{"id":10651,"date":"2020-09-28T15:22:32","date_gmt":"2020-09-28T15:22:32","guid":{"rendered":"https:\/\/gkscientist.com\/?p=10651"},"modified":"2021-04-04T10:35:26","modified_gmt":"2021-04-04T10:35:26","slug":"mendelism-or-mendels-principles-of-inheritance","status":"publish","type":"post","link":"https:\/\/gkscientist.com\/mendelism-or-mendels-principles-of-inheritance\/","title":{"rendered":"Mendelism or Mendel&#8217;s Principles of Inheritance"},"content":{"rendered":"\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_65 counter-hierarchy ez-toc-counter ez-toc-light-blue ez-toc-container-direction\">\n<p class=\"ez-toc-title\">Table of Contents<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-662e4db9e8292\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-662e4db9e8292\"  aria-label=\"Toggle\" \/><nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/gkscientist.com\/mendelism-or-mendels-principles-of-inheritance\/#Mendelism\" title=\"Mendelism:\">Mendelism:<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/gkscientist.com\/mendelism-or-mendels-principles-of-inheritance\/#Monohybrid_Cross\" title=\"Monohybrid Cross:\">Monohybrid Cross:<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/gkscientist.com\/mendelism-or-mendels-principles-of-inheritance\/#Law_of_Dominance\" title=\"Law of Dominance:\">Law of Dominance:<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/gkscientist.com\/mendelism-or-mendels-principles-of-inheritance\/#Law_of_Segregation\" title=\"Law of Segregation:\">Law of Segregation:<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/gkscientist.com\/mendelism-or-mendels-principles-of-inheritance\/#Dihybrid_Cross_and_Law_of_Independent_Assortment\" title=\"Dihybrid Cross and Law of Independent Assortment:\">Dihybrid Cross and Law of Independent Assortment:<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/gkscientist.com\/mendelism-or-mendels-principles-of-inheritance\/#What_is_Punnett_Square\" title=\"What is Punnett Square?\">What is Punnett Square?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/gkscientist.com\/mendelism-or-mendels-principles-of-inheritance\/#Important_Terms\" title=\"Important Terms:\">Important Terms:<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/gkscientist.com\/mendelism-or-mendels-principles-of-inheritance\/#Biological_Significance_of_Mendels_Laws\" title=\"Biological Significance of Mendel&#8217;s Laws:\">Biological Significance of Mendel&#8217;s Laws:<\/a><\/li><\/ul><\/nav><\/div>\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Mendelism\"><\/span>Mendelism:<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p><strong>Gregor Johann Mendel<\/strong>, a monk carried his experiments by crossing varieties of garden peas and recording his results in a monastery garden of a town in Moravia, from<strong> 1857 <\/strong>to <strong>1865<\/strong>. In <strong>1866<\/strong> he published his important conclusions in regard to heredity in the Proceedings of the <strong>Natural History Society of Brunn<\/strong>. But unfortunately, the scientists did not pay much attention to his findings and thus his result remained unnoticed until <strong>1900<\/strong>. About the beginning of the <strong>20th century<\/strong>, <strong>16 years<\/strong> after Mendel&#8217;s death, his laws were rediscovered by three European scientists, <strong>Correns<\/strong>, <strong>Hugo de Vries<\/strong>, and <strong>von Tschermak<\/strong>. The rediscovery created a sensation all over the scientific world. Mendel&#8217;s theory brought a dramatic change in the thinking about man and heredity. His basic rules of heredity are applicable to all forms of life.<\/p>\n\n\n\n<p>Mendel is called the <strong>Father of Genetics<\/strong>.<\/p>\n\n\n\n<p>The basic principles of inheritance as formulated by Mendel are collectively called <strong>Mendel&#8217;s principles of inheritance<\/strong> or <strong>Mendelism<\/strong>.