Genetic Inheritance and Variability

Mendelian Inheritance and Flower Color

• Mendelian Concepts: Discussing traditional types of genetic inheritance defined by Mendel, specifically in flower color.
  • Crossing purple and white flowers results in all purple offspring, indicating dominance of the purple allele.
  • This can give the impression of blending, but is more complex in genetics.

Haploinsufficiency

• Definition: Haploinsufficiency occurs when one copy of a gene is not sufficient for normal function.
  • Example: White flowers have two copies of a broken pigment gene and the heterozygous (mixed color) offspring have one working gene, leading to less pigment than the homozygous red flowers.
• Key Point: Not all alleles blend; often, it indicates that a functional gene is lacking.

Blending vs. Codominance

• Blending Inheritance: Sometimes seen in traits where two different alleles result in an intermediate phenotype.
• Codominance: In this pattern, both phenotypes are expressed distinctly, such as in flower pigmentation where red and white are both visible.
  • Example: Blood types in humans represent codominance, where both A and B alleles can be expressed clearly.

Multiple Alleles and Interactions

• Multiple Alleles: Most genes have more than two alleles, contributing to diverse traits. Each change in the DNA sequence creates a new allele affecting protein function.
  • Example of Rabbit Coat Color:
  • Alleles include:
    • Capital C (dominant: full color)
    • Little cc (chinchilla: recessive to full, dominant to Himalayan and albino)
    • Himalayan (dominant to albino, recessive to chinchilla and full)
    • Albino (recessive to all)
  • Interactions: Some alleles can be recessive to one and dominant or codominant with another.

Genetic Mutations

• Mutations (e.g., nonsense mutations) can lead to changes in gene expression, resulting in new alleles that may affect phenotypes in various ways, altering protein function.

Quiz Preparation

• Next Quiz: Scheduled for next week on Wednesday, covering the same unit.
  • A detailed list of topics can be found on the Canvas portal under the quiz assignment.