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Understanding
genetics is great, but so is finding raisins for us! |
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INTRODUCTION
| DEFINITIONS | THE COLOR
GENES | MY NOMENCLATURE
Well, here it is - the last page for me to write for my site and the one that I've sweated over more than any other. It is also one that I've quite enjoyed doing! Much of this information was derived from a combination of several other genetics pages on ChinNet which you may want to visit. Much thanks goes to Dea Freiheit of Pacific Northwest Chinchillas for all of her time and patience in helping me work all this out in my head. A much more thorough study of the subject can be found in Alice Kline's book, "Basic Genetics and History of Mutation Chinchillas", available through MCBA (Mutation Chinchilla Breeders Association) - Julie Ouderdirk, Secretary/Treasurer, 3661 E. Baker Road, Midland, MI 48642. For
some more excellent information I would suggest a visit to the Definitions (if you want to just skip this section to go right to the possible breeding outcomes then go here ) ALLELES | CARRIER | CO-DOMINANT GENES| CO-RECESSIVE GENES | DOMINANT GENE | GENES | GENOTYPE | HETEROZYGOUS | HOMOZYGOUS | INCOMPLETE DOMINANT GENE | LETHAL FACTOR | PHENOTYPE | POLYGENIC | RECESSIVE GENE | WEAKLY DOMINANT ACCUMULATIVE GENE ALLELES - An allele is a pair of genes for the same trait. In this case I will only be discussing alleles for color traits, but there is much more to consider when breeding chinchillas - size, coat quality, conformation, temperament, congenital disease, etc. CARRIER - An animal is referred to as a "carrier" of one or more recessive color genes if it carries a heterozygous or polygenic allele with one or more dominant genes and one or more recessive genes. For instance a TOV/White Mosaic/Violet carrier has a gene structure of dominant TOV + dominant White + recessive Violet. The violet color won't show phenotypically, but the animal is a Violet carrier and may throw that gene when bred. CO-DOMINANT GENES - When two or more dominant genes exist polygenically. Some examples are: Velvet + Beige =
Brown Velvet (TOV Beige) CO-RECESSIVE GENES - When two or more recessive genes exist polygenically, like Violet + Sapphire = Violet Sapphire DOMINANT GENE- A gene whose trait will develop in the offspring even though it is present in the genetic material of only one of the parents, hence heterozygous in the offspring. The dominant genes for color are Velvet (TOV, Touch or Velvet, or Black), Beige, and White. Standard is recessive to them. Standard is then dominant to Charcoal, Violet, Sapphire, and Recessive Beige which are all recessive to everything. White is actually an incomplete dominant gene, hence the ability of the underlying Standard gene to show through in different degrees - Wilson White, White Mosaic, or Silver. Ebony is a weakly dominant accumulative gene and is therefore expressed to varying degrees (depending upon how many generations of Ebony are bred in) with either dominant or recessive colors. GENES - The basic unit of heredity. Heredity traits are controlled by pairs of genes in the same position on a pair of chromosomes. These gene pairs, or alleles, may both be dominant, both be recessive, or may be polygenic. GENOTYPE - The basic hereditary combination of genes in an organism. This is not to be misconstrued as "the parents necessary to produce a certain color", as several different combinations could possibly produce the desired color of offspring. HETEROZYGOUS - Heterozygous alleles are gene pairs consisting of two or more different genes. HOMOZYGOUS - Homozygous alleles are gene pairs consisting of two of the same gene. Some genes cannot exist in the homozygous state due to a lethal factor (i.e.. White and Velvet). INCOMPLETE DOMINANT GENE - A dominant gene whose trait is expressed in varying degrees with other genes. White is an incomplete dominant gene for color in chinchillas and, in combination with Standard Grey, results in either White Mosaic, Wilson White, or Silver. When combined with homozygous recessive colors (i.e.. White + Violet, White + Sapphire), the recessive color trait will appear in varying degrees. Beige also seems to have an incomplete nature as homozygous recessive colors will be visible with it. WEAKLY DOMINANT ACCUMULATIVE GENE - A gene whose trait is expressed polygenically even in the heterozygous state with either dominant or recessive genes in varying degrees, depending upon how many generations of this gene are bred into an animal. Ebony is an example of this. LETHAL FACTOR - This term refers to the inability of certain genes to exist in the homozygous state. The two lethal genes for color involved in chinchillas are White and Velvet (also referred to as TOV - "Touch of Velvet" - or Black, not to be confused with Violet). If a homozygous allele of White + White or Velvet + Velvet results from a breeding, the embryo will never develop but be reabsorbed by the mother. It has been said that this may result in a blocked uterine horn (chinchillas have two horns to their uterus that branch out from the cervix). PHENOTYPE - The physical appearance or makeup of an individual. A group of individuals who resemble each other phenotypically may differ in genetic makeup. Conversely, a group of individuals who are identical for color genotypically may differ phenotypically. This is often the case when the weakly dominant ebony gene is present. POLYGENIC - Pertaining to or caused by several genes. Traits that are determined by a series of gene pairs are referred to as polygenic. Some common examples of polygenic colors involving co-dominant genes in chinchillas are Pink White (Beige + White), Black Velvet (TOV + Standard), and Brown Velvet (TOV + Beige). An example of a polygenic color involving co-recessive genes are Violet Sapphire (Homo Violet + Homo Sapphire). It gets much more complicated with, for instance, a TOV/Ebony/White Mosaic/Violet carrier or perhaps TOV/Tan/Sapphire carrier where dominant, weakly dominant and recessive genes are involved. The possibilities are almost endless and polygenic traits are very difficult to predict as there are many possible gene combinations when breeding these animals. RECESSIVE
GENE - A gene whose trait will not be expressed in the heterozygous
state but will only be expressed in the homozygous
state. The recessive genes for color in chinchillas are Violet,
Sapphire, Recessive
Beige, and Charcoal (sorry - not dealt with here until I learn more).