<\/p>\n\n\n\n<script async=\"\" src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js\"><\/script>\n<ins class=\"adsbygoogle\" style=\"display:block; text-align:center;\" data-ad-layout=\"in-article\" data-ad-format=\"fluid\" data-ad-client=\"ca-pub-6083838409460826\" data-ad-slot=\"5867268109\"><\/ins>\n<script>\n     (adsbygoogle = window.adsbygoogle || []).push({});\n<\/script>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Monohybrid_Cross\"><\/span>Monohybrid Cross:<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>Monohybrid Cross refers to <strong>hybridization<\/strong> where two forms of a single trait are brought together.<\/p>\n\n\n\n<p>Mendel carried the monohybrid cross on garden pea plants (<strong>Pisum sativum<\/strong>) by artificially transferring the pollen grains of one plant to the stigma of another plant. The individuals produced to such parents are called <strong>hybrids<\/strong>. The first generation of hybrids is called as first filial generation (<strong>F<sub>1<\/sub> generation<\/strong>).<\/p>\n\n\n\n<p>He crossed <strong>pure tall pea plant<\/strong> with a <strong>pure dwarf pea plant<\/strong> and obtained the <strong>F<sub>1<\/sub> generation<\/strong> with all tall plants. He noticed that in the F1 generation, only one of the contrasting characters (<strong>tallness<\/strong>) appears and the other remained hidden (<strong>dwarf<\/strong>). The character that appears in <strong>F<sub>1<\/sub><\/strong> <strong>individuals<\/strong> is called a <strong>dominant character<\/strong> and the character that is not expressed in <strong>F<sub>1<\/sub> individuals<\/strong> is known as <strong>recessive<\/strong>.<\/p>\n\n\n\n<p>Then, he intercrossed the <strong>F<sub>1<\/sub><\/strong> hybrids and obtained the hybrids of the second filial generation (<strong>F<\/strong><sub><strong>2<\/strong><\/sub>). In the <strong><strong>F<\/strong><sub><strong>2<\/strong><\/sub><\/strong> generation, the tall and dwarf were obtained in the ratio of <strong>3 : 1<\/strong> (<strong>phenotypic ratio<\/strong>) but genetically, this ratio was recognized in three groups of plants viz. <strong>TT<\/strong>, <strong>Tt<\/strong>, and <strong>tt<\/strong> with ratio <strong>1 : 2 : 1<\/strong> (<strong>genotypical ratio<\/strong>).<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"381\" height=\"686\" src=\"https:\/\/i0.wp.com\/gkscientist.com\/wp-content\/uploads\/2020\/09\/monohybrid-cross.jpg?resize=381%2C686&#038;ssl=1\" alt=\"monohybrid cross\" class=\"wp-image-10691\" title=\"\" srcset=\"https:\/\/i0.wp.com\/gkscientist.com\/wp-content\/uploads\/2020\/09\/monohybrid-cross.jpg?w=381&amp;ssl=1 381w, https:\/\/i0.wp.com\/gkscientist.com\/wp-content\/uploads\/2020\/09\/monohybrid-cross.jpg?resize=167%2C300&amp;ssl=1 167w\" sizes=\"(max-width: 381px) 100vw, 381px\" data-recalc-dims=\"1\" \/><\/figure><\/div>\n\n\n\n<p><strong>He came to two important conclusions from these experimental results<\/strong>&#8211;<\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Law_of_Dominance\"><\/span>Law of Dominance:<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>When a cross is made between two <strong>homozygous<\/strong> (pure) individuals, only one of the two characters of the pair appears in the <strong>F<sub>1<\/sub> generation<\/strong>. There is an appearance of both the characters in the <strong>F<sub>2<\/sub> generation<\/strong>.<\/p>\n\n\n\n<p class=\"has-text-align-center\"><strong>Or<\/strong><\/p>\n\n\n\n<p>The characters are controlled by discrete units called <strong>factors<\/strong> and these occur in pairs. In a dissimilar pair of factors, one member of the pair dominates (<strong>dominant<\/strong>) and the other (<strong>recessive<\/strong>).<\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Law_of_Segregation\"><\/span>Law of Segregation:<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>The two <strong>allelomorphic<\/strong> characters of an individual do not get mixed up but they segregate during gametic formation. Each gamete receives only one character of the two allelomorphs and a paired condition is restored by random fusion of gametes during fertilization. It is also called the <strong>Law of Purity of Gametes<\/strong>.