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1、生物英语证书考试(PEC)-遗传学常用术语Achondroplasia - the most common and well known form of short limbed dwarfism characterized by a normal trunk size with disproportionally short arms and legs, and a disproportionally large head; autosomal dominant condition. Advanced maternal age - women over age 34 (age 35 at d
2、elivery) at increased risk for nondisjunction trisomy in fetus. Alcoholism - a chronic and progressive condition characterized by the inability to control the consumption of alcohol. Allele - an alternative form of a gene; any one of several mutational forms of a gene. Alpha-fetoprotein (AFP) - a pr
3、otein excreted by the fetus into the amniotic fluid and from there into the mothers bloodstream through the placenta. Alu repetitive sequence - the most common dispersed repeated DNA sequence in the human genome accounting for 5% of human DNA. The name is derived from the fact that these sequences a
4、re cleaved by the restriction endonuclease Alu. Amino acid sequence - the linear order of the amino acids in a protein or peptide. Amniocentesis - prenatal diagnosis method using cells in the amniotic fluid to determine the number and kind of chromosomes of the fetus and, when indicated, perform bio
5、chemical studies. Amniocyte - cells obtained by amniocentesis. Amplification - any process by which specific DNA sequences are replicated disproportionately greater than their representation in the parent molecules. Aneuploidy - state of having variant chromosome number (too many or too few). (i.e.
6、Down syndrome, Turner syndrome). Angelman syndrome - a condition characterized by severe mental deficiency, developmental delay and growth deficiency, puppet-like gait and frequent laughter unconnected to emotions of happiness. Apert syndrome - a condition caused by the premature closure of the sutu
7、res of the skull bones, resulting in an altered head shape, with webbed fingers and toes. Autosomal dominant. Artificial insemination - the placement of sperm into a female reproductive tract or the mixing of male and female gametes by other than natural means. Autosome - a nuclear chromosome other
8、than the X- and Y-chromosomes. Autoradiograph - a photographic picture showing the position of radioactive substances in tissues. Bacteriophage - a virus whose host is a bacterium; commonly called phage. Barr body - the condensed single X-chromosome seen in the nuclei of somatic cells of female mamm
9、als. base pair a pair of hydrogen-bonded nitrogenous bases (one purine and one pyrimidine) that join the component strands of the DNA double helix. Base sequence - a partnership of organic bases found in DNA and RNA; adenine forms a base pair with thymine (or uracil) and guanine with cytosine in a d
10、ouble-stranded nucleic acid molecule. Baysian analysis - a mathematical method to further refine recurrence risk taking into account other known factors. Becker muscular dystrophy - X-linked condition characterized by progressive muscle weakness and wasting; manifests later in life with progression
11、less severe than Duchenne muscular dystrophy. Carrier - an individual heterozygous for a single recessive gene. cDNA - complementary DNA produced from a RNA template by the action of RNA- dependent DNA polymerase. Centromere - a region of a chromosome to which spindle traction fibers attach during m
12、itosis and meiosis; the position of the centromere determines whether the chromosome is considered an acrocentric, metacentric or telomeric chromosome. Charcot-Marie Tooth disease - a condition characterized by degeneration of the motor and sensory nerves that control movement and feeling in the arm
13、 below the elbow and the leg below the knee; transmitted in autosomal dominant, autosomal recessive and X-linked forms. Chorionic villus sampling - an invasive prenatal diagnostic procedure involving removal of villi from the human chorion to obtain chromosomes and cell products for diagnosis of dis
14、orders in the human embryo. Chromosome - in the eukaryotic nucleus, one of the threadlike structures consisting of chromatin and carry genetic information arranged in a linear sequence. Chromosome banding - a technique for staining chromosomes so that bands appear in a unique pattern particular to t
15、he chromosome. Cleft lip/palate - congenital condition with cleft lip alone, or with cleft palate; cause is thought to be multifactorial. Clone - genetically engineered replicas of DNA sequences. Cloned DNA - any DNA fragment that passively replicates in the host organism after it has been joined to
16、 a cloning vector. Codon - a sequence of three nucleotides in mRNA that specifies an amino acid. Consanguinity - genetic relationship. Consanguineous individuals have at least one common ancestor in the preceding few generations. Conservative change - an amino acid change that does not affect significantly the function of the p
