Kamus Demografi Pelbagai Bahasa, Edisi Kedua, Volum Bahasa Malaysia

Penolak tuntutan : Penaja Demopaedia tidak semestinya bersetuju dengan kesemua definisi yang terkandung dalam Kamus versi ini. Pengharmonian edisi kedua Kamus Demografi Pelbagai Bahasa adalah suatu proses berterusan. Sila rujuk laman perbincangan untuk komen selanjutnya.

910

Dalam eugenik¹, disiplin yang mencari jalan untuk meningkat kualiti hidup penduduk, penekanan diberikan kepada peranan keturunan², perpindahan ciri keturunan³, seperti warna mata, dari satu generasi ke generasi lain. Ciri yang diperoleh ⁴ tidak di pindah. Ciri maut⁵ amnya membawa kematian awal janin.

• 1. Eugenik, n. - eugenik, adj. - eugenik, n.: a pakar eugenik.
• 2. keturunan, n. - keturunan, adj.

911

The transmission of hereditary characteristics operates through genes¹ which are transmitted to children by their parents. Genetics² is the science concerned with the transmission and effects of hereditary factors. The genes are carried by chromosomes³ which are long filaments of DNA (deoxyribonucleic acid) located in the cell’s nucleus. The position of a gene on a chromosome is called its locus⁴. Genes occupying the same locus affect the same characteristic, although they do so in various ways which correspond to various alleles⁵ of the gene in this locus. The new cell formed by the union of two sexual cells or gametes⁶ during the process of conception (602-1) is called a zygote⁷.

• 1. All of the genes carried by an individual are collectively called his or her genetic endowment
• 2. Genetics, n. - genetic, adj. - geneticist, n.: a specialist in genetics.

912

The set of two genes of an individual at the same locus is called a genotype¹; the genotype is said to be homozygous² if the alleles are identical at a given locus; it is said to be heterozygous³ in the opposite case. The phenotype⁴ consists in the observable characteristics as determined by the genotype and the environment. If an heterozygous individual (AA’) cannot be distinguished from an homozygous individual (AA), the allele A is said to be dominant⁵ over allele A’, and A’ is said to be recessive⁶. Genes are subject to sudden and apparently random changes, called mutations⁷. Panmixia⁸ or random mating⁸ insures uniform distribution of genes within populations.

• 7. Mutation, n. - mutant, adj. or n.

913

A distinction is frequently made in eugenic policy between positive eugenics¹, aimed at increasing the number of persons believed to have desirable characteristics, and negative eugenics² aimed at restricting the reproduction of persons expected to transmit undesirable characteristics or hereditary defects³. Much attention has been given to the discussion of eugenic sterilization⁴, i.e., the sterilization of persons likely to transmit undesirable characteristics to their descendants. Objections to this measure have been raised on moral grounds and also because of its relatively low efficiency in reducing the frequency of recessive genes (912-6). Among the measures proposed, pre-marital examination⁵ may be mentioned; this is designed to give couples intending to marry information about the probable quality of their offspring, so that prospective partners to dysgenic marriages⁶, i.e., those likely to produce defectives, may be warned.

914

The probability that an individual of reproductive age will have a given number of offspring who also attain reproductive age may depend on his genotype (912-1). This differential reproduction is called selection¹. The selective value² or fitness value² of a genotype is the relative number of children of individuals with the genotype who survive to reproductive age. The mean selective value³ or fitness³ of a population is equal to the average of the selective values for the genotypes of its members. The genetic load⁴ of the population is the relative decline in the mean value of fitness resulting from the presence of different genotypes with varying fitness values. Random fluctuation of the frequency with which a specific gene is found in different generations of a population is called the genetic drift⁵. The gene structure⁶ of a population refers to the distribution of the frequencies of different alleles (911-5) on a given locus (911-4) within the members of the population. The genotypic structure⁷ of a population refers to the distribution of different genotypes on the same locus.

915

In the case of an inbred individual, i.e., an individual whose parents have a common ancestor, two genes are said to be identical genes¹ by descent, if both were carried by the same ancestor and are on the same locus. The probability that an individual chosen at random in a population carries two genes identical by descent is the coefficient of inbreeding² of the population. The coefficient of kinship³ of a population is the probability that two individuals chosen at random in that population carry genes identical by descent on the same locus.