Genetic Basics
© Eddie’s Aviary – reproduce only with permission please
When considering breeding Linnies, learning how to identify the mutations properly, understanding basic genetics (click here for the post on Genetic Inheritance), and Proper Pairing Protocols should be your first step. First are basic genetic definitions, then how each mutation inherits is in the sticky found here, Linnie Genetic Inheritance Explained (dominant, recessive, sex-linked, incomplete dominant, etc.) If it seems overwhelming, start with Dominant and Recessive definitions, if that clicks, start from the beginning. Genetics can take time to fully comprehend, so we recommend coming back and reading this and asking questions until it sinks in.
WHAT IS A CHROMOSOME?: a chromosome is a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
WHAT IS AN ALLELE?: an allele is one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
WHAT IS GENOTYPE?: genotype is the genetic constitution (make up) of an individual organism.
WHAT IS PHENOTYPE?: the set of observable (visual) characteristics of an individual resulting from the interaction of its genotype (genetic make up) with the environment.
WHAT IS A TRAIT?: In biology, a trait or character is a feature of an organism. The term phenotype is sometimes used as a synonym for trait in common use, but strictly speaking, does not indicate the trait, but the state of that trait (e.g., the trait eye color has the phenotypes blue, brown and hazel)
WHAT IS A MUTATION?: A mutation is a spontaneous change to the DNA in a gene during the formation of ova and sperm. Offspring received an altered gene that neither parent had, and passes this mutated gene to its young. Sometimes mutations are genetic failures, but in this case we are talking about the rarely dangerous (when paired correctly) color mutation. Humans work hard to develop these color mutations in birds for our own viewing pleasure. In the wild, mutations of feather color can occur as well, but those specimens are either killed off as the color is not conducive to finding a mate, or are lost to predation because blending with the environment color was not possible. So in the wild, these mutations get bred out and the wild type (normal green in this case) prevails.
Mutations can eliminate or modify feather pigment or change its feather structure so it reflects light in a different way. Humans have one type of pigment (also called melanin) but our avian friends have two or more! Dark colors such as brown, black or grey in birds are melanin colors. The pigments found in birds are melanin, carotenoids (also called psittacins) (red, yellow, and orange feathers have this different type of pigment) and porphyrins (green). Green or Blue seen in most hookbills is an optical illusion, it is not caused by actual added pigment to the feathers, it is because light reflects off the mutated structures in the feathers that have melanin in them.
WHAT IS HETEROGAMATIC SEX?: Heterogametic sex refers to the sex of a species in which the sex chromosomes are not the same. For example, in humans, males, with an X and a Y sex chromosome, would be referred to as the heterogametic sex, and females having two X sex chromosomes would be referred to as the homogametic sex. In Birds, this is the opposite (and birds have ZW instead of XY chromosomes) – the females are the heterogametic (sex determining) parent in the pair.
WHY DO BIRDS HAVE ZW INSTEAD OF XY CHROMOSOMES?: Birds, butterflies, and snakes take everything we know about sex at the chromosomal level and stand it on its head. Instead of X and Y chromosomes, they have Z and W chromosomes. The XY and ZW chromosomes share no genes at all. The ZW chromosomes flip the sex determination system. A Linnie cock bird has a ZZ chromosome. A female has a ZW chromosome. In contrast to the XY sex-determination system, where the sperm determines the sex, in the ZW system, the ovum determines the sex of the offspring. Males are the homogametic sex (ZZ), while females are the heterogametic sex (ZW). The Z chromosome is larger and has more genes, like the X chromosome in the human XY system. This is the chromosome sex linked genes ride on. The W chromosome does not carry genes for color (mutation).
WHAT IS A “SPLIT” GENE?: You may hear a bird is “split” to another gene that the bird does not express visually. This is because the gene may be recessive, or sex-linked and riding on a hidden chromosome. In the Lineolated parakeet, females can only be split to turquoise. Males can be split to ino (sex linked) or turquoise.
DOMINANT GENES: A dominant gene is a segment of DNA information that is used to make chromosomes. Dominant genes are a result of dominant alleles in chromosomes. When an allele is dominant it is expressed in the phenotype (visual) over a recessive allele.
RECESSIVE GENES: A recessive gene is a gene that can be masked by a dominant gene. In order to have a trait that is expressed by a recessive gene, such as blue eyes, you must get the gene for blue eyes from both of your parents. ... A recessive allele must team up with another recessive allele in order to show up visually (phenotypically).
SEX-LINKED (SL) GENES: In birds, it is the male that has two copies of every gene, while the female has only one copy of the genes on the sex chromosomes. The W-chromosome is small with few genes. But the Z-chromosome has many sex-linked genes, including genes that control feather color and color intensity. The Z chromosome is found only in males, hence their ability to hide “splits” where females would express them phenotypically (visually) if the gene is present.
Be sure to check the next sticky on Linnie Genetic Inheritance Explained, and Genetic Inheritance for how these definitions are applied to the Lineolated Parakeet in an easy, but in-depth understand way. If you have ANY questions about any of the information above, please start a thread to receive answers. It is always best to be armed with a good understanding of what you are doing BEFORE starting, or you will undoubtedly be scrambling later to re-pair by purchasing new mates.
