Mutation

  • The crossing-over

    It was in 1960 that the first zebrafinch pale Brown back appeared in Belgium.
    Let us try to understand how such a combination of colours could have been born.

    It is known that the brown and pale back factors, related to sex, are located on X chromosomes, but different and at different locations (loci): (1) and (2).
    They are therefore not normally linked (otherwise all the browns would also be pale backs: which is not the case).
    How could they get linked on the same chromosome ? (3)

    Crossing over1 1

    When you mate a brown male with a pale gray back female (or vice versa), each time you get gray males, carriers of brown and pale backs. Each male therefore has two different X chromosomes: One carries the "brown" "no light back" genes, the other carries the "no brown" and "light back" genes. Being recessive, none of these genes can be expressed since they are in a single copy; being non-alleles, neither can dominate the other; It is therefore a natural gray color that is expressed.

    How will these genes be transmitted by the male to his offspring ? To understand it, some explanations are necessary.

    Chromosomes are very long molecules (2 millionths of a mm thick, average 5 cm long in humans) that are normally entangled with each other in the nucleus of the cell. At the time of meiosis (cell division allowing, in males, the formation of spermatozoa from the mother cells of the testes), these chromosomes split into two rigorously identical chromatids linked together by a centromere.
    Each chromatid then spirals. Only then does the chromosome become visible under the optical microscope. The chromosomes group together and join two to two homologous pairs.

    During this phase, two chromatids of the two joined chromosomes can cross, break and then join together by exchanging more or less important segments. This is the phenomenon called spanning.
    The “brown” gene could thus be found linked to the “pale back” gene on the same X chromosome. A gray male with brown back and pale back can (but only this way) produce pale gray, gray, brown back and pale brown back females. (12.5% of each).

    With this crossing over, this same male could also have:

    • Crossed with a pale back female: 12.5% of pale gray back males split brown.
    • Crossed with a brown female: 12.5% of brown males split pale backs.

    By mating one or the other of these with their "pale brown back" sister, it is possible to obtain (in 3rd generation): 25% pale brown back males and 25% pale brown back females.

    L enjambement image 2

    CHROMATIDE

    A : Normal
    B : Spirally contracted
    C : Schematized

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  • Zebrafinch genetics : Instructions

    1. Introduction

    The breeding and competition of zebrafinch has grown considerably over the past fifteen years. In order to improve the size of the new mutations, breeders also have recourse to conventional "split" birds.
    Some manage to combine several mutations. All this made it essential to know a minimum of applied genetics. It is this minimum that I would like to present to novice breeders.
    This is not a complete course in genetics, but a simple presentation of the method I use preceded by some basics.

    2. The zebrafinch and its mutations

    A zebrafinch has a number of visible characters (size, shape, designs, color, sex) that constitute its phenotype. It can have, in addition to other unexpressed traits (it is said to be a split). The set of traits, expressed or not, is called the genotype.

    A young zebrafinch grows out of an egg cell, the result of the fusion of the nucleus of a father's sperm and the nucleus of the female's egg. The bird's genetic program is already there: A series of cell divisions and coded information will (or not) trigger the appearance of the characters. The encoded information is carried by genes located on long filaments contained in the nucleus: chromosomes.
    All chromosomes go in pairs: each chromosome therefore has its counterpart.

    There are two categories of chromosomes :

    - Sex chromosomes :
    • XX in the male
    • XY in the female

    - Autosome chromosomes.

    The gray zebrafinch living in Australia is the source of all of our farmed zebra finches. It has a whole set of genes distributed in its chromosomes.Whenever a new mutation has appeared, there has been a change in an original gene (and it has been shown to be hereditary). The original gene and the mutated gene are located in the same place called a locus on each of the homologous chromosomes.
    Both genes are alleles.

    Genetics of zebrafinch 4

    A bird is pure (homozygous) when all of its alleles carry identical information.
    A bird is heterozygous when at least one pair of alleles carries different information about the same trait.

    We currently know about twenty different mutations of the gray zebrafinch.

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  • Gray black chest orange chest

    The objective of this article is not to impose a management of breeding or create a controversy, but to share my experience of breeding, my observations as well as the difficulties I have encountered for about fifteen years of breeding zebrafinch in this combination of mutations.

    The black breast is a mutation of design due to a different distribution of eumelanim in the plumage of the bird. The orange breast mutation is a color mutation: The eumelanin of the designs is transformed into brown orange phaeomelanin, which pulls towards the red-rust color for the best subjects. I do not think it is important to specify in detail how each mutation we already know alters on the mutated bird.

    The ideal competition male, in addition to a correct shape and size such as a classic, must have no black discharge into the chest, must have a parotic zone (the color: between the beak and the cheek) white, a chest that rises as high as possible under the beak, a strong extension of the cheeks (the cheeks meet at the back of the skull) without running on the back (which for me represents a non-selective extension of the color), a gray back and not loaded with brown veil as is often the case, drawings on primary and secondary remiges (white+orange), the most intense red/rust color possible, the largest belly design (orange flames). To this it is necessary to add that the drawings of blanks must be marked with white ovals on orange background; The drawings of the tiles of tails are of course elongated.

