Rat Genetic Code Basic Explanation

Rattie Rascals Rattery
Port Orchard, WA
Est. 1998
(360) 876-0236 day - (360) 874-9085 evening
Rattie@boardmanweb.com
Owned and operated by
LeAnn & Beth Boardman

Rat Genetics
Basic Explanation of How to Read and Use Genetic Codes

1. Each rat carries genes. They pass on one copy of each gene type to their offspring.

2. All rats are either:
aa – black (non-agouti)

A/ - agouti (Wild Type)

They carry these traits regardless of what they express (look like)

3. Coloring is expressed due to the extra color genes or eye dilutions the parents pass onto their offspring. These color genes are shown by letter symbols.

A capital letter such as A for agouti means it is a dominant color gene. When you see A/- it means the other gene has not been identified as an A (agouti) or a (black).
Aa=agouti
AA=agouti
aa=black
Two copies of the same gene must be present for black, a recessive gene, to show.

4. The presence of additional genes can change these two basic colors. Such as eye dilution genes which are recessives.

rr = ruby eye or R.E.D. (rr)
pp = Pink eye or P.E.D. (pp)

Agouti with R.E.D. (A/- rr) becomes fawn
Agouti with P.E.D. (A/ pp) becomes amber
Black with R.E.D. ( aa rr) becomes a beige rat
Black with P.E.D. (aa pp) becomes champagne

5. Color genes can also alter the color of an Agouti or Black rat, these are shown as:

bb - Chocolate
mm- Mink
dd - Russian blue
gg - American blue or slate
cc - Albino

All these color genes work in pairs and can be combined with others to produce different colors.

6. Figuring it all out – Punnett Squares

IF we breed a:
Beige rat that carries blue- aa rr Gg
to a blue rat aa RR gg we can figure, by using Punnett Squares, that we’ll get about 1/2 black babies and about 1/2 blue babies. All of these kittens will carry R.E.D. (ruby eyes)

Draw a grid for all known genes. Assign a box for each letter designation; match down the columns the results of the match-ups.

		B	E	I	G	E
		a	a	r	r	G	g
B	a	aa	aa
L	a	aa	aa
U	R			Rr	Rr
E	R			Rr	Rr
	g					Gg	gg
	g					Gg	gg
Results		Black	Black	Carry RED	Carry RED	Carry Blue	Blue

This chart shows that there are two possibilities that the babies can be:
aa Rr Gg
aa Rr gg
Meaning 50% will be black and carry ruby eye & blue and 50% will be blue that carry ruby eye.

Ears -
Dumbo and standard ears are types of rat ears. Standard ears are dominant, while dumbo is a recessive trait. These are shown by the symbol Du or du
DuDu & Dudu is standard ear
dudu is dumbo ear

Hair –
Rex (curly hair) is a dominate trait and is shown by Re
Rere is a rex
ReRe is a double rex …patches of hair on body.
rere is a standard hair rat
*note- there are several different types of rex, this is the basic type.

Wavy/Velveteen is a dominant (softer curl)
cucu

Hairless is a recessive trait. There are several genes that can cause hairless.
fz/fz – fuzzy
hr/hr – hairless

The Lingo

Recessive: A gene that is not “expressed” unless there are two copies. One comes from each parent.

Expressed: What the rat looks like, his Phenotype.

Carries: Recessive genes that the rat has that are not expressed or his Genotype. These may show up in Progeny if bred to a rat that carries or expresses the same recessive.

White Spotting Gene (aka: American Husky, High White, Aurora)
Anyone choosing to breed any rat that carries the white spotting gene should be familiar with megacolon. Megacolon is a symptom of the white spotting gene forming at a poor time during fetal development. Megacolon (MC) forms during the fetal development of the neural crest. This interference causes the nerves that serve the colon to not develop properly or incompletely. A kitten with MC will or may appear normal until weaning or starting solid foods. The symptoms develop between 3 and 6 weeks (average). Symptoms include bloating and intermittent diarrhea. There is no known treatment that stops it from happening.

On to Color Codes

Markings

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Rattie Rascals Rattery
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