biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7-7-2g2n8ssqnyw

<h3 id="successmultiple-allelismsuccess"><Success>Multiple allelism</Success></h3>
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<ul>
<li>
<p>Occurrence of many alleles for a particular gene, controlling a particular character seen in different individuals of a population</p>
</li>
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<p>Each allele may produce a different phenotype</p>
</li>
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<p>Multiple alleles occur in the same locus of a homologous chromosome</p>
</li>
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<p>They are the mutant forms of the same gene</p>
</li>
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<p>They affect a same trait</p>
</li>
<li>
<p>E.g. ABO blood group system</p>
</li>
</ul>








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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-015-0060.0.jpg"></p>

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<h3 id="successabo-blood-systemsuccess"><Success>ABO blood system</Success></h3>
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<ul>
<li>
<p>ABO Blood system was discovered by Landsteiner</p>
</li>
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<p>AB blood group was discovered de Castello and Steini in 1902</p>
</li>
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<p>Blood grouping is based on antigens present on the surface of RBC</p>
</li>
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<p>Antibody is present in the serum</p>
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<p>There are four types of blood groups, such as A, B, AB and O</p>
</li>
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<p>They are produced by different three different alleles. represented by |A |B |O</p>
</li>
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<p>I stands for immunoglobulin</p>
</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-017-0222.0.jpg"></p>
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<p>======</p>
<h3 id="successabo-blood-systemsuccess-1"><Success>ABO blood system</Success></h3>
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<ul>
<li>
<p>I<sup>A</sup> allele is dominant over I<sup>o</sup> allele</p>
</li>
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<p>I<sup>B</sup> allele is dominant over I<sup>o</sup> allele</p>
</li>
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<p>I<sup>A</sup> and I<sup>B</sup> alleles are co-dominant</p>
</li>
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<p>I<sup>o</sup> allele is recessive</p>
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<p>In ABO blood group system, there are 4 different phenotypes and 6 different genotypes</p>
</li>
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<p>A blood group is produced by I<sup>A</sup> allele</p>
</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-01.jpg"></p>
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<h3 id="successabo-blood-systemsuccess-2"><Success>ABO blood system</Success></h3>
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<ul>
<li>
<p>B blood group is produced by I<sup>B</sup> allele</p>
</li>
<li>
<p>O blood group is produced by I<sup>O</sup> allele</p>
</li>
<li>
<p>AB blood group is produced by I<sup>A</sup> and I<sup>B</sup> alleles</p>
</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-018-0478.8.jpg"></p>
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<p>======</p>
<h3 id="successmultiple-allelismsuccess-1"><Success>Multiple allelism</Success></h3>
<div style='float: left; width:50%;font-size:30px;text-align:left;'>
<ul>
<li>
<p>Definition: more than two alleles</p>
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<p>(more than 2 alleles exist in a population not an individual)</p>
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</ul>
<p>Example: rabbit’s coat color</p>
<p>Example: human’s blood type</p>
<p><strong>blood-type donors and recipients</strong></p>
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<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/993366c8-acf4-439b-1675-96ab9f12a700/public" width="70%" >

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<h3 id="successchromosome-theory-of-hereditysuccess"><Success>Chromosome theory of heredity</Success></h3>
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<ul>
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<p>Put forward by Sutton and Boveri</p>
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<p>According to them the pairing and segregation of a pair of chromosomes would lead to the segregation of a pair of factors they carried</p>
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<p>Sutton united chromosomal segregation with Mendelian principles</p>
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<p>This theory states that chromosomes are the vehicles of inheritance as they carry the hereditary factors or genes and these hereditary factors are transferred parents to offsprings through successive generations</p>
</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-04.jpg"></p>
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<h3 id="successparallelism-between-the-genes-and-chromosomessuccess"><Success>Parallelism between the genes and chromosomes</Success></h3>
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<ul>
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<p>Both genes and chromosomes are seen as pairs and each member of the pair is contributed by different parents</p>
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<p>Genes remain unaltered in the subsequent generations</p>
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<p>Both will segregate at the time of gamete formation and only one of each pair will move to one gamete</p>
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<p>Segregation of one pair is independent from the segregation of the other pairs</p>
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<p>Paired condition is regained by fertilisation</p>
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</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-06.jpg"></p>
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<h3 id="successlinkage-and-crossing-oversuccess"><Success>Linkage and crossing over</Success></h3>
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<ul>
<li>
<p>The tendency of the genes present in the same chromosome to remain together and travel together from generation to generation is called linkage</p>
</li>
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<p>The genes located in the same chromosome are called linked genes</p>
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<p>Example-  The gene controlling red eye colour and grey body in Drosophila lie in the same chromosome, and are transmitted together to the next generation</p>
</li>
</ul>





