DNA
Deoxyribonucleic acid (abbreviated DNA) is the molecule that carries genetic information for the development and functioning of an organism. DNA is made of two linked strands that wind around each other to resemble a twisted ladder — a shape known as a double helix.
DNA
https://www.genome.gov/genetics-glossary/genotype
Genotype
A score represents the type of variant found at a specific spot in the genome. It can be shown with symbols. Genotypes can also be expressed as the actual DNA sequence at that spot. Some genotypes affect an individual's visible traits, known as the phenotype.
https://www.britannica.com/science/phenotype
Phenotype
All the observable traits of an organism that result from the interaction of its genotype (complete genetic inheritance) with the environment. Examples of observable traits include behavior, biochemical properties, color, shape, and size.
https://www.genome.gov/genetics-glossary/Inherited
Inheritance
Inheritance in genetics refers to traits encoded in DNA and passed from parent to offspring during reproduction, following Mendelian genetics principles. These principles, established by Gregor Mendel in the 19th century through experiments with pea plants, describe how traits like color and shape are transferred across generations, introducing concepts of dominant and recessive inheritance.
https://www.genome.gov/genetics-glossary/Pedigree
Pedigree
A pedigree, in genetics, is a chart that diagrams the inheritance of traits or health conditions across generations of a family. It shows family relationships and indicates which individuals have the traits of interest. This graphic representation helps assess family connections, such as parent, sibling, or cousin. A pedigree can also help determine how traits or conditions are passed down through generations.
https://www.genome.gov/genetics-glossary/Epistasis
Epistasis
Epistasis is a phenomenon where the expression of one gene is modified (e.g., masked, inhibited, or suppressed) by the expression of one or more other genes. Interestingly, the term “epistasis” is derived from Greek roots meaning “standing upon.” A good example of epistasis can be seen in the coat color of the popular dog breed, the Labrador retriever. The coat color genes for Labrador retrievers are limited to black or chocolate. However, yellow Labrador retrievers can often be seen in dog parks. This occurs when recessive epistatic genes known as “extension genes” prevent color pigments from reaching the fur.
https://www.genome.gov/genetics-glossary/Dominant
Dominant
In genetics, this term describes the connection between a visible trait and the inherited gene versions. Individuals receive two alleles from their parents. For a dominant trait, only one dominant allele is needed to show the trait, while the recessive allele stays hidden. Generally, a person with two dominant alleles shows the same trait as someone with just one. However, a recessive trait needs both alleles to be present to be expressed.
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/incomplete-dominance
Incomplete Dominant
Incomplete dominance occurs when two parents each contribute unique genes, resulting in offspring with an intermediate appearance. This phenomenon is also referred to as semi-dominance or partial dominance. Mendel recognized dominance but not incomplete dominance. If he had studied Mirabilis jalapa instead of peas, he would have observed that the cross between a red-flowered plant and a white-flowered one produces all pink-flowered offspring, which represent the intermediate state. A heterozygous individual has two different alleles but may not always exhibit an intermediate appearance.
https://www.genome.gov/genetics-glossary/Codominance
Co Dominant
Codominance, in the context of genetics, refers to a type of inheritance where two versions (alleles) of the same gene are expressed simultaneously, resulting in different traits in an individual. In this scenario, neither trait is dominant over the other; rather, both traits are visible, such as in a plant or animal exhibiting more than one pigment color. For example, when a white flower is crossed with a red flower, the resulting F1 generation displays both white and red petals. Both traits are expressed distinctly. (see incomplete dominance)
https://www.genome.gov/genetics-glossary/Recessive-Traits-Alleles
Recessive
In genetics, this refers to how an observable trait is connected to the two versions of a gene that determine that trait. Individuals inherit two versions of each gene, known as alleles, from their parents. For a recessive trait to be expressed, both alleles of the gene must be identical and both must be present. If someone has only one of the recessive alleles, the trait will not be visible. This differs from a dominant trait, which requires just one of the two alleles to be expressed.
https://www.genome.gov/genetics-glossary/Polygenic-Trait
Polygenic
A trait, such as height or skin color, that is influenced by multiple genes. Because many genes contribute, polygenic traits do not adhere to simple inheritance patterns. These traits can also be affected by environmental factors, making them multifactorial.
