Lecture Notes: Genetics and Inheritance

Introduction

• New platform introduced allows pausing and rewatching of videos.
• Resources and old exam questions will be shared.
• Focus on understanding genetics for Paper 2 (45 marks), crucial for exams.

Key Topics

• Genetics: Study of heredity and variation in organisms.
• Inheritance: Characteristics received from parents through genes.

Historical Background

• Gregor Mendel: Austrian monk who laid the groundwork for genetics through pea plant experiments.
• Pea plants chosen for quick growth and identifiable characteristics.
• Characteristics observed: seed shape, seed color, flower color, plant height.

Mendel's Experiments

• Self-pollination & Cross-pollination: Techniques used to study genetic traits.
• Mendel's Laws: Formulated from experiments.
  • Law of Segregation.
  • Law of Independent Assortment.

Definitions and Concepts

• Allele: Alternative form of the same gene. Different alleles from each parent.
  • Example: Chromosome carries allele for eye color; one allele for brown, another for blue eyes.

Genetic Terms

• Locus: Location of a gene on a chromosome.
• Homozygous: Both alleles for a trait are the same (e.g., red flower from both parents).
• Heterozygous: Alleles for a trait are different (e.g., red flower allele from one parent, blue from another).
• Dominant Trait: Stronger trait that overshadows recessive traits.
• Recessive Trait: Weaker trait, appears only if two copies are present.

Example: Pea Plants

• Tall plant (dominant) vs. short plant (recessive).
• Use of capital (T for tall) and lowercase (t for short) letters in genetic crosses.
• Dominant trait overshadows recessive; heterozygous plants show dominant traits.

Human Traits

• Dominant Traits: Cleft chin, widow's peak, brown hair, brown eyes.
• Recessive Traits: No cleft, straight hairline, blonde hair, blue eyes.

Genotype and Phenotype

• Genotype: Genetic makeup, not visible; determines traits like tall or short plants.
• Phenotype: Physical appearance determined by genotype.

Mendel’s Laws

• Law of Segregation: Chromosomes separate in meiosis, each cell gets a single allele.
• Law of Independent Assortment: Alleles for different traits segregate independently.

Conclusion

• End of first video.
• Encouragement to ask questions for further clarity.