This tutorial deals with the introduction to Genetics. 1. Introduction to Genetics 2. Variations: Somatic and Blastogenic Variations (Continuous and Discontinuous {Meristic and Substantive} variations 3. Types of genetics 4. Blending inheritance 5. Pre-Mendelian Theories 6. Atavism 7. Evidence in favor of Blending Inheritance: 8. Terminologies related to Genetics.

1. Genetics 1.1: Introduction
Presented by Dr. Roman Saini

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3. Introduction to Genetics
• "Genetics" term by Bateson. Father - "Gregor John Mendel".
• Genetics: Branch of biology dealing with the inheritance as well as the
variation of characters from parents to offspring.
• Inheritance:
• Process by which characters are passed on from parents to progeny.
• Basis of heredity.
• Variation: Degree by which progeny differ from their parents.

4. Variations
1. Somatic Variations:
• Non-inheritable variation.
• Occurs in somatic cell.
• E.g. Hair length of human being.
2. Blastogenic or Germinal Variations:
• Inheritable variation.
• Occurs at germplasm level or in reproductive body part.

5. 2 types of Blastogenic variations
1. Continuous Variations: Occurs due to crossing over or genetic
recombinations.
2. Discontinuous Variations: Sudden genetic changes in reproductive
cells due to environmental fluctuations. Known as Mutations or
Saltations. Two types-
• Meristic Variations: Change in quantity.
• Substantive Variations: Change in quality, e.g. polydactyl.

6. Types of Genetics
• Classical or Transmission Genetics: Fundamental study of genetics.
Involves study of transfer of characters.
• Forward Genetics: Phenotype Protein RNA DNA.

7. Types of Genetics
• Reverse Genetics: DNA RNA Protein Phenotype.
• Population Genetics: Study of distribution of a particular gene in
population with respect to its dominant and recessive traits.
• Molecular Genetics: Study of genetics at molecular level. Three
aspects- Structural Genetics, Functional Genetics and Applied
Genetics.

8. Blending Inheritance
Pre-Mendelian Ideas. Includes-
• Moist Vapor Theory by Pythagoras.
• Reproductive Blood Theory by Aristotle.
• Homunculus or Pre-formation Theory by Swammerdam.
• Theory of Pan-genesis by Darwin.
• Weismann's Theory.

9. Exception of Blending Inheritance:
• Atavistic Characteristic: Characters which are observed in some
offspring but they are not present in their parents. Ancestral
characteristic.

10. Evidences in favor of Blending Inheritance:
• Incomplete dominance of Mirabilis Jalapa for flower color.
• Polygenic inheritance of skin color, human intelligence, human
height, they sometime exhibit blending.

11. Terminology
• Character: Expressible form of any phenotype.
• Contrasting character: Character having more than one variant. All
characters are not contrasting characters.
• Trait: Detectable variant of a character.
• Gene or Factor: Unit of inheritance. Contain information that is
required to express a particular trait in an organism.

12. • Allele: Different forms of the same gene coding for a pair of
contrasting traits.
• Homozygous: Having two identical alleles of a gene e.g. TT or tt.
• Heterozygous: Having two different alleles of a gene e.g. Tt.
• Monohybrid Cross: Cross applied for one character only.
• Dihybrid Cross: Cross applied for two characters.

13. • Dominant: Phenotypic expression which can express itself in
homozygous as well as heterozygous combination by suppressing
expression of another trait.
• It is designated by capital letter.
• Recessive: Phenotypic expression which can express itself only in
homozygous combination.
• It is designated by small letter.

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