152. Linkage disequilibrium (LD) decay is:
1. Much rapid in out-crossing than in selfing species
2. Much rapid in selfing than in out-crossing species
3. Equal in selfing and out-crossing species
4. Not dependent on selfing or out-crossing

Question

Linkage disequilibrium (LD) decay is:

1. Much rapid in out-crossing than in selfing species

2. Much rapid in selfing than in out-crossing species

3. Equal in selfing and out-crossing species

4. Not dependent on selfing or out-crossing

Detailed Explanation

Linkage Disequilibrium (LD) refers to the non-random association of alleles at different loci on a chromosome. This concept is crucial in genetic studies, particularly when analyzing genetic variation and mapping quantitative traits. LD decay refers to the decrease in linkage disequilibrium between loci as the genetic material undergoes recombination over generations. Understanding how LD decay behaves differently in various breeding systems—such as selfing and out-crossing species—is important for interpreting genetic data and predicting evolutionary processes.

Linkage Disequilibrium and Recombination

• Linkage disequilibrium can persist over generations depending on several factors, including:

  • Recombination rates: The frequency of genetic recombination during meiosis, which breaks down LD by separating linked alleles.

  • Genetic drift and selection: These evolutionary forces can either maintain or break down LD depending on their influence on the population.

In general, LD decay describes how the association between alleles decreases as the genetic material recombines over successive generations.

Selfing vs. Out-Crossing Species

1. Selfing Species:

   • Selfing species are those where individuals primarily reproduce with themselves (e.g., plants that self-pollinate).

   • In selfing species, recombination is often limited because the population experiences less genetic mixing between individuals. As a result, LD decay occurs more slowly, and LD tends to persist over many generations.

   • In these species, the rate of recombination is lower, and the genetic material stays relatively unchanged over generations, allowing LD to be maintained for longer periods.

2. Out-Crossing Species:

   • Out-crossing species are those where individuals reproduce with genetically distinct individuals (e.g., many animals and some plants).

   • In out-crossing species, recombination occurs more frequently between diverse genetic backgrounds, which leads to faster LD decay. Because these species undergo more genetic mixing, the alleles associated with each other will gradually become unlinked over multiple generations, causing LD to break down more rapidly.

Correct Answer and Explanation

The correct answer is:

1. Much rapid in out-crossing than in selfing species

Explanation:

• In out-crossing species, LD decay happens more rapidly due to the higher frequency of recombination events that separate linked alleles over time. The genetic material is more genetically diverse, leading to a faster breakdown of LD.

• In contrast, selfing species experience slower LD decay because their genetic recombination is less frequent, leading to more persistent associations between alleles over generations.

Conclusion

Linkage disequilibrium decay is a key process in understanding how genetic variation is inherited and evolves over time. The rate of this decay is significantly faster in out-crossing species compared to selfing species, due to higher rates of recombination and genetic diversity in out-crossing populations. Understanding these differences is essential for interpreting genetic studies and evolutionary patterns in different species.