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| A human genetic disorder resulting from the presence of an extra chromosomes 21; characterized by heart and respiratory defects and varying degrees of mental retardation |
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An accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail toseparate at anaphase.
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The loss of one or more nucleotides from a gene by mutation; the loss of fragment of a chromosome.
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Repetition of part of a chromosome resulting from fusion with a fragment from a homologous chromosome; can result from an error in meisosis or from mutagenesis
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A change in a chromosome resulting from reattachment of a chromosome fragment to the orginial chromosome, but in a reverse direction. Mutagens and errors during meiosis can cause this
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A change in a chromoome resulting from a chromosomal fragment attaching to a nonhomologous chromosome; can occur as a result of an error in meiosis or from mutagenesis
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An individual who is heterozygous for a recessively inherited disorder and who therefore does not show symptoms of that disorder
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A genetic disease that occurs in people with two copies of a certain recessive allele; characterized by an excessive secretion of mucus and vulnerability to infection; fatal if untreated
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A form of human dwarfism caused by a single dominant allele; the homozygous condition is lethal.
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| A human genetic disease caused by a dominant allele; charactierzed by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms |
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An age-related dementia (mental deterioration) characterized by confusion, memory loss and other symptoms.
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| A technique for diagnosing genetic defects while a fetus is in the uterus. A sample of amiotic fluid, obtained via a needle inserted into the amnion, is analyzed for telltale chemicals and defective fetal cells. |
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A technique for diagnosing genetic defects while the fetus is in the uterus. A small sample of the fetal portion of the placenta is removed and analyzed
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| A technique for examining a fetus in the uterus. High-frequency sound waves echoing off the fetus are used to produce an image of the fetus |
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The fusion of sperm and egg produced by the same individual organism.
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The fusion of sperm and egg derived from two different individuals.
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Crosses between identical homozygotes
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The offspring of parents of two different species or of two different varieties of one species; the offspring of two parents that differ in one or more inherited traits; an individual that is heterozygous for one or more pairs of genes
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An alternative form of gene
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| A discrete unit of heredity information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses). Most of eukaryote's are located in its chromosomal DNA; a few are carried by the DNA of mitochondria and chloroplasts |
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| The particular site where a gene is found on a chromosome. Homologous chromosomes have corresponding genes of these |
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In a heterozygote, the allele that determines the phenotype with respect to a partcular gene.
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In a heterozygous individual, the allele that has no noticeable effect on the phenotype.
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| Having two identical allelesfor a given gene. |
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Having two different alleles for a given gene.
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A diagram used in the study of inheritance to show the results of random fertilization
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| The genetic makeup of an organism. |
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The expressed traits of an organism.
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An experimental mating of individuals differing at one genetic locus.
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An experimental mating of individuals differing at two genetic loci.
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The mating between an individual of unknown genotype for a particular characteristic and an individual that is homozygous recessive for that same characteristic.
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A type of inheritance in which the phenotype of a heterozygote (Aa) is intermediate between the phenotypes of the two types of homozygoes (AA and aa)
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Inheritance pattern in which a heterozygote expresses the distince trait of both alleles
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The control of more than one phenotypic characteristic by a single gene
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The additive effect of two or more gene loci on a single phenotypic characteristic
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One gene suppresses or "dominates" a different gene rather than an allele
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A trait of female mammals due to inactivation of one X chromosome in every cell
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A trick for equalizing the "dose" of X genes in XX vs. XY individuals
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Genetic Recombination (Crossing Over) |
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| The production, by crossing over and/or independent assortment of chromosomes during meiosis, of offspring with allele comvinations different from those in the parents. The term may also be used more specifically to mean the production by crossing over of eukaryotic or prokaryotic chromosomes with gene combinations different from t hose in the original chromosomes. |
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Traits are inherited like particles = genes
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The parent individuals from which offspring are derived in studies of inheritance; stands for parental
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The offspring of two parental individuals; stands for first filial
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The offspring of the F1 generation; stands for second filial
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A chromosome that determines whether an individual is male or female
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A chromosome not directly involved in determining the sex of an organism; in mammals, any chromosome other than x or y
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| How sex-lined (X-chromosomes) genes are passed from Mom to son |
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The phenotype most commonly found in nature
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A change in the nucleotidesequence of DNA; the ultimate source of genetic diversity
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