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PRINCIPLES OF INHERITANCE AND VARIATIONS in 3 Hours | BEST for Class 12 Boards

NCERT Wallah・124 minutes read

Genetics focuses on heredity, inheritance, and variation, exploring factors that control traits and the significance of blending in future generations. Understanding genetic mechanisms, chromosome theory, and inheritance patterns is crucial for comprehending complex genetic traits and diseases like hemophilia and color blindness.

Insights

  • Genetics involves the transfer of traits from parents to offspring through non-random processes, focusing on additive and variation aspects to maintain individuality.
  • Understanding genotype and phenotype, along with the process of determining unknown genotypes through test crosses, is crucial for comprehending genetic inheritance patterns and the impact of mutations on gene expression.
  • The significance of polygenic inheritance, chromosomal theory, and the role of chromosomes in determining genetic traits are essential for grasping the complex mechanisms that control trait expression and genetic disorders.

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Recent questions

  • What is genetics?

    Genetics is the study of inheritance and variation.

  • What is heredity?

    Heredity involves transferring characteristics from parents to offspring.

  • What is Mendel's hybrid digestion experiment?

    Mendel's hybrid digestion experiment involved selecting pure parental traits.

  • What is the significance of factors in genetics?

    Factors in genetics are discrete units that control traits without blending.

  • What is polygenic inheritance?

    Polygenic inheritance involves multiple genes controlling a single character.

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Summary

00:00

Genetics: Inheritance, Variation, and Mendel's Experiment

  • Genetics is defined as a branch dealing with inheritance and variation.
  • Heredity involves the transfer of characteristics from parents to offspring.
  • Inheritance should not be transferred through a random process.
  • Genetics deals with additive and variation aspects.
  • Variation refers to the amount and degree of difference between parents and offspring.
  • Mendel's hybrid digestion experiment involved selecting pure parental traits.
  • Observations in the F1 and F2 generations showed matching traits from parents.
  • The number of particular progeny matching traits was a significant observation.
  • Factors in genetics are discrete units that control traits without blending.
  • Factors in pairs maintain individuality and directly control traits.

18:02

Genetic Inheritance and Test Crosses Explained

  • Gin is discussed, followed by a conversation on mental experiments known as Locke Dominance and loss of aggregation.
  • The concept of Inheritance is explained, involving lodges and divisions, with a focus on Dominant and Lord of Creation.
  • Factors present in Paris are mentioned, related to sexual reproduction in flowering plants.
  • The discussion shifts to the principal of Ingredients and molecular studies.
  • The text delves into the significance of factors like capital and blending, emphasizing the 50% chance of inheritance from parents.
  • The process of creating individuality through factors and the impact of blending on future generations is detailed.
  • The text explores the concept of genotype and phenotype, with a focus on Monohybrid processes and genotypic ratios.
  • Test Cross is explained as a method to determine unknown genotypes, highlighting the significance of capital and small letters in genetic inheritance.
  • The process of determining genotypes through test crosses is elaborated, emphasizing the 50% probability of inheritance.
  • The text concludes with practical advice on preparing for challenging questions related to genetic crosses and debits, stressing the importance of careful reading and understanding.

38:10

"Hybrid Cross Dance: Genotypes and Phenotypes Explained"

  • Hanak's formula is discussed, but it's noted that not everything can be determined by a formula.
  • Further methods need to be explained.
  • Before teaching about a hybrid cross dance, checking the debit card and cigarette is suggested.
  • The concept of hybrid cross is explained as connecting two characters in life.
  • The destruction of eyes by a planet is mentioned, specifically Devi's role in erasing capital.
  • Four debits will be made, and the games associated with them are to be written down.
  • Instructions on how to determine genotypes and phenotypes are provided.
  • The process of extracting genotypes from a given scenario is detailed.
  • The importance of understanding chromosome location and character traits is emphasized.
  • The concept of incomplete dominance is introduced, with examples like snapdragon flowers.

01:00:51

Genetic Crosses: Patterns in Plant Inheritance

  • Two types of plants are crossed, resulting in the F1 generation.
  • The F1 generation does not match both parent plants.
  • The F1 generation is crossed with a white plant.
  • In the F2 generation, three plants with different colors are obtained.
  • The plants in the F2 generation have different thicknesses in their petals.
  • The ratio of red to pink flowers is 1:4.
  • The white flowers have a secret ratio of 1:4.
  • The notification system is explained using specific numbers and patterns.
  • The text discusses the dominance of certain genes and the impact on enzyme synthesis.
  • The importance of understanding mutations and their effects on gene expression is highlighted.

