Describe three methods of gene transfer in Prokaryotes

Describe three methods of gene transfer in Prokaryotes. Describes stages of Meiosis and what happens in each stage? What are the four distinct phases of cell cycle? Describe their functions.

The correct answer and explanation is:

Gene Transfer in Prokaryotes

1. Transformation: This is the process where a prokaryotic cell takes up naked DNA from its surroundings. The DNA may come from other cells that have lysed. The foreign DNA is incorporated into the recipient’s genome, allowing for genetic changes such as new traits, antibiotic resistance, or virulence factors.
2. Conjugation: In conjugation, two prokaryotic cells form a direct connection via a structure called a pilus. One cell, typically a donor, transfers a plasmid (small, circular DNA) or part of its chromosome to the recipient cell. This process often involves the transfer of genes that confer antibiotic resistance or other beneficial traits.
3. Transduction: This method involves the transfer of genetic material between prokaryotic cells via a bacteriophage (virus that infects bacteria). The bacteriophage accidentally incorporates bacterial DNA during infection and later introduces it into a new bacterial cell. This can result in genetic variation and the spread of traits such as pathogenicity.

Stages of Meiosis

1. Prophase I: Homologous chromosomes pair up and exchange segments through a process called crossing over. This increases genetic diversity. The nuclear membrane dissolves, and spindle fibers begin to form.
2. Metaphase I: The homologous chromosomes align along the cell’s equator. This alignment is random, contributing to genetic variation. Spindle fibers attach to the centromeres of each chromosome.
3. Anaphase I: Homologous chromosomes are pulled to opposite poles of the cell. Unlike in mitosis, sister chromatids do not separate in this stage.
4. Telophase I: The cell prepares to divide, and two new nuclei form, each containing a haploid set of chromosomes. The cell undergoes cytokinesis, leading to two daughter cells.
5. Prophase II: The nuclear membrane dissolves again, and a new spindle apparatus forms in both daughter cells.
6. Metaphase II: Chromosomes align at the center of each cell. This is similar to metaphase in mitosis but with half the number of chromosomes.
7. Anaphase II: The centromeres divide, and sister chromatids are separated to opposite poles.
8. Telophase II: New nuclear membranes form around each set of chromosomes. Cytokinesis occurs, resulting in four non-identical haploid cells.

Phases of the Cell Cycle

1. G1 (Gap 1): This phase is the first stage of the cell cycle. During G1, the cell grows in size, produces RNA, and synthesizes proteins necessary for DNA replication. It is a time of cell metabolism and preparation for DNA synthesis.
2. S (Synthesis): In the S phase, DNA replication occurs, ensuring that each daughter cell will receive an identical copy of the genome. Chromosomes are duplicated, but they remain in the form of chromatin.
3. G2 (Gap 2): The cell continues to grow and prepare for mitosis. Organelles are replicated, and proteins required for cell division are synthesized. The cell checks for any DNA damage before proceeding to mitosis.
4. M (Mitosis): This phase involves the actual division of the nucleus. Mitosis is subdivided into prophase, metaphase, anaphase, and telophase, followed by cytokinesis, where the cytoplasm divides, resulting in two genetically identical daughter cells.