CM 10

Introduction to Hybrid Fruits

• Definition of Hybrids: Crossbreeding between two plant species to create fruit with desirable characteristics.

• Distinction from GMOs: Hybrid fruits are not genetically modified organisms; they are produced without genetic engineering.

• Examples of Hybrids: Pluots (mostly plum) and apriums (mostly apricot).

Characteristics of Apricots vs. Plums

• Apricots: Smaller size, mealy flesh but good flavor.

• Plums: Larger, crisper flesh.

• Hybrid Goal: To create a fruit that combines the flavor of apricots with the texture of plums, enhancing taste and consumer enjoyment.

Hybrid Creation Techniques

• Back Cross Technique: This method is used to achieve a desired ratio in hybrids.

  • Example Breakdown:

    • Start with 100% apricot, cross with a plum (50% plum, 50% apricot in F1).

    • To create an aprium (75% apricot, 25% plum), backcross the F1 generation back to apricot:

      • 75% plum (from prior backcross) + 25% apricot = 75% apricot in the next generation.

• Variation Control: By continuing to back cross, different ratios of plum and apricot can be achieved depending on market needs.

Evaluation of Hybrid Taste

• Taste Test Findings: In consumer tests, apriums often outperform traditional plums in taste preference due to their favorable attributes, leading to broader acceptance.

Chromosomal Aberrations Overview

• Deletion: Loss of a chromosome segment.

• Duplication: Extra copies of chromosomal segments, which can lead to gene redundancy.

• Inversion: Segment of chromosome is flipped and reinserted, affecting gene order.

• Translocation: Segment of one chromosome breaks off and attaches to another chromosome.

  • Types:

    • Non-reciprocal: Piece moves from one chromosome to another without exchange.

    • Reciprocal: Two pieces exchange places between chromosomes.

Consequences of Chromosomal Changes

• Immediate Effects: Often have minimal consequences for the individual but can cause issues in reproduction, leading to infertility or genetic disorders.

• Formation Process:

  • Terminal Deletions: Portions of chromosomes are lost from the end.

  • Intercalary Deletions: Sections are lost from the middle of chromosomes, resulting in loops, making the chromosome unstable.

Unequal Crossing Over

• Mechanism: When homologous chromosomes align incorrectly during meiosis, leading to duplications on one chromosome and deletions on the paired chromosome due to mispairing of repetitive sequences.

• Resulting Variability: Can create diverse phenotypes and opportunities for evolutionary advantages.

Evolutionary Significance of Gene Duplications

• Utility of Duplications: Allow organisms to evolve new functions while preserving existing ones, acting as a buffer against harmful mutations.

  • Example: Duplication of ribosomal RNA genes increases protein synthesis capability.

  • Hox Genes: Particularly prominent in developmental biology; duplications have been crucial in the evolution of complex traits in animals.

Nucleotide Changes and Selection

• Single Nucleotide Polymorphisms (SNPs): Variations may or may not affect functions, depending on whether they confer an advantage or disadvantage.

• Copy Number Variants (CNVs): Implications include potential associations with human diseases like diabetes and autism, influencing genetic diversity and susceptibility.

Uniparental Disomy**

• Definition: Occurs when an organism receives two copies of a chromosome from one parent and none from the other due to nondisjunction.

• Consequences: Can lead to disorders caused by the expression of recessive alleles from the parent providing both copies.

• Examples of Syndromes:

  • Angelman Syndrome vs. Prader Willi Syndrome: Results of maternal versus paternal uniparental disomy, demonstrating how gene expression depends on parental origin.

Balancer Chromosomes

• Function: Prevent recombination in the regions they cover, facilitating genetic studies by ensuring specific alleles are maintained in experimental crosses.

• Use in Genetic Mapping: Crucial for studying gene functions, notably in model organisms like Drosophila (fruit flies).

  • Allows geneticists to track inheritance patterns across generations without losing mutations.

Conclusion and Implications

• Understanding hybridization, chromosomal changes, and genetic implications leads to significant insights into developmental biology, evolutionary genetics, and the mechanisms underlying complex traits and disorders.