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Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph. In order to be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population (one with random mating).
Polymorphism is common in nature; it is related to biodiversity, genetic variation and adaptation; it usually functions to retain variety of form in a population living in a varied environment. The most common example is sexual dimorphism, which occurs in many organisms. Other examples are mimetic forms of butterflies (see mimicry), and human hemoglobin and blood types. |
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| allele is one of two or more forms of a gene or a genetic locus (generally a group of genes). The form "allel" is also used, an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation. However, many variations at the genetic level result in little or no observable variation. |
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The genotype is the genetic makeup of a cell, an organism, or an individual (i.e. the specific allele makeup of the individual) usually with reference to a specific character under consideration.[1] For instance, the human CFTR gene, which encodes a protein that transports chloride ions across cell membranes, can be dominant (A) as the normal version of the gene, or recessive (a) as a mutated version of the gene. Individuals receiving two recessive alleles will be diagnosed with Cystic fibrosis. It is generally accepted that inherited genotype, transmitted epigenetic factors, and non-hereditary environmental variation contribute to the phenotype of an individual.
Non-hereditary DNA mutations are not classically understood as representing the individual's genotype. Hence, scientists and physicians sometimes talk for example about the (geno)type of a particular cancer, that is the genotype of the disease as distinct from the diseased. |
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A phenotype (from Greek phainein, 'to show' + typos, 'type') is the composite of an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, phenology, behavior, and products of behavior (such as a bird's nest). Phenotypes result from the expression of an organism's genes as well as the influence of environmental factors and the interactions between the two.
The genotype of an organism is the inherited instructions it carries within its genetic code. Not all organisms with the same genotype look or act the same way because appearance and behavior are modified by environmental and developmental conditions. Likewise, not all organisms that look alike necessarily have the same genotype.
This genotype-phenotype distinction was proposed by Wilhelm Johannsen in 1911 to make clear the difference between an organism's heredity and what that heredity produces.[1][2] The distinction is similar to that proposed by August Weismann, who distinguished between germ plasm (heredity) and somatic cells (the body). The Genotype-Phenotype concept should not be confused with Francis Crick's central dogma of molecular biology, which is a statement about the directionality of molecular sequential information flowing from DNA to protein (but which cannot become transferred from proteins). |
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| Two a allele variants, so six genotypes |
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| Any individual has one of six possible genotypes (AA, AO, BB, BO, AB, and OO) that produce one of four possible phenotypes: "A" (produced by AA homozygous and AO heterozygous genotypes), "B" (produced by BB homozygous and BO heterozygous genotypes), "AB" heterozygotes, and "O" homozygotes. It is now known that each of the A, B, and O alleles is actually a class of multiple alleles with different DNA sequences that produce proteins with identical properties: more than 70 alleles are known at the ABO locus.[4] An individual with "Type A" blood may be an AO heterozygote, an AA homozygote, or an A'A heterozygote with two different 'A' alleles. |
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"recessive gene" refers to an allele that causes a phenotype (visible or detectable characteristic) that is only seen in a homozygous genotype (an organism that has two copies of the same allele) and never in a heterozygous genotype. Every person has two copies of every gene on autosomal chromosomes, one from mother and one from father. If a genetic trait is recessive, a person needs to inherit two copies of the gene for the trait to be expressed. Thus, both parents have to be carriers of a recessive trait in order for a child to express that trait. If both parents are carriers, there is a 25% chance with each child to show the recessive trait. Thus if the parents are closely related (in-breeding) the probability of both having inherited the same gene is increased and as a result the probability of the children showing the recessive trait is increased as well.
The term "recessive gene" is part of the laws of Mendelian inheritance created by Gregor Mendel. Examples of recessive genes in Mendel's famous pea plant experiments include those that determine the color and shape of seed pods, and plant height. |
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| genetics is a relationship between alleles of a gene, in which one allele masks the expression (phenotype) of another allele at the same locus. In the simplest case, where a gene exists in two allelic forms (designated A & B), three combinations of alleles (genotypes) are possible: AA, AB, and BB. If AA and BB individuals (homozygotes) show different forms of the trait (phenotype), and AB individuals (heterozygotes) show the same phenotype as AA individuals, then allele A is said to dominate or be dominant to or show dominance to allele B, and B is said to be recessive to A. If instead AB has the same phenotype as BB, B is dominant to A. |
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Genetics Of or relating to two alleles of a gene pair in a heterozygote that are both fully expressed.
