Grade_12_2nd_Sem_Lesson_1___2

General Biology 2

Key Topics Covered:
- Genetic Engineering
- History of Life on Earth
- Mechanisms of Change
- Evolution and Origin of Biodiversity: Patterns of Descent with Modification
- The Development of Evolutionary Thought
- Evidences of Evolution

Definition:
- Genetic engineering is the artificial manipulation, modification, and recombination of DNA or other nucleic acid molecules. This involves modifying organisms or populations of organisms (Britannica, T. Editors of Encyclopedia, 2020).
Techniques:
- Techniques used include artificial selection and biomedical interventions.
- Common examples:
  - Artificial insemination
  - In vitro fertilization (e.g., "test-tube" babies)
  - Cloning
  - Gene manipulation
Recombinant DNA Technology:
- The term has become more specific to recombinant DNA technology (gene cloning), where DNA molecules from two or more sources are combined and inserted into host organisms (Britannica, T. Editors of Encyclopedia, 2020).
Process:
- Genetic engineering modifies the genetic makeup of an organism using molecular techniques:
  1. Introduction of new traits
  2. Enhancement of a current trait by increasing gene expression
  3. Enhancement of a current trait by disrupting gene expression inhibition

In Medicine:
- Drug Production:
  - Insulin production using E. coli through gene splicing (Lumen, 2019).
- Hormones:
  - Human growth hormone for treating dwarfism from genetically-engineered bacteria.
  - Gene therapy for genetic diseases (Lumen, 2019).
In Research:
- Understanding gene functions through genetic engineering.
In Industry:
- Transformation of microorganisms like bacteria or yeast with gene coding for proteins.
In Agriculture:
- Creation of genetically-modified crops and organisms.

Definition:
- PCR is a common lab technique to amplify millions or billions of copies of a specific DNA region (Khan Academy, 2021).
Process:
- Repeated temperature changes to produce copies of the DNA target region (Khan Academy, 2021).

Purpose:
- The goal is to produce sufficient target DNA for analysis or further experimentation (General Biology, 2020).
Requirements:
- DNA polymerase enzyme (typically, Taq polymerase) is used to synthesize new DNA strands from templates.
- Taq polymerase requires primers for DNA synthesis, which are short sequences of nucleotides (approximately 20 nucleotides long).

Denaturation (96°C):
- Heating separates DNA strands to produce single-stranded templates.
Annealing (55°-65°C):
- Cooling allows primers to bind to complementary sequences on single-stranded DNA.
Extension (72°C):
- Raising the temperature allows Taq polymerase to extend the primers and synthesize new DNA strands.

Precambrian Era:
- Key events include Earth formation, evolution of eukaryotic cells, atmospheric oxygen increase, and development of multicellular organisms.
Paleozoic Era:
- Notable events:
  - Explosion of multicellular diversity and mass extinction (90% of marine species).
  - Divided into six periods (Cambrian to Permian).
Mesozoic Era:
- Known as the Age of Dinosaurs; divided into Triassic, Jurassic, and Cretaceous periods.
Cenozoic Era:
- Further divided into Tertiary and Quaternary periods; significant climate and organismal changes.

Formation of Earth, evolution of multicellular organisms, and the existence of microscopic bacteria and algae (3.5 billion years ago).

Major explosion in diversity of life forms and large mass extinction events.
Division into six periods:
- Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.
Establishment of plants and amphibians on land during the period.

Major evolutionary changes and occurrences in dinosaurs and marine life.
Concluded with extinction events attributed to various geological and cosmic phenomena.

Characterized by significant evolutionary expansion of mammals and flowering plants post-mass extinction at the end of the Cretaceous period.