遗传学整理

Glossary for Medical Genetics

◆Allele: one of the alternative versions of a gene or DNA sequence at a given locus.

◆Allele-specific oligonucleotide (ASO): an oligonucleotide probe synthesized to match a particular DNA

sequence precisely and allow the discrimination of alleles than differ by only a single base.

◆Allelic heterogeneity: in a population, there may be a number of different mutant alleles at a single locus. In

an individual, the same or similar phenotype may be caused by different mutant alleles rather than by identical alleles at the locus. (血红蛋白基因突变)

◆Locus heterogeneity: the production of identical phenotypes by mutants at two or more different loci.(e.g.

Retinitis pigmentosa视网膜色素变性/先天性聋哑)

◆Amniocentesis：a procedure used in prenatal diagnosis to obtain amniotic fluid, which contains cells of fetal

origin that can be cultured for analysis. Amniotic fluid is withdrawn from the amniotic sac by syringe after insertion of a hollow needle into the amnion through the abdominal wall and uterine wall.

◆Aneuploidy: any chromosome number that is not an exact multiple of the haploid number. The common forms

of aneuploidy in humans are trisomy and monosomy.

◆Haploid: the chromosome number of normal gamete, with only one member of each chromosome pair. In

humans, the haploid number is 23.

◆Haploinsufficiency: a cause of genetic disease in which the contribution from a normal allele is insufficient to

prevent disease because of a loss-of –function mutation at the other allele.

◆Haplotype: a group of alleles in coupling at closely linked loci, usually inherited as a unit.

◆Hapmap: a set of haplotypes, defined by tag SNPs, distributed throughout the genome, used for association

studies.

◆Anticipation: the progressively earlier onset and increased severity of certain diseases in successive

generations of a family. Anticipation is caused by expansion of the number of unstable repeats within the gene responsible for the disease.

◆Heterochromatin：chromatin that stains darkly throughout the cell cycle, even in interphase generally thought

to be late replicating and genetically inactive. Satellite DNA in regions such as centromeres, acrocentric short arms, and 1qh, 9qh, 16qh, and Yqh constitutes constitutive hetertochromatin, whereas the chromatin of inactive X chromosome is referred to as facultative heterochromatin.

◆Antisense strand of DNA: the non-coding DNA strand, which is complementary to mRNA and serves as the

template for RNA synthesis. Also called the transcribed strand.

◆Association: in genetic epidemiology, describes the situation in which a particular allele is found either

significantly more or significantly less frequently in a group of affected individuals than would be expected from the frequency of allele in the general population from which the affected individuals were drawn.

◆Autosome: any nuclear chromosome other than the sex chromosomes;22 pairs in the human karyotype. A

disease caused by mutation in an Autosome gene or gene pair shows autosomal inheritance.

◆Balanced polymorphism: a polymorphism maintained in the population by heterozygote advantage, allowing

an allele, even one that is deleterious in the homozygous state, to persist at a relatively high frequency in the population.

◆Carrier: an individual heterozygous for a particular mutant allele. The term is used for heterozygote for

autosomal recessive alleles, for females heterozygous for X-linked alleles, or, less commonly, for an individual heterozygous for an autosomal dominant allele but not expressing it (e.g. a heterozygote for a Huntington disease allele in the pre-symptomatic stage).

◆Centromere: the primary constriction on the chromosome, a region at which the sister chromatids are held

together and at which the kinetochore is formed. Required for normal segregation in mitosis and meiosis.