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Dihybrid_Cross_and_Law_of_Independent_Assortment\"><\/span>Dihybrid Cross and Law of Independent Assortment:<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>The inheritance of two or more genes at a time, their distribution in the gametes, and in the progeny of subsequent generation is independent of each other. <\/p>\n\n\n\n<p>The law can be deduced from a dihybrid cross. A cross is made between a pure <strong>round yellow seeded <\/strong>Pea plant (<strong>RR YY<\/strong>) with a <strong>wrinkled green seeded <\/strong>Pea plant (<strong>rr yy<\/strong>). The yellow colour is dominant over the green and the rounded seed shape over the wrinkled seed shape. <strong>F<sub>1 <\/sub>plants<\/strong> or hybrid plants are all round and yellow seeded. <strong>F<sub>1 <\/sub>plants<\/strong> are allowed to self breed and produce the F2 generation. F2 generation has four types of plants- round yellow, wrinkled yellow, round green, and wrinkled green in the ratio of 9 : 3 : 3 : 1. Each of the character if considered separately shows a ratio of <strong>3:1<\/strong> as found in the monohybrid cross.<\/p>\n\n\n\n<p><strong>Seed Colour:<\/strong><\/p>\n\n\n\n<p>Yellow 9 + 3 = 12<\/p>\n\n\n\n<p>Green 3 + 1 = 4<\/p>\n\n\n\n<p>Ratio between yellow and green = 12 : 4 or 3 : 1<\/p>\n\n\n\n<p><strong>Seed Texture:<\/strong><\/p>\n\n\n\n<p>Round 9 + 3 = 12<\/p>\n\n\n\n<p>Wrinkled 3 + 1 = 4<\/p>\n\n\n\n<p>Ratio between round and wrinkled = 12 : 4 or 3 : 1<\/p>\n\n\n\n<p>The <strong>F<sub>2 <\/sub><\/strong>ratio of <strong>9 : 3 : 3 : 1<\/strong> further shows two types of recombinants, wrinkled yellow and rounded green. They can be produced only if the alleles of the two different characters are free to recombine, i.e., assort and combine independent of each other. The same can be confirmed with the help of <strong>Punnett square<\/strong> or <strong>checkerboard<\/strong>.<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"473\" height=\"612\" src=\"https:\/\/i0.wp.com\/gkscientist.com\/wp-content\/uploads\/2020\/09\/dihybrid-cross.jpg?resize=473%2C612&#038;ssl=1\" alt=\"dihybrid cross\" class=\"wp-image-10715\" title=\"\" srcset=\"https:\/\/i0.wp.com\/gkscientist.com\/wp-content\/uploads\/2020\/09\/dihybrid-cross.jpg?w=473&amp;ssl=1 473w, https:\/\/i0.wp.com\/gkscientist.com\/wp-content\/uploads\/2020\/09\/dihybrid-cross.jpg?resize=232%2C300&amp;ssl=1 232w\" sizes=\"(max-width: 473px) 100vw, 473px\" data-recalc-dims=\"1\" \/><\/figure><\/div>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"What_is_Punnett_Square\"><\/span>What is Punnett Square?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>It is a graphical representation to calculate the probability of all possible genotypes of offsprings in a genetic cross.<\/p>\n\n\n\n<p>All possible gametes are written on the top row and left columns. All possible combinations are represented in boxes, which generates a square output form.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Important_Terms\"><\/span>Important Terms:<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul><li><strong>Hybrids:<\/strong> The offsprings produced after a cross between two opposite sexes of two different species or genera are called hybrids.<\/li><\/ul>\n\n\n\n<ul><li><strong>Hybridization<\/strong>: The crossing of two individuals of the same species or genus is called hybridization.<\/li><\/ul>\n\n\n\n<ul><li><strong>Homozygous and heterozygous:<\/strong> <strong>Bateson and Saunders <\/strong>(<strong>1902<\/strong>) coined the term homozygous and heterozygous. The diploid individuals possessing sets of similar traits or characters (<strong>TT or tt<\/strong>) are called homozygous. On the other hand zygote or diploid individuals carrying both the factors of a pair of alleles is called heterozygous or heterozygote. Heterozygote (<strong>Tt<\/strong>) arises when two individuals with different genetic traits are crossed.<\/li><\/ul>\n\n\n\n<ul><li><strong>Phenotype:<\/strong> <strong>Johanson<\/strong> (<strong>1909<\/strong>) coined the term to represent visible external characters of an organism.<\/li><\/ul>\n\n\n\n<ul><li><strong>Genotype: <\/strong>The genetic constituents of an individual is called genotype.<\/li><\/ul>\n\n\n\n<ul><li><strong>Monohybrid cross:<\/strong> The cross between two parents having only one pair of contrast characters is called monohybrid cross.<\/li><\/ul>\n\n\n\n<ul><li><strong>Dihybrid cross:<\/strong> The cross between two parents having two pairs of contrast characters is called dihybrid cross.