Any Color or Combination
Elektrik Borzoi ™
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Any Color or Combination |
Elektrik Borzoi ™
Do You Feel Lucky?Genetics for Breeders, Part 1 |
My father on occasion has reminded me that it is better to be lucky than smart. Unfortunately I have never been the lucky sort, so I have found myself slaving over subjects in hopes of understanding something useful.
How do you know if you are lucky? Do you win the jackpot every time you play the lottery? If so, read no further -- you don't need any help. Actually give me a call, and share your numbers with me.
Genetics and breeding are a lot like gambling. All share random events and seemingly bewildering odds to the average person. We often hear metaphors like "breeding is a crap shoot" or "roll the genetic dice." The implication is that somehow the odds are stacked against us. Our only hope of success being some positive intervention by the hand of fate. The application of genetics to breeding is even more confusing given our current level of knowledge. While more is known about the principals of genetics, our specific knowledge of dog genes is pitiful. It is unknown if this state of affairs will improve markedly in our lifetime.
Despite of these limitations, we still can draw numerous conclusions using just the genetic principals that will positively influence our breeding programs.
In this situation, why worry about genetics? Simply it can improve the odds of your success. The secret to using genetics lies in its similarity to card games. Much like counting cards improves the odds of winning at various card games such as Blackjack ( or 21 ) and even Bridge. Genetics is not magic. It will not guarantee you can breed Best in Show or even champion borzoi. It will help you make better decisions regarding your breeding program. Genetics should not be the only tool in your breeding program. It is possible to build a house using only a hammer, but you will build a better house if you also use a saw, cement mixer and other tools. You will achieve more success if you also use other breeder tools. There are various selection models to help evaluate your breeding stock's quality. The type of breeding program used will also influence your success.
The basic principals of genetic theory are remarkably simple. You don't really need to know terms like alleles, heterozygous, or homozygous to began applying genetics to your breeding program. You may eventually want to understand these terms and other finer points of genetics. However, they are not needed to the apply genetics to your breeding programs. The genetic principals we will begin discussing are:
For each trait in an animal:
I am partial to illustrating genetic principals with a deck of cards. The particular advantages to this metaphor will become apparent as we proceed. In the "genetics card game", the rules are simple. However the genetic deck of cards is about 2,000 times the size of a regular deck of cards. Let us examine these rules along with their genetic and breeding analogies.
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Genetics Card Game |
Genetics / Breeding Analogy |
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You start with two decks of cards.
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A male and female breeding pair. |
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Each deck is divided into 2 equal piles with only one pile from each deck is used. How we divide each deck into its piles will be discussed later.
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Half of each parent's genetic code is available to each offspring. |
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Two cards are dealt for each trait - one from each of the chosen piles. For example, a 10 and a 6.
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Both parents will contribute to an offspring's trait. |
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The high card for each trait is always face up. The other card is face down. Aces are low and kings are high. Using the cards we just dealt, we would see:
Although in this case, we know the face down card is a 6, without further evidence we would normally only know the card is a 10 or less. |
Only half of an offspring's genetic code can be seen directly. |
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A card's face value has nothing to do with whether it is a desirable or undesirable trait. The face value is merely used to determine which card is turned face up. |
The dominance or recessiveness of a trait does not determine its desirability. The Standard and the breeder's preferences determine desirability. Consequently, some traits will be easier to make visible than others will. |
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The order of all cards in decks or piles is preserved. In our example we know one parent had a 10 and the other had a 6 in the genetic code that defines that particular trait. Without further evidence we do not know whether these traits were visible or not in either parent. |
The genetic code inherited for a particular trait can be traced to one half of each parent's code for that trait. |
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Regardless of the number of rounds (traits) you choose to play ( or evaluate ) - all cards in each pile will be dealt into pairs. Even if you are unaware more cards exist.
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The number of genetic traits is a very large fixed number for each animal. |
Having lulled you, with the apparent simplicity of genetics -- the more common pitfalls in applying genetics will be addressed.
