Convergent Plate Boundaries and Cellular Genetics

Convergent Boundaries and Plate Tectonics

Convergent boundaries are where the edges of two plates are moving towards each other. The lithosphere is destroyed.

Three Types of Convergent Boundaries

1. Converging Continental and Oceanic Plates

At boundaries where a continental plate and an oceanic plate collide, a phenomenon called subduction takes place; in other words, the denser oceanic plate slides under the continental plate. The subducting plate sinks into the mantle and forms a trench. This sinking can be detected as the lithosphere rubs against the rocks in the mantle, causing earthquakes at many points of the Benioff zone, which is the surface of the sinking plate. The force of the plates raises the continental crust, creating a boundary mountain range (such as the Andes) that runs parallel to the convergent boundary.

2. Convergence Between Two Oceanic Plates

At boundaries where two oceanic plates collide, the denser (the oldest) subducts under the other. The sinking also forms a trench. The subduction melts the rocks in the mantle and creates magma that rises and creates a crescent-shaped set of volcanic islands called an island arc, such as the Aleutian Islands.

3. Convergence Between Two Continental Plates

At boundaries where two continental plates collide, neither of the plates sinks. The plates push together; the rocks fold, break, and rise up, forming a mountain range. The Himalayas were formed in this way when the Indian and Eurasian plates collided.

Understanding RNA and DNA

RNA (Ribonucleic Acid)

RNA is located in the nucleus and the cytoplasm of cells. RNA contains ribose, and the nitrogenous bases that form them are: Adenine (A), Guanine (G), Cytosine (C), and Uracil (U). RNA generally comprises a single chain of nucleotides.

DNA (Deoxyribonucleic Acid)

DNA is found in the nuclei of eukaryotic cells and in the cytoplasm of prokaryotic cells. DNA nucleotides contain deoxyribose, and they are formed by Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). DNA is made up of two chains of deoxyribonucleotides. Bonds between the nitrogenous bases of each chain keep them joined together. Each nucleotide in one chain is linked to a nucleotide in the other, which is its complementary base pair.

Cell Division: Mitosis vs. Meiosis

Mitosis

• Only takes place in somatic cells.
• Happens in both haploid and diploid cells.
• Is a short process.
• The nucleus divides once.
• There is no crossover.
• Sister chromosomes separate during the anaphase.
• Two identical daughter cells are formed with the same chromosomes as the mother cell.

Meiosis

• Takes place in germ cells.
• Happens only in cells with a diploid number of chromosomes.
• Is a long process.
• The nucleus divides twice.
• There is crossover between homologous chromosomes.
• In anaphase I, the homologous chromosomes separate.
• Sister chromosomes separate during anaphase II.
• Four genetically different daughter cells are formed with half the chromosomes of the parent.