Understanding Cell Division: From Binary Fission to Mitosis
Binary Fission in Prokaryotes
Binary fission is the process used by most prokaryotes for asexual reproduction. Here are the major phases:
- DNA Replication: The circular DNA molecule replicates, starting at the origin of replication and proceeding in both directions.
- Chromosome Attachment: The two resulting chromosomes attach to the cell membrane.
- Cell Elongation: The cell grows and elongates, pushing the chromosomes apart.
- Cytokinesis: The cell membrane pinches inward, and a new cell wall forms, dividing
Kidney Function, Osmoregulation, and Adaptations for Water Conservation
Kidney Function and Osmoregulation
Ultrafiltration
The Bowman’s capsule, glomerulus, proximal convoluted tubule (PCT), and distal convoluted tubule (DCT) are located in the cortex of the kidney. The loop of Henle and collecting duct are located in the medulla. Kidneys are located in the abdominal cavity and receive oxygenated blood from the renal artery. Amino acids can’t be stored in the body and must be deaminated in the liver to urea via the ornithine cycle. Urea then diffuses into the blood and
Read MoreTransition from Fetal to Neonatal Circulation: Understanding the Changes at Birth
Chapter 1: Transition from Uterine to Extrauterine Life – Placental Circulation
Placental Circulation
Survival of the fetus requires a circulatory link between the mother and the embryo. Chronic Villi: are finger-like projections that arise from the embryo’s aorta within a week of uterine implantation and invade the uterine endometrium. These projections are filled by maternal blood bathing the fetal capillaries in an oxygen and nutrient-rich environment. The maternal uterine tissues and blood vessels
Read MoreComprehensive Guide to Earth Science and Evolution
Continental Drift Theory
Paleolithic evidence: Identical fossils of land-based organisms were found in continents situated far apart.
Geological evidence: Continents fit together along their coastlines and continental shelves. Rocks of the same age and type appear on each side of the line where they were joined.
Paleoclimatic evidence: Continents situated in the South Pole of Pangea have glacial moraines from the same age.
Wilson Cycle
Two cyclical processes of rifting and reuniting of supercontinents
Read MoreMutations and Genetic Variation
Mutations
Mutations alter DNA sequences and are the basis of alleles, the source of genetic variation in populations (fuel for evolutionary change), the cause of genetic diseases and disorders, and useful tools for understanding biological processes.
Mutations occur in somatic and germ cells, but only germline mutations are passed down to offspring.
Types of Mutations Based on Protein Function
- Gain-of-Function (GOF) Mutations: Increase gene/protein activity or produce new activity. Often dominant. Example:
Understanding the Cell Cycle and Mitosis
The Cell Cycle
The first stage of cell division is interphase, which is divided into three phases: G1, S, and G2. During interphase:
- DNA is present as uncondensed chromatin (not visible under a microscope).
- DNA is contained within a clearly defined nucleus.
- Centrosomes and other organelles have been duplicated.
- The cell is enlarged in preparation for division.
Phases of Interphase
- G1 (Gap phase 1): The cell grows larger.
- S (Synthesis): The genome is replicated.
- G2 (Gap phase 2): The second growth phase,