The
Color Genes BEIGE
- A dominant gene. A chinchilla referred to as
just Beige CHARCOAL - A recessive gene. A chinchilla referred to as Charcoal is genetically Charcoal + Charcoal. This chinchilla looks like a medium light Hetero Ebony. It can be hard to differentiate them if the animals pedigree is uncertain. EBONY
- A weakly dominant accumulative gene. There
is a lot of confusion and disagreement about whether Ebony is incomplete
recessive or weakly dominant, but I'm going with the information in the
recently released "Basic Genetics and History of Mutation Chinchillas"
book put out by MCBA. A chinchilla referred to as just Ebony RECESSIVE BEIGE - A recessive gene. A chinchilla referred to as Recessive Beige is genetically Rec. Beige + Rec. Beige. They look very much like the dominant beige except that the eyes are either a very clear red like jelly beans or black like a Standard or White. I won't be including this color in my list of colors as I'm still uncertain about how it behaves genetically, although I believe it is a simple recessive gene, plus I'm considering the fact that it is such an extremely rare color mutation. SAPPHIRE - A recessive gene. A chinchilla referred to as Sapphire is genetically Sapphire + Sapphire. This chinchilla looks like a very light Standard, with a distinctly bluish cast and pink ears. STANDARD
- The original wild color, often referred to as Standard Grey or just
Grey, this gene is recessive to Beige, Velvet
(TOV, Black), and White. It is weakly dominant with Ebony. It is dominant
to Charcoal, Recessive Beige, Sapphire, and Violet. A chinchilla referred
to as simply Standard VELVET
- A dominant gene, also referred to as TOV (Touch
of Velvet)or "Black". This gene, like Ebony, is a gene for color
PATTERN rather then color. It darkens and solidifies any color that it
is combined with, creates a distinct contrast between the back and tummy
color, and causes distinct stripes on the front paws. Hence, a Black
Velvet VIOLET
- A recessive gene. A chinchilla referred to
as simply Violet WHITE
- An incomplete dominant gene. White Mosaic
My Gene Nomenclature Before working out the Punnet Squares for many of the possible color combinations I need to clarify the nomenclature that I will be using. I have changed from my previous writing to now use the MCBA recognized and accepted nomenclature for the sake of creating universality. Here are the abbreviations you will see:
*Standard is one gene whose nomenclature I'm dealing with differently then MCBA for the sake of simplification. Standard carries the possibility of all colors so is actually blbl/ww/pwpw/bb/BB/VV/SS/PP/PrPr (and some others that I'm not even dealing with). Because only that part of the formula pertinent to the mutation under consideration is used, a Heterozygous Beige in MCBA nomenclature would be Pwpw. In my nomenclature it is Pw/Std. Black Velvet would be Blbl. For me it's Bl/Std. That makes your basic Standard much easier: Std/Std! ** I am not using the Charcoals or Recessive Beiges in my charts, but they would be worked out the same as the other recessives. Please understand that "the jury is still out" as to accurate genetic formulas for each color mutation. Much research is still in progress. The "Gene Formula" describes an animal's genetic capabilities. I prefer to use the term "TOV" rather then "Black" as I believe this can be confusing for the novice who is trying to understand the difference between Black and Ebony. To learn how to use this information in Punnet Squares to figure out the possible outcomes of your breeding efforts go here To
see the possible outcomes when breeding some of these colors you
can click on those colors that are underlined. I'm getting started on
this, as of November '01.
Standard/Dominant colors
Dominant/Dominant Hybrids
Recessive/Recessive Hybrids
Dominant/Recessive Hybrids
Several people have inquired about a more easily printed copy of these charts. For these you can just go here. Punnet Squares To determine the possible outcomes of breeding we use a Punnet Square. The genes of one parent are listed across the top and the genes of the other parent are listed down the side. The resulting alleles then appear in the table. To determine the genetic formula of the offspring go back to the tables above. Here are some examples to help you get started on making your own:
Beige x Beige
Beige x Black Velvet
White x Brown Velvet
Homo Pink White
+ Beige/Violet carrier
It
is my hope that with the gene formula that I've provided, you'll be able
to work out your own Punnet Squares to figure out the possible outcomes
of your breeding efforts. My
next step in completing this study is to go ahead and work out many of
the squares for you and figure out all of the possible
outcomes. As of November '01 I've gotten started on this project. You
can click on the underlined colors in the above chart to see that squares
that I've done so far. There are over 2000 possible pairings here, so this project could take quite a while!! For now, if you have a specific pairing that you need help figuring out just send me an email and I'll try to get back to you (sometimes difficult to do - sorry). |
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Last
updated June 2002 |
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Click on me to send an email to Amy- sometimes it's very hard for her to get back to you - sorry! |
click here to see some great Christian websites |
| © | 2002 - AMY HAMOVITZ - CHINBIN IN OREGON | VISITOR
NUMBER  SINCE
MAY 2002 |
For
those of you who have been here before, I have made some major changes
and more updates are coming. I hope this makes the study of chinchilla
genetics somewhat more clear. - Amy
