39 from the father). One of these pairs determines the sex of the dog and the rest determine everything else that makes him or her unique. Chromosomes are made up of thousands of genes that carry traits inscribed in DNA (see article “Understanding DNA” for more information).

"the mother and father each randomly contribute

one allele from each locus, giving each allele a

50% chance of being passed on to the pups."

Genes have pairs of alleles (one from each parent) that are located at specific sites (loci) on a chromosome. When dogs breed, the mother and father each randomly contribute one allele from each locus, giving each allele a 50% chance of being passed on to the pups. One of the alleles at each locus is dominant and determines the traits, like coat color, portrayed in the dog.

It starts with two colors

Despite the huge variety in coat color, there are only two basic pigments that determine the color of canines: eumelanin (black) and phaeomelanin (red). All different variations in color are created by these two pigments, which are both forms of melanin.

"there are only two basic pigments that

determine the color of canines"

Melanocytes are the cells within the hair follicles that add melanin to the hair as it grows and determine basic coat color. The more melanin, the darker the color. The production of melanin is not always at a steady rate so the tip of a dog’s hair may be darker than the rest of the hair shaft.

"Each of the pigments, eumelanin and phaeomelanin,

has a "default" color that can be

modified by various genes."

Each of the pigments, eumelanin and phaeomelanin, has a "default" color that can be modified by various genes. Eumelanin is, by default, black pigment but variation in color occurs because genes modify eumelanin to create other colors such as liver(brown), blue (grey), or isabella (pale brown). Genes essentially “dilute” the pigment into these other colors by preventing the production of full strength eumelanin.

Phaeomelanin is the second pigment that determines canine coat color. This pigment is red with a default color of gold or yellow. Phaeomelanin creates reds that range from deep red (Irish Setter) to orange, cream, gold, yellow or tan. Genes control the intensity of phaeomelanin making the color stronger or weaker. This pigment is produced only in the coat and affects only hair color while eumelanin affects eye and nose color. Phaeomelanin in people is responsible for freckles!

Eumelanin and phaeomelanin in all their forms create a huge range of dog coat colors.  White hair on dogs occurs when cells do not produce any pigment at all. Most of the time this affects certain portions of the dogs coat. For example, you may see a colored dog with white markings. If eumelanin is not produced in the nose, the dog ends up with a pink nose. If eumelanin is absent in the eyes, the dog has blue eyes. Rarely, the entire coat is affected resulting in an albino dog with red eyes.

Genetics expands the range of these two colors.

Many genes impact the color of a dog by manipulating these two basic pigments. The dog genome contains approximately 3 billion base pairs of DNA and thousands of genes. But only 8 genes in the dog are associated with coat color. The loci associated with coat color in dogs are:

A (agouti) locus. This site is responsible for different coat patterns in the dog. Agouti protein controls the release of melanin into the hair and is involved in switching between the two pigments (eumelanin and phaeomelanin).

E (extension) locus. This locus creates the black facial mask of many dogs as well as yellow or red coats. The four alleles of this gene in order of dominance are: melanistic mask (Em), grizzle (Eg), black (E) and red (e).