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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-028-1344.0.jpg"></p>

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<p>======</p>
<h3 id="successgene-linkage-and-polyploidysuccess"><Success>Gene linkage and polyploidy</Success></h3>
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<ul>
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<p>There are several genes on a chromosome</p>
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<p>Gene Linkage-</p>
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<p>When two genes are close to each other on the same chromosome</p>
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</ul>
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<p><img alt="alt text" src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/ff4b6279-cd95-4c7b-ffb9-6f20b04e2500/public"></p>
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<h3 id="successunlinked-genessuccess"><Success>Unlinked genes</Success></h3>
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<p>Unlinked genes located on different chromosomes assort differently and give a dihybrid ratio of 9:3:3:1.</p>
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<p>It shows a test cross ratio 1:1:1:1</p>
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<p>Linked genes located in the same chromosome usually do not assort independently</p>
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<p>They give a dihybrid ratio 3:1 and a test</p>
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</ul>







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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-029-1720.8.jpg"></p>

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<p>======</p>
<h3 id="successexample-of-complete-linkagesuccess"><Success>Example of complete linkage</Success></h3>
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<ul>
<li>
<p>In Drosophila, a homozygous red eyed and normal winged (wild type) female is crossed with double recessive male</p>
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<p>F1 flies are all heterozygous red eyed and normal winged</p>
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<p>The F1 dihybrid female fly is then test crossed with recessive male with white and vestigial wings, the progenies comprises only two types of flies - red eyed normal winged, and white vestigial winged in the ratio - 1: 1</p>
</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-08.jpg"></p>
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<h3 id="successexample-of-complete-linkagesuccess-1"><Success>Example of complete linkage</Success></h3>
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<ul>
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<p>No recombinants are formed</p>
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<p>It is because there is no crossing over between the linked genes</p>
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<p>Morgan crossed a white eyed and miniature winged female drosophila with red eyed and normal winged male</p>
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<p>In the F1. one red eyed and normal winged female is produced, and one white eyed miniature male is produced</p>
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<p>When the F1 females are inter crossed, in the F2 generation, three red eyed and normal winged progenies and one white eyed and miniature winged</p>
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<p>progenies are produced(3:1)</p>
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</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-033-2007.6.jpg"></p>
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<p>======</p>
<h3 id="successlinkage-groupsuccess"><Success>Linkage group</Success></h3>
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<ul>
<li>
<p>All the genes in a particular chromosome forma linkage group</p>
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<p>Since the genes in a particular chromosome, have its alleles in the homologous chromosome, a pair of homologous   chromosomes are considered as a single linkage group</p>
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<p>So, human beings have 23 linkage groups</p>
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<p>Drosophila has 4 linkage groups</p>
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<p>Maize have 10 linkage groups</p>
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<p>Garden pea has 7 linkage group</p>
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</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-09.jpg"></p>
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<h3 id="successlinkagesuccess"><Success>Linkage</Success></h3>
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<ul>
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<p>Traits in Morgan’s cross are-</p>
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<p>The yellow body allele (y) is recessive to the gray body allele (y+)</p>
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<p>The white eyed allele (w) is recessive to the red eyed allele (w+)</p>
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<p>The miniature wing allele (m) is recessive to the normal winged allele (m+)</p>
</li>
</ul>





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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-034-2170.8.jpg"></p>

