Developmental Disorders of the Lymphatics

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Sunday, November 06, 2005

Genetics Glossary - Page Two

Parthenogenesis -- the development of an individual from an egg without fertilization. PCR -- polymerase chain reaction; a technique for copying the complementary strands of a target DNA molecule simultaneously for a series of cycles until the desired amount is obtained.

Pedigree -- a diagram of the heredity of a particular trait through many generations of a family.

Phenotype -- observable characteristics of an organism produced by the organism's genotype interacting with the environment.

Physical map -- map where the distance between markers is the actual distance, such as the number of base pairs.

PKU -- phenylketonuria, an enzyme deficiency condition characterized by the inability to convert one amino acid, phenylalanine, to another, tyrosine, resulting in mental deficiency. plasmid double-stranded, circular, bacterial DNA into which a fragment of DNA from another organism can be inserted.

Pleiotropy -- the phenomenon of variable phenotypes for a number of distinct and seemingly unrelated phenotypic effects.

Polycystic kidney disease (PKD) -- a group of conditions characterized by fluid filled sacs that slowly develop in both kidneys, eventually resulting in kidney malfunction.

Polymerase -- any enzyme that catalyzes the formation of DNA or RNA from deoxyribonucleotides or ribonucleotides.

Prader-Willi syndrome -- a condition characterized by obesity and insatiable appetite, mental deficiency, small genitals, and short stature. May be deletion of #15 chromosome.

Predisposition -- to have a tendency or inclination towards something in advance.

Presymptomatic diagnosis -- diagnosis of a genetic condition before the appearance of symptoms.

Primer -- nucleotides used in the polymerase chain reaction to initiate DNA synthesis at a particular location.

Probability -- the long term frequency of an event relative to all alternative events, and usually expressed as decimal fraction.

Proband -- individual in a family who brought the family to medical attention.

Probe -- single-stranded DNA labeled with radioactive isotopes or tagged in other ways for ease in identification.

Prognosis -- prediction of the course and probable outcome of a disease.

Proteus syndrome -- a condition characterized by distorted asymmetric growth of the body and enlarged head, enlarged feet, multiple nevi on the skin; mode of inheritance is unknown.

Public policy -- a set of action guidelines or rules that result from the actions or lack of actions of governmental entities.

Recessive -- a gene that is phenotypically manifest in the homozygous state but is masked in the presence of a dominant allele.

Recombination -- the natural process of breaking and rejoining DNA strands to produce new combinations of genes and, thus, generate genetic variation. Gene crossover during meiosis.

Repeat sequences -- the length of a nucleotide sequence that is repeated in a tandem cluster.

Retinitis pigmentosa -- group of hereditary ocular disorders with progressive retinal degeneration. Autosomal dominant, autosomal recessive, and x-linked forms.

Retinoblastoma -- a childhood malignant cancer of the retina of the eye. reverse transcriptase viral enzyme used to make cDNA.

RFLP -- restriction fragment length polymorphism; variations occurring within a species in the length of DNA fragments generated by a species endonuclease.

Ribosomal protein -- one of the ribonucleoprotein particles that are the sites of translation.

Rubinstein-Taybi syndrome -- condition with multiple congenital anomalies including: mental deficiency, broad thumbs, small head, broad nasal bridge and beaked nose.

Sanger sequence -- "plus and minus" or "primed synthesis" method; DNA is synthesized so it is radioactively labeled and the reaction terminates specifically at the position corresponding to a given base.

Selection -- the process of determining the relative share allotted individuals of different genotypes in the propagation of a population; the selective effect of a gene can be defined by the probability that carriers of the gene will reproduce.

Sex determination -- the mechanism in a given species by which sex is determined; in many species sex is determined at fertilization by the nature of the sperm that fertilizes the egg.

Sickle cell anemia -- an hereditary, chronic form of hemolytic anemia characterized by breakdown of the red blood cells; red blood cells undergo a reversible alteration in shape when the oxygen tension of the plasma falls slightly and a sickle-like shape forms.

Somatic cell hybrid -- hybrid cell line derived from two different species; contains a complete chromosomal complement of one species and a partial chromosomal complement of the other; human/hamster hybrids grow and divide, losing human chromosomes with each generation until they finally stabilize, the hybrid cell line established is then utilized to detect the presence of genes on the remaining human chromosome.