2.
a. Ecology Being one of two or more of the most characteristic species in a biotic community.
b. Influencing the presence and type of other species in the community. |
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| an antigen is a substance that evokes the production of one or more antibodies. Each antibody binds to a specific antigen by way of an interaction similar to the fit between a lock and a key. The substance may be from the external environment or formed within the body. The immune system will try to destroy or neutralize any antigen that is recognized as a foreign and potentially harmful invader. The term originally came from antibody generator[1][2] and was a molecule that binds specifically to an antibody, but the term now also refers to any molecule or molecular fragment that can be bound by a major histocompatibility complex (MHC) and presented to a T-cell receptor.[3] "Self" antigens are usually tolerated by the immune system; whereas "Non-self" antigens can be identified as invaders and can be attacked by the immune system. |
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| Hh is a rare blood group also called Bombay Blood group. This blood phenotype was first discovered in Bombay, now known as Mumbai, in India, by Dr. Y.M. Bhende in 1952.The H antigen is an essential precursor to the ABO blood group antigens. The H locus is located on chromosome 19. It contains 3 exons that span more than 5 kb of genomic DNA, and it encodes a fucosyltransferase that produces the H antigen on RBCs. The H antigen is a carbohydrate sequence with carbohydrates linked mainly to protein (with a minor fraction attached to ceramide moiety). It consists of a chain of β-D-galactose, β-D-N-acetylglucosamine, β-D-galactose, and 2-linked, α-L-fucose, the chain being attached to the protein or ceramide. |
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| An antibody, also known as an immunoglobulin, is a large Y-shaped protein produced by B-cells that is used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, called an antigen.[1][2] Each tip of the "Y" of an antibody contains a paratope (a structure analogous to a lock) that is specific for one particular epitope (similarly analogous to a key) on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly (for example, by blocking a part of a microbe that is essential for its invasion and survival). The production of antibodies is the main function of the humoral immune system.[3] |
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| At one time, type O negative blood was considered the universal blood donor type. This implied that anyone — regardless of blood type — could receive type O negative blood without risking a transfusion reaction. |
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| Universal recipient are those with type AB Rh D positive blood are called universal recipients |
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| Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis |
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| Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis,[1] is an alloimmune condition that develops in a fetus, when the IgG molecules (one of the five main types of antibodies) produced by the mother pass through the placenta. Among these antibodies are some which attack the red blood cells in the fetal circulation; the red cells are broken down and the fetus can develop reticulocytosis and anemia. This fetal disease ranges from mild to very severe, and fetal death from heart failure (hydrops fetalis) can occur. When the disease is moderate or severe, many erythroblasts are present in the fetal blood and so these forms of the disease can be called erythroblastosis fetalis (or erythroblastosis foetalis). |
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Mother/fetal incompatibility:
• Overall ABO frequencies for:
• O allele 62.3%
• A allele 21.5% (15-30%)
• B allele 16% (10 – 20%)
Births from Type-O mothers
• If the father is type A or B or AB
o Overall fewer children produced than expected
• If father is heterozygous AO or BO, fewer children produced & greater number of OO kids than expected
• If father is type A, fewer type A children produced than if mother is A & father is O
Differential miscarriage rates:
• Often before pregnancy recognized
• Ex: one study: 12% of newborns of type O mothers were A or B (0.5%) had signs of blood distruction
Maternal blood crosses fetal blood system
• Anti-A & anti-B antibodies…
o This over time can change the frequencies of blood types |
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| Maternal-fetal incompatibility |
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Definition
Mother/fetal incompatibility:
• Overall ABO frequencies for:
• O allele 62.3%
• A allele 21.5% (15-30%)
• B allele 16% (10 – 20%)
Births from Type-O mothers
• If the father is type A or B or AB
o Overall fewer children produced than expected
• If father is heterozygous AO or BO, fewer children produced & greater number of OO kids than expected
• If father is type A, fewer type A children produced than if mother is A & father is O |
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| Prezygotic isolation - A type of reproductive isolation that occurs before the formation of a zygote can take place. In most cases mating does not even occur. Forms of prezygotic isolation include spatial, behavioral, mechanical and temporal isolation. Part of reproductive isolation. |
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| Worldwide allele frequencies for ABO (approx) |
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| Where A, B, O blood frequencies higher/lower (in general) |
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| Chronic disease association with blood type, examples |
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