Embryonic Development and Biotechnology Principles
Key Stages in Embryonic Development
The union of sperm and egg creates the zygote, marking the beginning of embryonic development.
Key Developmental Milestones
- Implantation: The embryo attaches to the endometrium (lining of the uterus). Approximately 70% of zygotes and early embryos are eliminated naturally, ensuring only the fittest reach the end of gestation.
- Nervous System Formation: During the third week of pregnancy, the neural plate forms on the surface ectoderm. This structure develops into two configurations: the neural tube (central nervous system) and the neural crest (peripheral nervous system).
- Myelination and Growth: By mid-pregnancy, neurons begin to be covered in myelin. This process continues through the first two years of life, alongside the growth of axons, dendrites, and the development of synapses.
Organ Development Timeline
- Months 1-2: Limb buds appear; the heart begins to beat on day 25; the neural tube, brain, and spinal cord develop; eyelids are sealed.
- Months 3-4: Soft nails form; the heartbeat is audible; skin appears pink.
- Months 5-6: Skin becomes wrinkled; lungs are immature; eyelids open.
- Months 7-8: The fetus can respond to light; bones become soft and flexible.
- Month 9: The fetus is fully developed and ready for birth.
Gene Therapy and Genetic Disorders
Gene therapy utilizes genetic material to treat inherited and acquired diseases by replacing mutated DNA with normal sequences.
Types of Genetic Conditions
- Chromosomal: Conditions such as Down syndrome (extra chromosome 21).
- Monogenic: Disorders caused by a single gene, such as cystic fibrosis.
Preimplantation Diagnosis: Genetic screening performed before the embryo is implanted.
Risks of Biotechnology
Genetically Modified Organisms (GMOs) present several concerns:
- Loss of genetic diversity.
- Horizontal gene transfer via transposons (DNA fragments that jump between species).
- Potential adverse health effects, such as allergies.
Gene Cloning Techniques
Cloning allows for the duplication of DNA fragments in a test tube, producing millions of identical molecules.
The Cyclic Reaction Process
- Denaturation: The DNA molecule is heated to separate the two strands.
- Annealing and Extension: Each strand is copied by DNA polymerase. We use the enzyme from the bacterium Thermus aquaticus, which remains stable at high temperatures.
- Cycling: The newly formed chains are separated by heat, and the cycle repeats to amplify the DNA.