The traits we evaluate only reflect a tiny portion of the actual genetic composition of an animal. No matter how many factors we evaluate in selecting a breeding pair we are overwhelmed by the full gamut of genetic choices. Mother Nature has given us dogs with traits numbering in the 100,000 range. So if you are evaluating 100 different factors, this represents only 0.1% of all the traits being determined by the breeding. Should we be concerned with what appears to be a 0.1% solution? The consequences of either overlooking large numbers of traits or over aggregating them may lead to results where our analysis will be dubious. Whether we choose to evaluate a trait or not in selecting our breeding pairs--Mother Nature make sure each and every genetic choice is filled.
There is no magic solution to even such odds. All we can be expected to do, is to be as thorough as possible. Using 10 or 20 factors is almost assuredly inadequate to produce better results. Using 100 or 200 may be sufficient to start seeing more successes from your breeding efforts. How can so few traits yield such dramatic results in the face of apparently overwhelming raw numbers? The traits we choose to evaluate most likely are controlled by large groups of the actual genetic code. For example coat colors are attributed to 10 to 20 different potential genetic markers. Extending this knowledge to our dilemma, we realize the traits that we evaluate comprise some multiple of the actual genetic code. It is this multiple that amplifies our success rate. Such a multiplier's impact on 100 traits would influence 1,000 to 2,000 or more pieces of the genetic code. Regardless of what the actual multiplier is, it is incumbent upon us to ensure our selection process crosses some threshold of completeness and include a sufficient number of factors before we will realized better breeding results.
Everyone knows each parent is 50% responsible for each of the offspring. What we often forget is genetics is the model of fairness. The offspring don't get half their traits from each parent -- they get half of each trait from each parent. Each and every genetic trait of the offspring recieves half of its code from each parent. What we see in the offspring is determined by the relative dominance of each parent's contribution. Determining which half of a trait an offspring receives is decided by what amounts to a coin toss. Heads for the visible portion and tails for the mystery portion. To further confound us, the chosen pieces are reflected by dominance not the blending of values. If an offspring wins both mystery portions of a trait--what should we expect? How these pieces exhibit themselves in an offspring continues to confound the breeder.
Let us look at one trait where the breeding pair are closely matched in quality ( a Jack and a 10 ).
Offspring that look like Jacks or 10s are no surprise. The Jack and 10 cards are attributable to specific parents. We easily explain 75% of the offspring. But we will initially be perplexed both by the source and future breeding impact of the remaining 25%. Where did the 6 come from? It could have come from either parent, as both the Jack and the 10 dominate the 6. Of further note, we are unable to distinguish the offspring that look like Jack that have a hidden trait of 10 from those whose hidden trait is still a mystery. The one important question we will postpone is how important are the differences quality between a Jack and a 10.
Examining a breeding pair where a trait is less closely matched ( a 6 and a Jack . ) We may see offspring giving the appearance of a blended ( averaged ) quality.
Remembering genetics has no provision for blending; we must look for an alternate explanation. Since an 8 is greater than a 6, the 8 must have been the hidden genetic code of the parent a more dominant trait, the Jack. The more dominant trait is not necessarily the more desirable trait. In this example, 50% of the offspring exhibit the trait somewhere between the qualities of their parents. It may also be prudent to consider the possibility of excessive aggregation in the trait we are evaluating. Overly broad traits will also produce a similar outcome with no clues to genetic composition of the parents. ( A topic for a later article.)
If offspring from the preceding pair was more diverse, it provides a different type of conclusion.
The appearance of offspring with traits less dominate ( more recessive ) to that of either parent suggests that for at least one parent - this trait is the most dominant of hidden genetic code. We know in this example that the 3 could have been hidden in either parent. But the real bonus is the knowledge that the question mark card is a 3 or less. The hidden code in this offspring potentially harbors an even more recessive form of the genetic code.
By now you must realize much of the initial genetic information we gather is a forensic effort.
The alternatives are
Do you feel lucky?
Buy a lottery ticket instead and see what happens.
End
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