Somatic mutation -- a mutation occurring in any cell that is not destined to become a germ cell; if the mutant cell continues to divide, the individual will come to contain a patch of tissue of genotype different from the cells of the rest of the body.

Southern blotting -- a technique for transferring electrophoretically resolved DNA segments from an agarose gel to a nitrocellulose filter paper sheet via capillary action; the DNA segment of interest is probed with a radioactive, complementary nucleic acid, and its position is determined by autoradiography.

Spina bifida -- a congenital condition that results from altered fetal development of the spinal cord, part of the neural plate fails to join together and bone and muscle are unable to grow over this open section.

Syndrome -- a recognizable pattern or group of multiple signs, symptoms or malformations that characterize a particular condition; syndromes are thought to arise from a common origin and result from more than one developmental error during fetal growth.

Tay-Sachs disease -- a fatal degenerative disease of the nervous system due to a deficiency of hexosamidase A, causing mental deficiency, paralysis, mental deterioration, and blindness; found primarily but not exclusively among Ashkenazi Jews. Autosomal recessive. Teratogens -- any agent that raises the incidence of congenital malformations.

3' - end -- the end of a polynucleotide with a free (or phosphorylated) 3' - hydroxyl group.

Trait -- any detectable phenotypic property of an organism.

Transduction -- the transfer of bacterial genetic material from one bacterium to another using a phage as a vector.

Transferase -- enzymes that catalyze the transfer of functional groups between donor and acceptor molecules.

Transcription -- the formation of an RNA molecule upon a DNA template by complementary base pairing.

Translation -- the formation of a polypeptide chain in the specific amino acid sequence directed by the genetic information carried by mRNA.

Translocation -- a chromosome aberration which results in a change in position of a chromosomal segment within the genome, but does not change the total number of genes present.

Triplet code -- a code in which a given amino acid is specified by a set of three nucleotides.

Tumor suppressor gene -- genes that normally function to restrain the growth of tumors; the best understood case is for hereditary retinoblastoma.

Transgenic organism -- one into which a cloned genetic material has been experimentally transferred, a subset of these foreign gene express themselves in their offspring.Turner syndrome a chromosomal condition in females (usually 45,XO) due to monosomy of the X- chromosome; characterized by short stature, failure to develop secondary sex characteristics, and infertility.

UNESCO -- United Nations Educational, Scientific, and Cultural Organization.

VNTR -- variable number tandem repeats; any gene whose alleles contain different numbers of tandemly repeated oligonucleotide sequences.

Vector -- a self-replicating DNA molecule that transfers a DNA segment between host cells.

Von Hippel-Lindau syndrome -- an autosomal dominant condition characterized by the anomalous growth and proliferation of blood vessels on the retina of the eye and the cerebellum of the brain; cysts and cancers in the kidneys, pancreas, and adrenal glands.

Western blotting analysis -- a technique used to identify a specific protein; the probe is a radioactively labeled antibody raised against the protein in question.

X-inactivation -- the repression of one of the two X-chromosomes in the somatic cells of females as a method of dosage compensation; at an early embryonic stage in the normal female, one of the two X-chromosomes undergoes inactivation, apparently at random, from this point on all descendent cells will have the same X-chromosome inactivated as the cell from which they arose, thus a female is a mosaic composed of two types of cells, one which expresses only the paternal X-chromosome, and another which expresses only the maternal X-chromosome.

XYY syndrome -- genetic condition in males with extra Y chromosome (in 1 in 1000 male births). Symptoms: tall stature (over 6'), may including sterility, developmental delay, learning problems.

YAC -- yeast artificial chromosome; a linear vector into which a large fragment of DNA can be inserted; the development of YAC's in 1987 has increased the number of nucleotides which can be cloned.

Zoo blot -- northern analysis of mRNA from different organisms.

Genetics Education Center - U of Kansas

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Lymphedema People

Lymphedema Glossary

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Additional Resources:

A Genetics Glossary

Microbial Genetics Glossary

A Hypermedia Glossary of Genetic Terms


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