One of the most distinctive characteristics of living organisms is the ability to reproduce. It is just this characteristic that is the foundation of our hobby, namely the breeding of birds.
Mutations are the basis of the adaptive improvement of the genetic composition of all living creatures.
The mutations, which originated in the canary community, would not stand a change to survive in the
natural state. The wild type is and will stay the most successful there.
There is an important phenomenon which often is seen as a "mistake" of mother nature and that is
recombination better known as crossing-over. All living organisms posses recombination systems
which are targeted on bringing together independent mutations originated in different individuals.
The reason for that is that certain mutations in combination with each other might be favorable for an
individual. In our case the aim is not to join certain properties as well as to combine specific colour
shades in one bird. If it is known that specific factors are linked on one chromosome, or just not, thus
divided on two homologe chromosomes, than you may experience some unexpected results during the
breeding season. The recombination after which suddenly two sex-linked mutations arrive together on
one chromosome, occurs simply by the random assortment of these chromosomes into daughter cells
at the first meiotic division. However, if genes are on the same chromosome, recombination requires
crossing-over of non-sister chromatids from homologous chromosomes. This occurs during the first
meiotic division, when homologous chromosomes are paired.
The primary function of meiosis is the regulation of the recombination and therefore crossing-over may
not be considered a "mistake" because the whole system is part of the mechanism of survival of the
individual while as a secondary function crossing-over also provides a means of repairing damage to
the genome. Crossing-over results in an exchange of genetic material between the maternal and
paternal chromosomes. Double crossing-over does occur also and make that part of the crossovers
stay undiscovered.
In long chromosomes, like the Z-chromosomes, the occurrence of more than one crossing-over never
leads to a crossing-over value (COV) higher than 50, in other words, if we determine the COV of
specific factors, the crossover frequency will never exceed 50%.
The percentage found shows us the relative distance between two loci (factors) and in case more than
two loci are involved also their position with respect to each other on the chromosome.
The crossing-over phenomenon was first discovered and described by T.H. Morgan [5]. The relative
distance between two loci is therefore expressed as centiMorgan.
When I started studying colour inheritance in canaries a few years ago, it attracted my attention that
there were some matters that might be very interesting to do some research on. One of these matters
was the fact that there is a colour shade in existence known as "isabel", however, it is in fact a
combination of cinnamon and agate, actually a cinnamon-agate.
Yet, and I have published this already a few years ago, people sometimes write about it if it is a
separate mutation, but after studying this it appears to be a mutation-combination.
The first effort to map the avian sex-chromosome was done in fowls [4,6,15] and later on in
Budgerigars [9,14].
Soon it became clear that sex-linked cinnamon and ino in Budgerigars map very close together, about
3 centiMorgan representing a COV of 3% (= 1:33). After some time this value was confirmed for
several other psittacine species and cinnamon-inos as well as cinnamon-pallids have been found in
almost all species investigated thanks to large-scaled breeding programs.
It was already obvious to me that there was a major difference in composition of the sex-chromosomes between psittaciformes-
and finch-like birds because many finch-like species have produced
a sex-linked pigment diluting mutation called "pastel". Such sex-linked pastel mutation is lacking
completely in psittacine species which is very remarkable.
The question arose if it would be possible to investigate the relative distance between equivalent
sex-linked loci in psittacine- and finch-like birds. Cinnamon and agate (the latter is homologue to pallid
in psittacine species), proved to be excellent candidates for this research project, agate is an allele of
satinette (ino) in canaries just the same as pallid is an allele of ino in psittacine birds and both
mutations are very popular in the canary community.
In order to obtain some answers to this question the working group named "Development and
Innovation in Canaries" in which I participate, made an appeal to obtain breeding records from
breeders who cross-breed cinnamon and agate canaries. Two independent breeders responded so far
and I find their results spectacular to such a degree that I decided to publish
them.
The first breeder used 6 different cocks born in 2000 and offspring of a normal green cock mated to a
cinnamon-agate (isabel) hen. All male offspring out of this mating are split cinnamon and agate linked
on one Z-chromosome.
These cocks were mated to satinette-, green- and Hartz roller hens. Normally one would expect two
genetically different types of hens namely normal hens and cinnamon-agate (isabel) hens. In reality 20
hens hatched from which 6 agates, 6 cinnamons and 8 cinnamon-agates. The agates and the
cinnamons are the result of crossing-overs, the cinnamon-agates were expected. That makes 12
crossing-over hens out of a total of 20 which is remarkable.