https://pmc.ncbi.nlm.nih.gov/articles/PMC2679206/
XY and ZW Chromosomes
In XY and ZW systems, the sex chromosomes are not equivalent because one of them fails to pair correctly and accumulates harmful mutations. In the XY system, this is the Y chromosome that deteriorates; in the ZW system, it is the W chromosome. Currently, the mammalian X chromosome contains over three times as many genes as the Y, while the chicken Z chromosome has over ten times more than the W.
https://www.genome.gov/genetics-glossary/homologous-recombination
Homologous Recombination
Genetic recombination occurs when DNA sequences are exchanged between similar DNA molecules. During meiosis, homologous chromosomes from parents align, facilitating the exchange of comparable DNA sequences. This process serves as a crucial source of genetic variation in offspring.
https://pmc.ncbi.nlm.nih.gov/articles/PMC10712277/
Chromatophores
Vertebrate coloration arises from pigments, special structures, and interactions among three types of color cells known as chromatophores. Mammals and birds possess melanocytes, which produce brown melanin. In contrast, reptiles and cold-blooded vertebrates contain melanophores for melanin, alongside xanthophores, which hold white, yellow, and red pigments, and iridophores, which reflect light through guanine crystals to create colors.
https://medlineplus.gov/download/genetics/gene/tyr.pdf
Tyrosinase
The TYR gene gives instructions for the enzyme tyrosinase, which is found in melanocytes and helps produce melanin. Melanin colors the skin, hair, and eyes, and is essential for vision in the retina.
Tyrosinase starts melanin production by changing the amino acid tyrosine into dopaquinone, which is then converted into melanin in the skin, hair follicles, iris, and retina.
https://www.ncbi.nlm.nih.gov/gtr/conditions/C0078918/
Oculocutaneous Albinism, OCA
Researchers have identified various types of oculocutaneous albinism, distinguished by changes in skin, hair, and eye color, as well as genetic causes. Type 1 features white hair, very pale skin, and light-colored irises. Type 2 is milder, with creamy white skin and light yellow to light brown hair. Type 3, known as rufous oculocutaneous albinism, affects individuals with darker skin, presenting reddish-brown skin, ginger or red hair, and hazel or brown irises, and often has milder vision issues. Type 4 shows symptoms similar to type 2.
https://www.ncbi.nlm.nih.gov/gtr/conditions/C0268495/
T-/T+, Tyrosinase Negative/Positive, OCA Type IA/IB
Tyrosinase-positive oculocutaneous albinism is a genetically heterogeneous disorder characterized by decreased pigmentation in hair, skin, and eyes. 'Albinism' includes ocular changes due to reduced melanin, crucial for diagnosis. Although OCA caused by TYR gene mutations was traditionally called 'tyrosinase-negative,' some 'tyrosinase-positive' patients may have TYR mutations with residual enzyme activity, classifying them as OCA1B. Oculocutaneous Albinism OCA1, caused by TYR mutations, is divided into two types: type IA (OCA1A), with a complete lack of tyrosinase activity, and type IB (OCA1B), with reduced activity.
https://www.ncbi.nlm.nih.gov/medgen/338324
Hypopigmentation, OCA Type IV
Oculocutaneous albinism type IV (OCA4) is a genetic condition that affects the pigmentation of skin, hair, and eyes. The degree of pigmentation can vary from mild to severe. Hair color can range from white to yellow, blonde, or brown, with gray, blue-gray, or brown eyes. Other eye issues may include poor vision, underdeveloped macula, optic nerve abnormalities, or unusual blood vessels in the eye (Rundshagen et al., 2004).
Hyperpigmentation
https://www.genome.gov/genetics-glossary/heterozygous
Heterozygous
Heterozygosity in genetics means having different versions (alleles) of a gene from each parent. A person who is heterozygous for a gene has two different versions of that gene. On the other hand, a person who is homozygous for a gene has two identical versions of that gene.
https://www.genome.gov/genetics-glossary/homozygous
Homozygous
In genetics, the term means having the same versions (alleles) of a genetic marker from both parents. Therefore, a person who is homozygous for a genetic marker has two identical versions of that marker. In comparison, a person who is heterozygous for a marker has two different versions of that marker.