Fungal genetics / J.R.S. Finchman, P.R. Day.

  • Fincham, J. R. S.
Date:
1971
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Fungal genetics / J.R.S. Finchman, P.R. Day. Source: Wellcome Collection.

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    18 FUNGAL GENETICS their frequency and position from one cell to another; they occur after the paired chromosomes at the first division of meiosis have divided into chroma¬ tids, and they each involve only one chromatid from each chromosome, though different chromatids may participate in successive exchanges. Through the analysis of patterns of crossing-over, it is possible to construct linkage maps in which the loci of genetic differences are arranged in linear order, each corresponding to a particular site on a chromosome. If a change at a particular chromosomal locus can determine an inherited difference in the organism, there must clearly be physiologically important structures in the chromosome which can undergo change (mutation). Such structures, which are really only recognizable through their capacity for mutation, may conveniently be called genes. The more precise definition of the gene is quite a complicated matter, and will be discussed at much greater length in later chapters. For the present it will suffice to point out that alleles (mutually exclusive genetic factors located in corresponding segments of homologous chromosomes) may conveniently be defined as different forms of the same gene, and that many more than two alleles of one gene can exist, although, of course, no more than two of them can be present in any one diploid cell.