Science Lecture Notes: Heredity, Inheritance, and Variation

Introduction

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Key Concepts

Heredity

• Definition: Transmission of genetic characters from parents to offspring.
• Characteristics and potentialities are derived from one generation to the next.
• Example: Child inherits traits like eyes, nose, hair color from parents.

Inheritance

• Definition: Acquisition of genetic qualities by offspring through sexual reproduction.
• Genetic materials from two parents are combined.
• Dominance of certain genes affects trait expression.
• Example: Child inherits specific traits from both parents.

Genetic Variation

• Definition: Differences between individuals or populations in traits and characteristics.
• Influenced by genetic differences.
• Example: Variation in eye color (blue, brown, green).

Genetic Vocabulary

Phenotype

• Definition: Observable physical properties of an organism (appearance, development, behavior).
• Examples: Pointed nose, blue eyes, straight hair.

Genotype

• Definition: Complete set of heritable genes in an organism.
• Represented by pairs of letters.
• Examples:
  • Pointed nose: NN
  • Blue eyes: Bb
  • Straight hair: SS

Alleles

• Definition: Alternative forms of a gene.
• Represented by letters (capital for dominant, lowercase for recessive).
• Examples:
  • NN (pointed nose)
  • Bb (blue eyes)
  • SS (straight hair)

Dominant and Recessive Traits

• Dominant Traits:

  • Traits that appear in offspring if contributed by a dominant allele.
  • Represented by capital letters.
  • Example: BB (brown eyes), DD (dimpled).

• Recessive Traits:

  • Weak traits that do not appear in phenotype of heterozygous individuals.
  • Represented by lowercase letters.
  • Example: bb (blue eyes), dd (no dimple).

Homozygous vs. Heterozygous Traits

• Homozygous Traits:
  • Made up of two same alleles.
  • Examples: AA, ff, gg.
• Heterozygous Traits:
  • Made up of two different alleles.
  • Examples: Aa, Ff, Gg.

Example of Trait Representation

• Dominant:
  • BB (brown eyes)
  • DD (dimpled)
• Recessive:
  • bb (blue eyes)
  • dd (no dimple)

Practice Question

• Scenario: Father has tall height, mother is short.
• Question: What trait does the child inherit from the father?
  • Options:
    • A) Dominant Trait
    • B) Recessive Trait
• Encourage viewers to comment their answers.

Conclusion

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• Invitation to the next lesson.