01:23:21

Genetic Mechanisms: Polygenic Inheritance and Traits

  • Excess hydroxyl will convert into phenyl pyruvic acid, known as ketone bodies, leading to their presence in urine.
  • If ketone bodies are not reabsorbed in the kidney, they will be excreted in urine, potentially causing symptoms like mental retardation.
  • Mental retardation can manifest in various systems, along with decreased skin and hair pigmentation.
  • An example of recessive inheritance is the phenyl hydroxyl enzyme gene, which can lead to phenylketonuria.
  • Inheritance can exhibit dominance or incomplete dominance, affecting the expression of specific traits.
  • Polygenic inheritance involves multiple genes controlling a single character, leading to a range of variations in traits like eye color.
  • Quantity inheritance, a form of polygenic inheritance, results in traits being expressed based on the dominance of specific genes.
  • Polygenic inheritance is also known as quantitative inheritance, where the number of dominant genes influences trait expression.
  • Chromosomal theory explains how multiple genes interact to control various characteristics in individuals.
  • Understanding polygenic and quantitative inheritance is crucial for comprehending the complex genetic mechanisms that determine trait expression.

01:47:57

Chromosomal Theory of Inheritance: Mendel's Legacy

  • Chromosomal Theory of Inheritance of Gregor Mendel's work is discussed.
  • The theory focuses on the physical basis of inheritance and the concept of discrete units.
  • Mendel's work was published in 1965, but the results were not widely publicized until later.
  • The theory involves the understanding of chromosomes and factors in inheritance.
  • Chromosomes and factors are depicted as having legs in a diagram for comparison.
  • The independence and aggregation of chromosomes and factors are explained.
  • Experimental verification of inheritance was conducted by T.S. Maurya.
  • The importance of linkage on the same chromosome for genetic combinations is highlighted.
  • The concept of independent assortment and its impact on genetic variation is discussed.
  • The significance of linkage genes in determining genetic combinations is emphasized.

02:09:50

Understanding Linkage and Chromosomes in Genetics

  • The text discusses the concept of linkage and chromosomes, emphasizing the importance of understanding the relationship between genes on the same chromosome.
  • It mentions that if genes are on the same chromosome, new combinations can be formed, and the chances of crossing over increase.
  • The text explains that the distance between genes on a chromosome affects the likelihood of crossing over, with closer genes having fewer chances of crossing over.
  • It highlights that the chances of crossing over increase when the distance between genes is greater.
  • The text introduces the idea of recombinant, which is directly proportional to the frequency of crossing over.
  • It references a scientist named Morgan who developed a scale to represent the percentage of recombinants resulting from crossing over.
  • The text describes a genetic experiment involving Drosophila flies with different characters on the X chromosome, such as body color and wing shape.
  • It explains how the experiment involved crossing flies with different traits to observe the inheritance patterns of these traits.
  • The text details the process of determining dominant and recessive traits in the offspring of the genetic experiment.
  • It concludes by discussing the significance of understanding genetic inheritance patterns and the role of chromosomes in determining traits in offspring.

02:35:26

Genetic Settings and Traits: Instructions and Analysis

  • Instructions on writing genetic settings, including Ritesh Female and recessive female notation.
  • Mention of Vitamin A and Vitamin A in relation to genetic traits.
  • Reference to checking NCERT for second-class individuals and examining fund and F1 generations.
  • Explanation of X chromosome inheritance and eye color genetics.
  • Details on body color and eye color genetics, including dominant traits.
  • Advice to cross two characters at least 1 hour before determining results.
  • Discussion on the impact of distance on genetic recombinant percentage.
  • Explanation of sex determination through chromosome analysis.
  • Clarification on the significance of pedigree analysis in genetic studies.
  • Instructions on using symbols to represent genetic traits in pedigree charts.

02:56:45

Genetic Disorders: Disney, Bulls, and Pedigrees

  • Disney is compulsory for the father if the female has the disease
  • A bull will be received in the mail if affected, and another will come if the mail icon is affected
  • The female Lana must be the father of an actor
  • Kadhi should be made and tried to solve it
  • The female affected's ingredients should be wrapped in mail tea
  • The female affected's ingredients are effective
  • A pedigree can be created where both are normal and any of their children is affected
  • Hemophilia and color blindness are mentioned as genetic disorders
  • Sickle cell anemia and thalassemia differences are explained
  • Color blindness results in the inability to distinguish between red and green

03:18:35

Genetic Disorders: Color Blindness, Hemophilia, Down Syndrome

  • Blindness is more visible in males due to one X chromosome, leading to closer color gray perception and confirmation of color blindness through tests like the Ishihara test.
  • Hemophilia, a disease affecting blood clotting, requires factor thirteen for clotting cascade, with a lack of factors leading to increased clotting time and the condition being termed as Haemophilia.
  • Queen Victoria's lineage and the inheritance of hemophilia, particularly in females who are carriers but rarely affected, due to the X-linked nature of the disease.
  • Down syndrome, characterized by an extra chromosome, presents symptoms like an open mouth, low IQ, and distinct physical features, with the diagnosis based on genetic testing and identification of the additional chromosome.
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