DNA Technologies

Introduction: The vital function of DNA replication is to ensure genetic stability in organisms. Understanding genetic similarities and variations is crucial for comprehending evolutionary relationships and conserving biodiversity. Technologies like DNA sequencing reveal genetic connections and play a significant role in conservation efforts.

DNA Sequencing and Profiling Technologies

Overview of Sequencing Technologies

• Definition: DNA sequencing identifies the order of nucleotides in DNA, essential for understanding genetic information.
• Historical Context:
  • 1970s: Introduction of the Sanger sequencing method, which transformed genetic research.
  • Next-Generation Sequencing (NGS): Represents recent advancements in DNA sequencing technology.

DNA Replication Process

• Initiation:
  • Begins at specific sites called origins.
  • Helicase unwinds the DNA double helix.
• Elongation:
  • DNA Polymerase incorporates nucleotides to extend new strands.
  • Leading Strand: Synthesised continuously.
  • Lagging Strand: Forms Okazaki fragments, joined by ligase.
• Termination: Completes when replication concludes, and proteins dissociate.

Reproduction and Continuity of Species

Sexual vs. Asexual Reproduction

Definition and Processes

• Sexual Reproduction: Involves meiosis.
  • Two rounds of cell division.
  • Introduces variation through recombination.
• Asexual Reproduction: Involves mitosis.
  • Produces clones and retains original chromosome numbers.

Genetic Variation

Sources of Variation

• Recombination: Occurs during meiosis, mixing alleles.
• Mutations: Random changes introducing new traits.

SNPs and DNA Technologies

Definition and Techniques

• SNPs: Single base pair variations crucial for genetic diversity.
• PCR: Technique for identifying SNPs.

Impact of DNA Errors and Repair

Role of DNA Repair Mechanisms

• Exonuclease: Removes incorrect bases to avoid mutations.
• Repair DNA Polymerase: Accurately fills in missing bases.
• Ligase: Seals gaps in the DNA backbone.

Impact of Errors on Protein Function

• Mutations: DNA sequence alterations affecting protein function.
  • Examples: Disorders like cystic fibrosis and sickle cell anaemia.

Population Genetics and Predictive Tools

Hardy-Weinberg Principle

• Concept:
  • Hardy-Weinberg equilibrium: Evaluates the stability of allele frequencies over time, assuming specific conditions.

Environmental and Genetic Interactions

• Gene-Environment Interplay: Influences phenotypes and adaptation strategies.

By understanding these processes, one gains insight into how species endure through genetic diversity and adaptability.

Worked Example: Hardy-Weinberg Principle Application

Let's calculate allele frequencies in a population:

Problem: In a population of 500 organisms, 360 show the dominant phenotype (AA or Aa) and 140 show the recessive phenotype (aa). Calculate the frequencies of alleles A and a.

Solution:

1. Frequency of recessive phenotype (aa) = 140/500 = 0.28
2. Therefore, q² = 0.28, so q = √0.28 ≈ 0.53 (frequency of allele a)
3. Since p + q = 1, p = 1 - 0.53 = 0.47 (frequency of allele A)
4. To verify: p² + 2pq + q² = (0.47)² + 2(0.47)(0.53) + (0.53)² = 0.22 + 0.50 + 0.28 = 1

This calculation helps us understand the genetic composition of the population and predict future genetic changes if evolutionary forces are applied.