biology-class-12-unit-06-chapter-06-genetics-evolution-principles-of-inheritance-variation-l-6-7-23inkiossh8

<h3 id="successcolour-blindness-in-mansuccess"><Success>Colour blindness in man</Success></h3>
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<ul>
<li>
<p>Red green colour blindness is an example of sex linked inheritance. It is due to a recessive mutation of a normal dominant gene for colour vision</p>
</li>
<li>
<p>Inability to distinguish red from green colour due to lack of one of the primary con pigment in the retina</p>
</li>
<li>
<p>Males are usually more affected due to hemizygous
condition</p>
</li>
<li>
<p>It is due a recessive gene linked to the X chromosome</p>
</li>
<li>
<p>Females are affected only when both the X chromosomes have the recessive mutant allele</p>
</li>
<li>
<p>Heterozygotes are carriers. It shows criss-cross pattern of inheritance</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-06-genetics-evolution-principles-of-inheritance-variation-l-6_7-23inkiossh8-053-0633.6.jpg"></p>
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<h3 id="successphenylketonuriasuccess"><Success>Phenylketonuria</Success></h3>
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<ul>
<li>Inborn error in metabolism</li>
<li>Caused due to autosomal recessive gene</li>
<li>Lacks the enzyme (phenylalanine hydroxyalase) that converts phenylalanine to tyrosine</li>
<li>So phenylalanine get accumulated in the blood and converted into phenyl pyruvic acid and other derivatives</li>
<li>Accumulation of these in the brain causes mental retardation</li>
<li>It is excreted through the kidney</li>
<li>Urine turns into black when exposed to air</li>
<li>So known as black urine disease</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-06-genetics-evolution-principles-of-inheritance-variation-l-6_7-23inkiossh8-081-1522.8.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-06-genetics-evolution-principles-of-inheritance-variation-l-6_7-23inkiossh8-085-1746.0.jpg"></p>
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<h3 id="successchromosomal-disorderssuccess"><Success>Chromosomal disorders</Success></h3>
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<ul>
<li>Caused due to addition or deletion of chromosomes</li>
<li>Ploidy- Refers to the number of sets of chromosomes</li>
<li>Polyploidy Addition of many sets of chromosomes</li>
<li>Aneuploidy– Addition or deletion of a single chromosome from the normal diploid set</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-06-genetics-evolution-principles-of-inheritance-variation-l-6_7-23inkiossh8-089-2025.6.jpg"></p>
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<h4 id="successdowns-syndrome-autosomal-disordersuccess-1"><Success>Down’s syndrome (Autosomal disorder)</Success></h4>
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<ul>
<li>It is also known as Mongolism</li>
<li>Women above the age of 40 are likely to produce such children</li>
<li>It is due to non-disjunction of homologous chromosomes (21st chromosome)</li>
<li>A few victims live up to maturity and produce Mongolian and normal children at equal proportion</li>
<li>Individuals having Down’s syndrome are likely to develop leukaemia and Alzheimer’s disease</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-06-genetics-evolution-principles-of-inheritance-variation-l-6_7-23inkiossh8-089-2025.6.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-06-genetics-evolution-principles-of-inheritance-variation-l-6_7-23inkiossh8-15.jpg"></p>
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<h3 id="successsymptomssuccess-1"><Success>Symptoms</Success></h3>
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<ul>
<li>Short neck</li>
<li>Stubby fingers</li>
<li>Underdeveloped gonads and genetalia</li>
<li>A Mongolian type of eye lid fold</li>
<li>Flat nose</li>
<li>Permanently open mouth</li>
<li>Projecting lower lip</li>
<li>Protruding tongue</li>
</ul>
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<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-06-genetics-evolution-principles-of-inheritance-variation-l-6_7-23inkiossh8-18.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-06-genetics-evolution-principles-of-inheritance-variation-l-6_7-23inkiossh8-19.jpg"></p>
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