If you enjoy this Forum, or the Content found here helpful.... consider buying the author a coffee. Helps with website costs, and keeps motivation levels up for more late night work. Thank you
CLICK HERE to Buy Me A Coffee
© Eddie’s Aviary – reproduce only with permission please
When considering breeding Linnies, learning how to identify the mutations properly, understanding basic genetics (click here for the post on Genetic Inheritance), and Proper Pairing Protocols should be your first step. First are basic genetic definitions, then how each mutation inherits is in the sticky found here, Linnie Genetic Inheritance Explained (dominant, recessive, sex-linked, incomplete dominant, etc.) If it seems overwhelming, start with Dominant and Recessive definitions, if that clicks, start from the beginning. Genetics can take time to fully comprehend, so we recommend coming back and reading this and asking questions until it sinks in.
WHAT IS A CHROMOSOME?: a chromosome is a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
WHAT IS AN ALLELE?: an allele is one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
WHAT IS GENOTYPE?: genotype is the genetic constitution (make up) of an individual organism.
WHAT IS PHENOTYPE?: the set of observable (visual) characteristics of an individual resulting from the interaction of its genotype (genetic make up) with the environment.
WHAT IS A TRAIT?: In biology, a trait or character is a feature of an organism. The term phenotype is sometimes used as a synonym for trait in common use, but strictly speaking, does not indicate the trait, but the state of that trait (e.g., the trait eye color has the phenotypes blue, brown and hazel)
WHAT IS A MUTATION?: A mutation is a spontaneous change to the DNA in a gene during the formation of ova and sperm. Offspring received an altered gene that neither parent had, and passes this mutated gene to its young. Sometimes mutations are genetic failures, but in this case we are talking about the rarely dangerous (when paired correctly) color mutation. Humans work hard to develop these color mutations in birds for our own viewing pleasure. In the wild, mutations of feather color can occur as well, but those specimens are either killed off as the color is not conducive to finding a mate, or are lost to predation because blending with the environment color was not possible. So in the wild, these mutations get bred out and the wild type (normal green in this case) prevails.
Mutations can eliminate or modify feather pigment or change its feather structure so it reflects light in a different way. Humans have one type of pigment (also called melanin) but our avian friends have two or more! Dark colors such as brown, black or grey in birds are melanin colors. The pigments found in birds are melanin, carotenoids (also called psittacins) (red, yellow, and orange feathers have this different type of pigment) and porphyrins (green). Green or Blue seen in most hookbills is an optical illusion, it is not caused by actual added pigment to the feathers, it is because light reflects off the mutated structures in the feathers that have melanin in them.
WHAT IS HETEROGAMATIC SEX?: Heterogametic sex refers to the sex of a species in which the sex chromosomes are not the same. For example, in humans, males, with an X and a Y sex chromosome, would be referred to as the heterogametic sex, and females having two X sex chromosomes would be referred to as the homogametic sex. In Birds, this is the opposite (and birds have ZW instead of XY chromosomes) – the females are the heterogametic (sex determining) parent in the pair.
WHY DO BIRDS HAVE ZW INSTEAD OF XY CHROMOSOMES?: Birds, butterflies, and snakes take everything we know about sex at the chromosomal level and stand it on its head. Instead of X and Y chromosomes, they have Z and W chromosomes. The XY and ZW chromosomes share no genes at all. The ZW chromosomes flip the sex determination system. A Linnie cock bird has a ZZ chromosome. A female has a ZW chromosome. In contrast to the XY sex-determination system, where the sperm determines the sex, in the ZW system, the ovum determines the sex of the offspring. Males are the homogametic sex (ZZ), while females are the heterogametic sex (ZW). The Z chromosome is larger and has more genes, like the X chromosome in the human XY system. This is the chromosome sex linked genes ride on. The W chromosome does not carry genes for color (mutation).
WHAT IS A “SPLIT” GENE?: You may hear a bird is “split” to another gene that the bird does not express visually. This is because the gene may be recessive, or sex-linked and riding on a hidden chromosome. In the Lineolated parakeet, females can only be split to turquoise. Males can be split to ino (sex linked) or turquoise.
DOMINANT GENES: A dominant gene is a segment of DNA information that is used to make chromosomes. Dominant genes are a result of dominant alleles in chromosomes. When an allele is dominant it is expressed in the phenotype (visual) over a recessive allele.
RECESSIVE GENES: A recessive gene is a gene that can be masked by a dominant gene. In order to have a trait that is expressed by a recessive gene, such as blue eyes, you must get the gene for blue eyes from both of your parents. ... A recessive allele must team up with another recessive allele in order to show up visually (phenotypically).
SEX-LINKED (SL) GENES: In birds, it is the male that has two copies of every gene, while the female has only one copy of the genes on the sex chromosomes. The W-chromosome is small with few genes. But the Z-chromosome has many sex-linked genes, including genes that control feather color and color intensity. The Z chromosome is found only in males, hence their ability to hide “splits” where females would express them phenotypically (visually) if the gene is present.
Be sure to check the next sticky on Linnie Genetic Inheritance Explained, and Genetic Inheritance for how these definitions are applied to the Lineolated Parakeet in an easy, but in-depth understand way. If you have ANY questions about any of the information above, please start a thread to receive answers. It is always best to be armed with a good understanding of what you are doing BEFORE starting, or you will undoubtedly be scrambling later to re-pair by purchasing new mates.
If you enjoy this Forum, or the Content found here helpful.... consider buying the author a coffee. Helps with website costs, and keeps motivation levels up for more late night work. Thank you
CLICK HERE to Buy Me A Coffee