Mechanisms Of Genetic Control

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Gene - written

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All caps and italicized
Numeric designations are on same line.
Superscript letters are lower case.

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Antigen - written

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Single letter: letter with + or -
Superscript: use parantheses Fy(a+)
Numeric: Cap letter colon number K:1 if pos; K:-1 if neg
HLA: number follows letter denoting series HLA-A1

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Gene: A unit of inheritance within a chromsome

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Phenotype

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The outward expression of genes. On blood cells, serologically demonstrable antigens constitute the phenotype (except those sugar sites that are determined by transferases)

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Genotype

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An individual's genetic makeup

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Allele

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One of two or more genes on the same chromosome of an homologous pair. Example: A, B, O

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Cis - The location of two or more genes on the same chromosome of a homologous pair.

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Trans - The location of two or more genes on opposite chromosomes of a homologous pair.

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Amorph - define

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A gene that does not appear to produce a detectable antigen; a silent gene such as Jk, Lu, O

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Homozygous

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possessing a pair of identical alleles

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Heterozygous

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possessing different alleles at a given gene locus

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Hemizygous

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an individual who has only one member of a chromosome pair or chromosome segment rather than the usual two; refers in particular to X-linked genes in males who under normal circumstances have only one X chromosome

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Mitosis - define

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The process where a single somatic cell divides resulting in generally two identical diploid cells, each containing the same number of chromosomes and genetic content as that of the original cell.

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Mitosis - list phases

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Prophase, Metaphase, Anaphase, Telophase

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Polymorphic

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Having two or more alleles at a given locus. Example: ABO system, HLA system

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Co-dominant

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Equal expression of both traits, most BGS have this inheritance

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Dominant

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Gene product expressed over another gene, only one copy of gene is needed for expression

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Recessive

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Observable product only when not paired with dominant allele, two copies are needed for expression

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Trait appears in every generation with no "skipping"

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Autosomal Dominant

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Trait is transmitted by an affected person to approximately half of his children

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Autosomal Dominant

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Unaffected persons do not transmit the trait to their children

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Autosomal Dominant

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The occurrence and transmission of the trait are not influenced by sex

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Autosomal Dominant or Autosomal Recessive

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Trait characteristically appears only in sibs, not in parents, offspring or other relatives; skips generations

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Autosomal Recessive

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On average, 25% of sibs of the propositus are affected.

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Autosomal Recessive

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Parents of the child with trait may be consanguineous

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Autosomal Recessive

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Absence of father to son transmission

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Sex-Linked Dominant and Sex-Linked Recessive: X-Linked

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All daughters of a man expressing trait possess the allele and express the trait

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Sex-Linked Dominant

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Children of heterozygous woman expressing the trait will have 50% chance of inheriting the allele

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Sex-Linked Dominant

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All children of a homozygous woman express trait

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Sex-Linked Dominant

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Offspring of affected males used to determine inheritance

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Sex-Linked Dominant

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Incidence in males is much higher than in females

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Sex-Linked Recessive: X-Linked

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Trait is passed from an affected man to all of his daughters to half of their sons

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Sex-Linked Recessive: X-Linked

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Trait is transmitted only from father to son

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Sex-Linked Recessive: Y-Linked

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Mendel's First Law

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Independent Segregation: 1. Passing of one gene from each parent to offspring 2. Hereditary characteristics are determined by particulate units or factors.

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Mendel's Second Law

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Independent Assortment: 1. Random behavior of genes on separate chromosomes during mitosis and meiosis that results in a mixture of genetic material in the offspring.

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Direct Exclusion of Paternity

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Genetic marker present in the child but is absent from the mother and the alleged father

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Indirect Exclusion of Paternity

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Child lacks genetic marker that alleged father must transmit to his offspring.