<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Biological_Significance_of_Mendels_Laws\"><\/span>Biological Significance of Mendel&#8217;s Laws:<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>Mendel&#8217;s laws offer several advantages in producing hybrids of plants and animals of desired traits that normally do not exist in nature. Even in a single variety, the desired characters can be combined and maintained. Many disease resistant and high yielding varieties of crop and ornamental plants are being produced. Bases of success of all these varieties lie on Mendel&#8217;s laws. These laws form a base for predicting the outcome of crosses in eukaryotic organisms.<\/p>\n\n\n\n<figure class=\"wp-block-embed aligncenter is-type-wp-embed is-provider-gk-scientist wp-block-embed-gk-scientist\"><div class=\"wp-block-embed__wrapper\">\n<blockquote class=\"wp-embedded-content\" data-secret=\"JLViebPhWi\"><a href=\"https:\/\/gkscientist.com\/dna-fingerprinting-process-and-application\/\">DNA Typing or DNA Profiling or DNA Fingerprinting<\/a><\/blockquote><iframe class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; clip: rect(1px, 1px, 1px, 1px);\" title=\"&#8220;DNA Typing or DNA Profiling or DNA Fingerprinting&#8221; &#8212; GK SCIENTIST\" src=\"https:\/\/gkscientist.com\/dna-fingerprinting-process-and-application\/embed\/#?secret=YZ5vRu6EWS#?secret=JLViebPhWi\" data-secret=\"JLViebPhWi\" width=\"600\" height=\"338\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe>\n<\/div><\/figure>\n\n\n\n<ul><li><a rel=\"noreferrer noopener\" href=\"https:\/\/gkscientist.com\/human-genome-project\/\" target=\"_blank\">Human Genome Project<\/a><\/li><li><a rel=\"noreferrer noopener\" href=\"https:\/\/gkscientist.com\/homologous-analogous-and-vestigial-organs\/\" target=\"_blank\">Homologous Analogous And Vestigial Organs<\/a><\/li><li><a rel=\"noreferrer noopener\" href=\"https:\/\/gkscientist.com\/lamarckism-and-neo-lamarckism-for-cbse-exam\/\" target=\"_blank\">Lamarckism And Neo-Lamarckism<\/a><\/li><li><a href=\"https:\/\/gkscientist.com\/darwinism-or-theory-of-natural-selection\/\">Darwinism or Theory of Natural Selection<\/a><\/li><li><a aria-label=\"Genetic Drift (opens in a new tab)\" href=\"https:\/\/gkscientist.com\/genetic-drift-and-its-influence-on-evolution\/\" target=\"_blank\" rel=\"noreferrer noopener\" class=\"rank-math-link\">Genetic Drift<\/a><\/li><li><a rel=\"noreferrer noopener\" href=\"https:\/\/drive.google.com\/file\/d\/1wy3C7vK64r7lMUVNk-pfJEhOgK0QtROj\/view?usp=sharing\" target=\"_blank\">Origin and Evolution of Life<\/a><\/li><\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Mendelism: Gregor Johann Mendel, a monk carried his experiments by crossing varieties of garden peas and recording his results in a monastery garden of a town in Moravia, from 1857 to 1865. In 1866 he published his important conclusions in regard to heredity in the Proceedings of the Natural History Society of Brunn. But unfortunately, the scientists did not pay much attention to his findings and thus his result remained unnoticed until 1900. About the beginning of the 20th century, 16 years after Mendel&#8217;s death, his laws were rediscovered by three European scientists, Correns, Hugo de Vries, and von Tschermak. <\/p>\n","protected":false},"author":1,"featured_media":10724,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[7],"tags":[488,487,486,485,484],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/i0.wp.com\/gkscientist.com\/wp-content\/uploads\/2020\/09\/Mendels-Principles-of-Inheritance.jpg?fit=350%2C270&ssl=1","_links":{"self":[{"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/posts\/10651"}],"collection":[{"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/comments?post=10651"}],"version-history":[{"count":0,"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/posts\/10651\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/media\/10724"}],"wp:attachment":[{"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/media?parent=10651"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/categories?post=10651"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gkscientist.com\/wp-json\/wp\/v2\/tags?post=10651"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}