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<p>======</p>
<h3 id="successmorgans-experiment-with-drosophilasuccess"><Success>Morgan’s experiment with Drosophila</Success></h3>
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<ul>
<li>
<p>White eye colour gene (w) (recessive) and a gene for miniature wings (m) (recessive) are located on the X chromosome</p>
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<p>Morgan (1911) crossed a female white miniature (w m / wm) with a wild-type male (WM/WM)</p>
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</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-10.jpg"></p>
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<h3 id="successmorgans-experiment-with-drosophilasuccess-3"><Success>Morgan’s experiment with Drosophila</Success></h3>
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<ul>
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<p>In F2. the most frequent phenotypes for both sexes were the phenotypes of the parents in the original cross</p>
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<p>white eyes with miniature wings, and red eyes with normal wings</p>
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<p>Non-parental phenotypes (white eyes with normal wings or red eyes and miniature wings)</p>
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<p>Well below the 50% predicted for independent assortment</p>
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<p>During meiosis alleles of some genes assort together because they are near each other on the same chromosome</p>
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<p>Recombination occurs when genes are exchanged between X chromosomes of the F1 females</p>
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</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-042-2563.2.jpg">
<img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-18.jpg"></p>
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<p>======</p>
<h3 id="successlinkage-in-sweet-peasuccess"><Success>Linkage in sweet pea</Success></h3>
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<ul>
<li>
<p>Bateson and Punnet, studied in 1905 traits of sweet peas such as</p>
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<p>Flower colour can be either purple or red</p>
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<p>Purple is dominant to red</p>
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<p>Pollen shape can be either oblong or round</p>
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<p>Oblong is dominant to round</p>
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</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-19.jpg"></p>
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<p>======</p>
<h3 id="successlinkage-in-sweet-peasuccess-1"><Success>Linkage in sweet pea</Success></h3>
<div style='float: left; width:100%;font-size:30px;text-align:left;'>
<ul>
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<p>Bateson crossed Purple, long (PPLL) x red, round (ppll) plants</p>
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<p>F1 offspring are purple, long (PpLI)</p>
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<p>F 2 - crossing PpLI × PpLI</p>
</li>
</ul>
<p>gametes are - PL, PI, PL, pl)</p>
<ul>
<li>
<p>F2 possess four different phenotypes</p>
</li>
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<p>In F2 generation the observed ratio is 15.6 : 1.0: 1.4:4.5</p>
</li>
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<p>The expected ratio 9:3:3:1</p>
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<p>It is not seen</p>
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</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-20.jpg"></p>
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<h3 id="successdifferences-between-monogenic-inheritance-and-polygenic-inheritancesuccess"><Success>Differences between monogenic inheritance and Polygenic Inheritance</Success></h3>
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<p><strong>Monogenic inheritance</strong></p>
<ul>
<li>
<p>Deals with qualitative traits</p>
</li>
<li>
<p>Controlled by single pair of contrasting genes</p>
</li>
<li>
<p>Phenotype shows discontinuous variation</p>
</li>
<li>
<p>No intermediate phenotypes are produced</p>
</li>
</ul>
</div>
<div style='float: right; width:50%;font-size:30px'>
<p><strong>Polygenic inheritance</strong></p>
<ul>
<li>
<p>Deals with quantitative traits</p>
</li>
<li>
<p>Controlled by more than one pair of non-allelic genes</p>
</li>
<li>
<p>Phenotype shows continuous variation</p>
</li>
<li>
<p>Intermediate phenotypes are produced</p>
</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-051-3278.4.jpg"></p>
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<h3 id="successthalassemiasuccess"><Success>Thalassemia</Success></h3>
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<ul>
<li>Antasomal recessive disorder
Cause -  mutation / Deletion<br>
Effect - reduced rate of synthesis of globin chain $\rarr$ Abnormal haemoglobin</li>
</ul>
<p>Types - $\alpha$, $\beta$ Thalassemia</p>
<p>$\alpha$ Thalassemia - HbA,, Hb A<sub>2</sub> genes (- 16 chromosom) $\rarr$ Deletion/mutatio</p>
<p>$\beta$ -Thalassemia HBB gone (chromosome 11) $\rarr$ mutation</p>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-06-chapter-07-genetics-evolution-principles-of-inheritance-variation-l-7_7-2g2n8ssqnyw-17.jpg"></p>
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