    The female as the male must be gray of back, shape and size correct, have a belly drawing (the flames)( note that this drawing is not orange as on the males but rather pulls towards the gray-brown), back drawings (on the outer edge of the remiges), a chest that rises very high, drawings of orange cheeks, flanks marked with dots and orange color also.

    Should the female have the darkest possible cheeks and flanks ? I have no answer.
    What is certain is that the first female orange breast had no orange cheeks and that the Dutch standard required females without cheeks a few years ago (now there are two standards accepted and judged differently: with drawing and without drawing…: type 1, type 2 in competitions). The female without drawn cheeks keeps the tail tiles as orange as possible. Most of my breeding females do not have cheeks, it is a character that I do not select specially.
    I sometimes read on the internet that to release a good intensive male in color it is absolutely necessary a female with very orange cheeks, it is not true. We come out very good colored birds with females without cheeks if they are very grey. By “very grey” I mean birds whose eumelanin supersedes phaeo. This does not mean that certain characters should not be present (belly drawing, caudal overlying, eyelid etc.). I can say that the female without cheek has no influence on the intensity of the color on the males.

    Diamant mandarin femelle gris poitrine orange poitrine noire

    Some peculiarities are specific to the mutation combination

    The orange breast seems to intensify the extension of the orange color of the drawings. We often observe subjects with a complete extension of the cheeks at the back of the skull, and this with a chest that goes up very high under the beak (compared with a pure black chest). This extension, when important, tends to color the color. I do not agree with those who say that orange-colored birds are black-faced birds. This coloration appears as well on black breast orange breast without the black face mutation for several generations.

    I do not select the orange color of the color. Certainly it is a defect present in my birds but raising black face black breast orange breast, I do not pay attention to it.
    In competitions, it depends a lot on the judges but in general, if the bird is good, they do not get heavily punished. Note that there are several kinds of orange colors, which a photo does not show well. Rusty orange colors like the chest and that come to blend with the cheek (not good) or an orange veil, lighter than the cheek and that stands out again (it goes better). But on big competitions, this is what the beautiful bird will miss to rank against the best.

    Diamant mandarin male gris poitrine noire poitrine orange1

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  • How to recognize a male split of black chest mutation

    The aim of this article is not to establish an unstoppable rule for the recognition of a gray male split (carrying) the black breast mutation. Rather, it aims to gather the clues that will allow you to identify it.
    For this, every detail of the mutation is taken over, according to what I observed during the selection of my strain of gray black chest.

    Before starting to analyze each possible clue, it seems important to me to bear in mind that the black chest mutation changes the shape of the drawings. To identify a split of the black chest mutation, I also advise you to take into account all the clues described in this article.

    Let’s proceed and analyze the phenotype of a gray black breast from the head to the rectrices in comparison to a gray split the black breast mutation. To identify each descriptive term used, you can use this diagram : Descriptive terms in zebrafinch.

    1. Mustachial line

    Black chest : The moustachial line will be pronounced and intense black.
    Split (/) Black chest : The moustachial line may be more pronounced than on a gray, however this does not constitute for me a sufficient clue.

    2. Tear line

    Black chest : The tear line disappears (ideally according to the standard) or only a fine line remains.

    Tear line

    Split (/) black chest : Different cases depending on the force of expression of the mutation in the split.

    - The tear line is present and fine :

    tear line is present and fine

    - Tear line is present and wide :

    Tear line is present and wide

    - In some cases, the tear line of a split black chest may also be absent. It will be necessary to rely on the other clues to know if it is a split or a black breast in its own right.

    3. Cheeks

    Black chest : The drawing of the cheeks will extend up and back of the head.

    extension of cheeks black chest extension of cheeks black breast neck

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  • Illustrated glossary of mutations in zebrafinch

    I made this glossary to illustrate in photos the existing mutations in the zebrafinch.
    He can help you identify the mutation (s) of your zebra finches.

    Important precision :To identify the genotype of your zebrafinch, it will be necessary to take into account that a zebra finch can carry a mutation without being mutant.
    Being a carrier (/, split) of a mutation means that it is partially present (genetically speaking). From the visual point of view the partially carried mutation will not be seen or only by some clues present in the appearance of the bird.
    In this case, it will be necessary to have a trained eye to determine the genotype. Sometimes check couplings will be necessary.
    Your zebra finch can also have several mutations, the possible combinations are numerous.

    This glossary is based solely on the phenotype (visual characteristics) and single mutations (not combined).

    Grey (GR)

    The gray zebrafinch is not a mutation, it is the original (wild) type.

    Gris male Gris femelle

    1. Gender-related mutations

    The female can never be a split, so she is either mutant or non-mutant.
    The male can be a split of the mutation.

    Brown (Br)

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  • Descriptive terms in zebrafinch

    Descriptive terms for the zebra finch that will allow you to identify each area and discuss between breeder of the same "language".
    Open the article to have a large photo.

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