{"id":526,"date":"2023-11-27T21:44:20","date_gmt":"2023-11-27T21:44:20","guid":{"rendered":"https:\/\/cellandcelldivision.com\/?p=526"},"modified":"2023-11-27T21:45:26","modified_gmt":"2023-11-27T21:45:26","slug":"page-84","status":"publish","type":"post","link":"https:\/\/cellandcelldivision.com\/?p=526","title":{"rendered":"Page 84"},"content":{"rendered":"\n

In some representatives of the Hymenoptera<\/em> genus (bees, wasps, and
ants) the male individuals are normally haploid, while the female ones \u2014
diploid. Sometimes the egg develops without any fertilization i.e.
parthenogenetically. All these and other deviations might be assumed
contradictory to the chromosome theory. They are possibly due to errors in
the process of meiosis or to genetic mechanisms remaining still unclear.
The emergence of new forms at the cell or organism level differing
from the ones existing in nature had made researchers think about their
genesis. One of the most accepted hypothesis at that time was that
genes can change, i.e. mutate thus generating new (mutant) genes. In
1908\u20141910 this hypothesis was subjected to a serious test in T.
Morgan\u2019s Laboratory together with his collaborators C. Bridges, H. Muller
and A. Stertevent. As an object of the study they have used Drosophila
melanogaster which has only four homologous chromosomes. The first
mutant observed by them was with white eyes spontaneously emerged
in the collection of normally displaying red eyes. The gene determining
the red colour of the eyes was called wild type <\/strong>since it exists in nature
and the newly appeared gene controlling the white colour \u2014 mutant<\/strong>.
The mutant with white eyes was used for a crosses that have
yielded unexpected results. It proved that the mutant gene was
transmitted in the offspring with the X-chromosome, i.e. linked to the
sexual chromosome. The genes located in one and the same
chromosome transmitted to the offspring with the chromosome itself
were called linked genes.<\/strong> So in Drosophila<\/em> there had been established
four groups of linked genes which correspond to the four different
chromosomes in its haploid chromosome set.
With the studies in that direction it became clear why in some cases an
independent distribution of the features, as established earlier by Mendel, is
not observed. It was found that the independent inheritance of the features
is due to the genes location on different chromosomes which in the process
of meiosis are distributed independently from one another, and when they
are linked and are on one and the same chromosome their distribution is
not independent.
Sometimes, however, two genes located on the same chromosome are
not distributed evenly in the process of meiosis. This has led researchers to
the thought of mechanisms, by the help of which an exchange of genes
between homologous chromosomes may be occurring. This process was
called crossing-over<\/strong>. The X-like figures thus formed were called chiasmata.<\/strong>
In 1909 the Belgian cytologist F. Janssens has made the suggestion that
chiasmata are related to the exchange of segments of the chromosomes. This
is presented in Figure 2\u201316. The results from the numerous studies in support
of the chromosome theory undoubtedly place the concept of the
chromosomes as bearers of heredity. Each cell both independently living or
included in the composition of a given organism has a specific genome with a<\/p>\n","protected":false},"excerpt":{"rendered":"

In some representatives of the Hymenoptera genus (bees, wasps, andants) the male individuals are normally haploid, while the female ones \u2014diploid. Sometimes the egg develops without any fertilization i.e.parthenogenetically. All these and other deviations might be assumedcontradictory to the chromosome theory. They are possibly due to errors inthe process of meiosis or to genetic mechanisms […]<\/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-526","post","type-post","status-publish","format-standard","hentry","category-book"],"_links":{"self":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/526","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=526"}],"version-history":[{"count":2,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/526\/revisions"}],"predecessor-version":[{"id":534,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/526\/revisions\/534"}],"wp:attachment":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=526"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=526"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=526"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}