Transition 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,
Comprehensive Guide to Earth Science and Evolution
Continental Drift Theory
Paleontological 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 MoreFrom DNA to Protein: A Deep Dive into Protein Synthesis
The Polymerase Chain Reaction (PCR)
The polymerase chain reaction (PCR) is an artificial method of replicating DNA under laboratory conditions. The process involves the following steps:
- Denaturation: The DNA sample is heated (~90ºC) to separate the two strands.
- Annealing: The sample is cooled (~55ºC) to allow primers to anneal. Primers designate the specific sequence to be copied.
- Elongation: The sample is heated to the optimal temperature for a heat-tolerant polymerase (Taq) to function (~75ºC).