mendelian genetics

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men·de·li·an ge·net·ics

the study of the pattern of segregation of phenotypes under the control of genetic loci taken one at a time.
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Mendelian genetics


Mendel's laws

the basic laws of inheritance, first published by Gregor MENDEL in 1866 to explain the results he obtained from experiments with the garden pea. Working without detailed knowledge of cell structure or nuclear division he suggested that:
  1. each character (e.g. height) is controlled by two factors. We would now state this idea as each gene having two alleles, one on each HOMOLOGOUS CHROMOSOME.
  2. each factor segregates in the egg and pollen grains. We would now state that MEIOSIS separates allelic forms of gene (Mendel's first law - see SEGREGATION).
  3. factors for different characters show INDEPENDENT ASSORTMENT. We would now state that genes are assorted independently during meiosis (Mendel's second law), unless linked on the same chromosome.
  4. factors do not cause blending, but are either dominant (see DOMINANCE (1) or recessive. We know now that we can explain dominance in terms of enzyme activity, and that sometimes two alleles code for enzymes giving an intermediate phenotype when together (see INCOMPLETE DOMINANCE).
  5. the distribution of factors in the egg cells and pollen grains obey basic statistical laws giving ratios in the progeny which are predictable.
  6. results from crosses are the same whether the dominant form of the character belongs to the female parent or the male parent. We now know that this statement is true only if the gene is located on an AUTOSOME (see SEX LINKAGE).
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
Majeed syndrome is an autosomal recessive syndrome, and according to Mendelian genetics, Majeed syndrome symptoms should not be expressed.
This included a review of the concepts of variation, adaptation and fitness as used in evolution, structure and function of DNA, Mendelian genetics and the role that variation plays in natural selection, biogeography, geological time and extinction.
He also taught a graduate course on Mendelian genetics, many guest lectures, as well as short courses in the USA and abroad.
Historically, the ideas of Lamarck (1744-1829), that evolution occurs when parent organisms pass on to their offspring characteristics they have acquired during their lifetimes began to be ridiculed after they were superseded by Darwinism and Mendelian genetics. However, it was only in the late 1940s that Salvatore Luria finally proclaimed the "fall of the last bastion of Lamarckism" soon after Joshua Lederberg discovered that bacteria practice sexual recombination.
In 1911, barely 10 years after the principles of what we now term Mendelian genetics became generally recognized, Wilhelm Johannsen, a Danish botanist, introduced the term "gene".
Before the emergence of modern Mendelian genetics, the environmental and breeding components of eugenics were not clearly distinguishable.
Indeed, Mendelian genetics as a science may be said to date from the dawn of the twentieth century, nearly two decades after Mendel's death in 1884.
So at the turn of the 20th century, scientists with a can-do spirit and just enough knowledge of Mendelian genetics to be dangerous devised grand schemes to improve the American "protoplasm": They would segregate, sterilize, and perhaps even murder those deemed "unfit"--as much as 10 percent of the population.
Mendelian genetics refers to the simple quantitative inheritance of genes that express themselves in defined and predictable phenotypes.
Mendelian genetics still provides a sufficient explanation for many inherited diseases.
From Newtonian physics and Mendelian genetics to cutting-edge chaos theories, science explains how and why the world--including the business world--works the way it does.