A disadvantage of this type of mating is that we cannot detect possible crossing-over cocks in the
offspring. We will have to wait until the next generation to see what kind of daughters these cocks will
produce. However, we will never obtain reliable results because these cocks will probably also
produce a high percentage crossing-overs in their offspring.
Most interesting breeding results were send to me by a German breeder. He collected breeding results
from 1990 till 2002 and used cinnamon, agate, cinnamon-agate and cinnamon-satinette hens. With
such matings we are actually able to detect crossing-over cocks in the offspring making the calculation
of the COV much more accurate than in the previous mentioned matings.
The cocks he used were normal/cinnamon/agate, normal/cinnamon-agate, agate/cinnamon and
cinnamon/agate. The most interesting matings are shown in the next table.
mating | expected cocks | expected hens | c.o. cocks | c.o. hens |
Cock normal/cinn/agate X Hen cinnamon-agate |
25% cinnamon/agate 2 specimens 25% agate/cinnamon 3 specimens |
25% cinnamon 4 specimens 25% agate none |
normal/cinnamon-agate 3 specimens cinnamon-agate 3 specimens |
normal 4 specimens cinnamon-agate 2 specimens |
Total amount youngsters 21 of which 6 c.o. cocks and 6 c.o. hens, a total of 12 : 21 |
mating | expected cocks | expected hens | c.o. cocks | c.o. hens |
Cock normal/cinn-agate X Hen cinnamon-agate |
25% normal/cinn-agate 1 specimen 25% cinn-agate 3 specimens |
25% normal 1 specimen 25% cinnamon-agate 1 specimen |
agate/cinnamon 1 specimen |
cinnamon 2 specimens agate 1 specimen |
Total amount youngsters 10 of which 1 c.o. cock and 3 c.o. hens, a total of 4 : 10 |
mating | expected cocks | expected hens | c.o. cocks | c.o. hens |
Cock normal/cinn/agate X Hen agate |
25% normal/cinn/agate 1 specimen 25% agate none |
25% cinnamon none 25% agate none |
none | cinnamon-agate 2 specimens |
Total amount youngsters 3 of which none c.o. cocks and 2 c.o. hens, a total of 2 : 3 |
mating | expected cocks | expected hens | c.o. cocks | c.o. hens |
Cock normal/cinn/agate X Hen cinnamon-satinette |
25% cinnamon/satinette 1 specimen 25% normal/agate/cinn-satinet none |
25% cinnamon none 25% agate none |
none |
cinnamon-agate 4 specimens normal 1 specimen |
Total amount youngsters 6 of which none c.o. cocks and 5 c.o. hens, a total of 5 : 6 |
If we take a good look at the tables the high amount of crossing-overs attracts attention. The total
amount of investigated matings was higher than shown in the tables but just to show what happens I
have displayed the most spectacular matings in these tables.
In order to determine the crossover value (COV) for cinnamon and agate, I counted the total amount
of offspring over a period of 11 years and found a total of 52 birds. The total amount of crossing-overs,
those from the table shown including some crossing-overs found in matings not shown in the
table, came to 24. That means that the provisionally COV between cinnamon and agate is 24/52 = 46.1%.
If we compare this with the COV of the equivalent sex-linked loci in psittacine birds (COV between
cin and ino or ino pd = 3%), than we have to deal with a significant difference. So the relative distance
between these consonant factors in finch like species compared to psittaciformes differs
considerable despite of the fact that they might have had a possible common ancestor. The difference
is displayed in table 5.
When more results become available, the percentage will become even more accurate but I don't
expect this to be a significant difference compared to what I have found so far.
Because agate and satinette both are alleles of the sex-linked ino-locus in canaries, the COV of cinnamon and
satinette is equal to cinnamon and agate. That means that the chance to breed cinnamon-satinettes is
equal to the chance of breeding cinnamon-agates. Testmatings between sex-linked pastel ( pa) and
agate (inoag ) will show the relative distance between these two loci in order to map
other uncharted areas of the sex-chromosome of the canary.
I am very much indepted to the following persons:
mr. H. Barnas from the Netherlands and mr. N. Schramm from Germany who kindly put
their breeding records at my disposal.
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