Quote:
Originally Posted by ILOVECORNSNAKES
thanks to all who answered! i still dont understand how it works but now i know what it means when im reading it
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This might get confusing, but I will try:
Take, for example, a Motley Snow corn. A snow is a combination of anerythrism(no orange or red pigments) and amelanism(no black pigment), motley is a pattern mutation. There are three genes at work here...amelanism, anerythrism, and motley. Since this snake is visually identifiable as all three recessive traits, it MUST be "homozygous" for all three traits. To give you a visual, writing out the allelic combinations would look like this, using "a" to represent amelanism, "b" to represent anerythrism, and "m" to represent motley:
aabbmm
A snake that is "heterozygous" for snow motley would look like this:
AaBbMm
Notice in the first example, the snow motley, that all the letters are lowercase. This represents a matched pair of recessive genes at each locus(position). This gives you the recessive "phenotype" or look. In the second example, one gene is represented by a capital letter, which is the wild type gene at this locus, and one is lowercase...the recessive. The second snake would not LOOK any different than a normal corn snake, but is still carrying the recessive genes. This is known as "heterozygous".
If I were to breed snake number 1 with snake number 2, it could be represented like this:
aabbmm X AaBbMm
This breeding would produce many different combinations. Using
FOIL(first, outer, inner, last) to pair up all possible combinations at each locus, I get these possibilities:
Amel locus:
Aa or aa
Anery locus:
Bb or bb
Motley locus:
Mm or mm
These are the only possible combinations at each locus, however, they can be combined in MANY different ways. This pairing will produce offspring that are:
normal het. amel het. motley het. anery(AaBbMm)
motley het. amel het. anery(AaBbmm)
amel het. motley het. anery(aaBbMm)
anery het. motley het. amel(AabbMm)
amel motley het. anery(aaBbmm)
anery motley het. amel(Aabbmm)
snow het. motley(aabbMm)
motley snow(aabbmm)
Since snake number 1 is "homozygous" and SHOWS all three recessive genes, it MUST possess the recessive gene on BOTH alleles at each locus. This means that snake number 1 can ONLY give the recessive allele to every offspring. Snake number 2 is "heterozygous" at each locus, and therefor can give the wild type OR the recessive allele to every offspring.
I hope that makes some sense to you. If you read the three books I mentioned in my earlier post, you will find yourself "talking shop" about corn snake genetics in no time...