It is very difficult practically (and may be unnecessary) to survey and
discuss the results from the numerous studies on the transfer of genetic
material from the donor cell into the recipient cell, the various
recombinations resulting from that act and the mechanisms controlling it,
the exchange and binding of the genetic markers, competence or
incompetence of the recipient cells, phage conversion, the kinetics of these
processes, etc. All these problems are considered in detail in the
specialized literature. It is however necessary to note that the discovery of
transformation, conjugation and transduction has served as a solid proof for
the assumption that hereditary information is confined to the DNA molecule.
This has played an essential role in the building of the chromosome theory.
In the period 1944\u20141950 comparative measurements of the DNA
content in the nuclei of cells from different organisms were made. The data
have shown that the quantity of DNA in a complete chromosome set
remains unaltered for all cells of the given organisms while the protein
content is subject to significant changes. On the basis of these results
some authors (Boivin et al., 1948; Vendrely, Vendrely, 1948, 1949; Swift,
1950 a, b, etc.) have forwarded the hypothesis for the permanent amount of
DNA which in polyploid cells is increased multiply to ploidity (2n, 3n, 4n,
etc.) and in sexual cells is reduced to half the diploid chromosome number.
At present, data is available about the intraspecific differences in the DNA
content which are not to be discussed.
At the same time the American biochemist E. Chargaff (1950) has
established that the sum of the purine bases (adenine, guanine) is equal to
the pyrimidine bases (thymine, cytosine). Besides he has discovered that
the quantity of thymine (T) is equal to that of adenine (A) and the one of
guanine (G) is equal to that of cytosine (C), and these ratios varying in the
different types of organisms. This fact has served as a ground for the
assumption that the differences among DNA molecules are greater than it
has been admitted in the already mentioned hypothesis for the
tetranucleotide structure of nucleic acids. These data known as the
Chargaff\u2019s rules have been implemented in the disclosure of the spatial
structure of DNA.
In 1953 Watson and Crick (Watson, Crick 1953 a, b) have published
their model of the DNA double helix and thus have shown the possibilities for
its self-replication which has marked the onset of modern molecular biology
and genetics. This problem will be considered in more detail in Section 2. 7
(Nucleic acids).<\/p>\n","protected":false},"excerpt":{"rendered":"
It is very difficult practically (and may be unnecessary) to survey anddiscuss the results from the numerous studies on the transfer of geneticmaterial from the donor cell into the recipient cell, the variousrecombinations resulting from that act and the mechanisms controlling it,the exchange and binding of the genetic markers, competence orincompetence of the recipient cells, […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[6],"tags":[],"class_list":["post-500","post","type-post","status-publish","format-standard","hentry","category-book"],"_links":{"self":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/500","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=500"}],"version-history":[{"count":1,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/500\/revisions"}],"predecessor-version":[{"id":518,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/500\/revisions\/518"}],"wp:attachment":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=500"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=500"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=500"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}