204. Heredity

See also 15. ANCESTORS ; 44. BIOLOGY ; 147. EVOLUTION ; 307. PARENTS ; 341. RACE .

generation of living organisms from inanimate matter. Also called spontaneous generation .
the congenital absence of the brain and spinal cord in a devel-oping fetus.
the science or study of biotypes, or organisms sharing the same hereditary characteristics —biotypologic, biotypological , adj.
the theory that hereditary characteristics are transmitted by germ plasm. Cf. pangenesis . —blastogenetic , adj.
the entire substance of a cell excluding the nucleus.
deoxyribonucleic acid (DNA)
the complex substance that is the main carrier of genetic information for all organisms and a major component of chromosomes.
deoxyribonucleic acid.
lack of or partial fertility, as found in hybrids like the mule, which cannot breed amongst themselves but only with the parent stock. —dysgenetic , adj.
alternation of generations. —geneagenetic , adj.
1. Biology. the science of heredity, studying resemblances and differences in related organisms and the mechanisms which explain these phenomena.
2. the genetic properties and phenomena of an organism. —geneticist , n . — genetic , adj.
a believer in the theory that heredity, more than environment, determines nature, characteristics, etc.
the normal course of generation in which the offspring resembles the parent from generation to generation. —homogenetic , adj,
the laws of inheritance through genes, discovered by Gregor J. Mendel. —Mendelian . n ., adj.
the theory advanced by Darwin, now rejected, that transmission of traits is caused by every cell’s throwing off particles called gemmules, which are the basic units of hereditary transmission. The gemmules were said to have collected in the reproductive cells, thus ensuring that each cell is represented in the germ cells. Cf. blastogenesis . —pangenetic , adj.
Haeckel’s theory of generation and reproduction, which assumes that a dynamic growth force is passed on from one generation to the next. —perigenetic , adj.
the capacity of one parent to impose its hereditary characteristics on offspring by virtue of its possessing a larger number of homozygous, dominant genes than the other parent. —prepotent , adj.
a division of radiobiology that studies the effects of radioactiv-ity upon factors of inheritance in genetics. —radiogenic , adj.
recombinant DNA
a DNA molecule in which the genetic material has been artificially broken down so that genes from another organism can be intro-duced and the molecule then recombined, the result being alterations in the genetic characteristics of the original molecule.
ribonucleic acid (RNA)
a nucleic acid found in cells that transmits genetic instructions from the nucleus to the cytoplasm.
ribonucleic acid.
the supposed transmission of hereditary characteristics from one sire to offspring subsequently born to other sires by the same female. —telegonic , adj.
the theories of development and heredity asserted by August Weismann (1834-1914), esp. that inheritable characteristics are carried in the germ cells, and that acquired characteristics are not hereditary. —Weismannian , n., adj.
1. abiogenesis; spontaneous generation.
2. metagenesis, or alternation of generations.
3. production of an offspring entirely different from either of the parents. Also xenogeny . —xenogenic, xenogenetic , adj.

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