Just as in humans, a
rabbits chromosomes are strings of DNA that act as building blocks or
blueprints that determines the final characteristics or traits of the
animal. Each chromosome has an individual spot or location (loci) in
which a specific gene is attached. When two chromosomes combine
together they form a chromosomal pairing in which each chromosome
supplies one gene to make a genetic pair. These gene pairings then
act together, alone or in combination with other genes and modifiers
to determine a rabbits overall coat and hair appearance. To be more
accurate, each gene is further categorized by it's specific function
or property known as alleles (which are different versions of the
same gene). So for the remainder of these three articles we will
refer to the individual gene's variations as alleles.
This is of course a
pretty basic statement, and you could examine the structure of DNA
and chromosomes until your eyes glaze over, but suffice it to say all
you need to know is that both the buck and the doe each contribute
one chromosome to their offspring. These chromosomes when paired
together each supply one part of a gene (allele) pair that
individually or in combination with other allele's determine their
offspring's appearance (body shape, ear size, coat color and patterns
etc…). Before we get into the second article in this series, you
need to understand a few terms as well as understand how the gene's
allele's when paired together work to determine your rabbits final
coat color and pattern characteristics.
First of all, every
allele is classified as either 'dominant' or 'recessive'. For
scientific notational purposes all allele's classified as dominant
are represented by a capitol letter, while their recessive
counterpart(s) are represented by a uncapitalized letters. A dominant
allele is just that, it dominates the pairing. For any pairing in
which there is at least one dominant allele, the characteristics of
that dominant allele almost always supersedes those of the recessive
allele. Most dominant allele's express themselves completely
suppressing any characteristics of the recessive allele. When this
happens it is called complete dominance. However, recessive allele's
can modify the expression of the dominant allele making subtle
changes to the overall genetic outcome. When this happens to
relationship of the dominant allele in regards to the recessive
allele is called incomplete dominance. In addition, an allele pair
can be made up of two recessive allele's which may produce a totally
different outcome.
So what exactly does
all this dominant and recessive gene mumbo jumbo mean? To keep it
simple, a rabbits dominant allele traits are visually apparent over a
recessive allele. That means you can see them when you look at the
rabbit. A rabbit's recessive allele traits are not visually apparent.
That means the characteristics of the allele are there, but you
cannot visually see them.
As a quick example
of how gene dominance works we are going to examine the B-series gene
whose allele pairings are responsible for producing black, blue (we
will discuss blue coloring in our second article), and brown hair
colors in rabbits. When it comes to color, almost all rabbits will
carry either the black or brown allele.
There are only two
B-series gene allele's black or brown. The combination of these two
allele's determine whether the rabbits base coat color is going to be
black or brown. Since black is the dominant allele in this pair it is
represented by the capitol letter 'B', because brown is the recessive
allele in this pair it is represented by the uncapitolized letter
'b'. As the B-series gene is made up of a combination of these two
dominant and or recessive alleles, when writing them we indicate the
dominant black allele as (B_), and the recessive brown allele as
(b_). We use the '_' to denote the second allele which is absent in a
paring when we do not know what it is yet.
As mentioned
earlier, the buck and the doe each supply one chromosome to their
offspring to complete the chromosome's genetic pairing. As the
B-series gene has only two allele's black (B_) and brown (b_) there
are only three possible allele combinations. Their offspring can have
two dominant black allele's (BB), one dominant black allele and one
recessive brown allele (Bb), or two recessive brown allele's (bb).
Because black (B_) has complete dominance over brown (b_), any
combination of these allele's in which there is at least one black
allele (BB, or Bb) will result in black offspring. When two recessive
brown (b_) alleles complete the pair (bb) then the offspring will be
brown.
Terms Or Definitions
Alleles: Are
different versions of the same gene that can occupy the same position
on a particular chromosome and control the same characteristic such
as hair or eye color. Rabbits are diploid organisms because they have
two alleles, one at each genetic locus, with one allele inherited
from each parent. In
our previous example, we examined the B-series
gene that could made up of pairs of either black (B_) alleles, brown
(bb) alleles or a combination of the two.
Chromosome: A string
of DNA made up of individual points (or loci) called genes. Rabbits
cells contain two sets of chromosomes, one set inherited from the
mother (doe) and one from the father (buck). These chromosomes
combine together to make pairs in which they share genes.
Genes: Are the
working subunits of DNA. They hold the blueprints or genetic
instructions that determine the rabbits genetic makeup (body size,
composition, hair color etc.) Genes come in multiple variations called
allele's which make up the gene pairing.
Conclusion
This is just a quick
example to show you how a chromosome's genes (and all it's allele
variants) work together to determine one color aspect of your rabbits
potential coat color. Now that you understand the 'lingo' it's time
to look at are second article 'New Zealand Rabbit Genetics Part 2:
Hair Color: It's In The Genes' for in in depth look at how to determine the color
characteristics of your breeding rabbit's and what to expect when you
breed specific color combinations of New Zealand Rabbits. I know
there may be a lot of new terms that many people are not familiar
with when it come to genetics and I will try and keep this
information as simple as I can. Maybe the following line drawing will
make my ramblings more clear. As always, if you have found this
article interesting or informational please share it with your
friends. Don't forget to follow us on Facebook or on Google+ for the
latest articles on our blog related to raising your own meat rabbits.
In a nutshell:
Two individual
chromosomes, each come from each parent.
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These chromosomes combine to make one chromosomal pair in the offspring's cells.
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This chromosome pair Is made up of multiple genes (A, B, C, D, etc…)
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These genes are made up of individual genetic variations called allele's.
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The allele's of the B-series gene that we examined in this article were black (B_) and brown (b_).
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Related Articles:
New Zealand Rabbit Genetics Part 2: Coat Color: It's In The Genes.
New Zealand Rabbit Genetics Part 3: Putting It All Together.
Additional References:
New Zealand Rabbit Genetics Part 2: Coat Color: It's In The Genes.
New Zealand Rabbit Genetics Part 3: Putting It All Together.
Additional References:
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