Bioengineering English
law: the law of segregation.This law states that for a given trait an organism inherits one allele from each parent. Together these alleles form the allele pair. When gametes are formed during meiosis, the two alleles become separated (halving of chromosome number).To gain evidence for his theory Mendel performed test crosses, mating plants of unknown genotype to plants that were homozygous recessive for the trait of interest. The ratio of dominant phenotypes (if any) in the progeny makes clear whether the unknown genotype is heterozygous, homozygous dominant, or homozygous recessive.
分离定律，生物只遗传父母本等位基因对的一个等位基因。减数分裂期形成配子时两个等位基因分离。为验证此理论，他做了测交实验，即基因型未知的植物与纯合的隐性基因植物杂交。子代显性表型可以明确测得杂合基因或纯合基因的基因型。 Mendel's Ideas and the Law of independent Assortment
Mendel also performed dihybrid crosses, which enabled him to consider how two traits are inherited relative to one another. This work let to the law of independent assortment, which states that the alleles of genes governing different characters are inherited independently. An apparent exception to Mendel's laws is incomplete dominance, a phenomenon in which offspring of a cross exhibit a phenotype that is intermediate between those of the parents. However, incomplete dominance reflects the fact that both alleles for the trait in question exert an effect on the phenotype. The alleles themselves remain separate.
双因子杂合试验，两个特征是如何相互影响遗传的。试验结果产生独自分配定律，即等位基因独立遗传。特例是，不完全显性。子代的表型是父母本的中间类型。不完全显性说明了两个等位基因对表型都有影响。，等位基因会继续分离。
Mendel presented his ideas in 1866 in a scientific paper published by the Brunn Society for Natural History. Unfortunately, the meaning of his research was not understood by other scientists of the day. His work was rediscovered in 1900 by Carl Correns and Hugo de Vries. 1866年，孟德尔在自然史上发表了他的科学论文，陈诉了他的观点。不幸的是，他的研
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Bioengineering English
究不被当时科学家接受。在1900年，他的著作再被发现利用。 Chromosomes and Mendelian Genetics
Soon after Mendel's work was rediscovered, Walter Sutton and Theodor Boveri independently proposed that the hereditary units might be located on chromosomes. Experiments to prove this hypothesis were carried out by Thomas Hunt Morgan and his students at Columbia University, in research on the sex chromosomes of fruit flies. Morgan's studies were also the first exploration of sex-linked traits. It also led to the discovery in 1916 by Calvin Bridges of the phenomenon of nondisjunction, in which a chromosome pair fails to segregate during meiosis.
孟德尔著作被再发现不久，Walter Sutton 和Theodor Boveri提出，遗传单位可能定位在染色体组上。伴性遗传又导致了不分离现象的发现，即在减数分裂中，染色体对不分离。
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Bioengineering English
Glossary
pangenesis 泛生论，泛生说
The theory of heredity postulating that germs, humours, or essences migrate from individual body cells to the sex organs and contribute to the gametes. germ plasm theory 种质学说
A substance thought to be transmitted in the gametes (germ cells) in an unchanged form from generation to generation. The germ plasm was believed to be unaffected by the environment and to give rise to the body cells. dominant 显性
The member of a pair of alleles that shows its effect in the phenotype whatever other allele is present. recessive 隐形的
The member of a pair of alleles that does not show its effect in the presence of any other allelic partner. allele 等位基因
Alternative forms of a gene for a particular characteristic (e.g., attached earlobe genes
and free earlobe genes are alternative alleles for ear shape). gene 基因
A unit of heredity located on a chromosome and composed a sequence of DNA nucleotides. homozygous 纯合的
A diploid organism that has two identical alleles for particular characteristic. heterozygous 杂合的
A diploid organism that has two different alletic forms of a particular gene. Genotype 基因型
The catalog of genes of an organism, whether or not these genes are expressed. phenotype 表型
The physical, chemical, and psychological expression of genes possessed by an organism. Punnett square 旁纳特方格
A method used to determine the probabilities of combination in a zygote. law of segregation 分裂定律
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Bioengineering English
When gametes are formed by a diploid organism, the alleles that control a trait separate from one another into different gametes, retaining their individuality. test cross 测交
A cross between a heterozygote of unknown genotype and an individual homozygous for the recessive genes in question
.dihybrid cross 双因子杂种，双因子杂合子 A cross between individuals that differ with respect to two specified gene pairs. law of independent assortment 独立分配定律，自由组合定律
Members of one gene pair will separate
from each other independently of the members of other gene pairs.
incomplete dominance 不完全显性 The condition in which two allelic genes have a different effect when they are together as a heterozygote in a diploid cell than either of them have in the homozygous state nondisjunction 不分离
The failure of separation of paired chromosomes at metaphase, resulting in one daughter receiving both and the other daughter cell none of the chromosomes in question. Nondisjunction can occur during a meiotic or mitotic division.
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