DNA, Genes, and Biotechnology: A Deep Dive
Protein Synthesis
Protein synthesis takes place in the cytoplasmic ribosomes. A ribosome has two sites for tRNA entry.
- The ribosome binds to the mRNA. The initiator codon occupies the P site, and the following codon occupies the A site. The first codon then joins its complementary anticodon on the tRNA.
- The tRNA carrying the anticodon complementary to the codon in the A site moves into the A site.
- Once both tRNAs are in position, a ribosomal enzyme joins the two amino acids.
- The tRNA in the P site, now without its amino acid, leaves the ribosome. The ribosome moves along the mRNA so that the tRNA previously in the A site now occupies the P site. A new tRNA with the anticodon complementary to the next mRNA codon arrives at the A site.
- The amino acid on the tRNA in the A site attaches to the growing amino acid chain on the tRNA in the P site. This process continues. At the end of the mRNA, a codon without a complementary tRNA signals the termination of the process.
The Human Genome Project
Goals:
- Identify and locate genes on chromosomes, especially those causing hereditary diseases.
- Determine the nucleotide sequence of each gene.
- Determine gene function by comparing sequences with genes of known functions.
- Identify genes encoding specific proteins and determine their roles in diseases.
Key Findings:
- The number of human genes is approximately 30,000.
- Humans share many genes with bacteria and other simple organisms.
- There is little difference between the genomes of any two individuals.
Biotechnology and Genetic Engineering
Genetic engineering, a branch of biotechnology, involves manipulating and transferring DNA between organisms to create new varieties or correct genetic defects. The process begins with cloning a gene. This gene, which encodes a protein, is combined with small molecules called a cloning vector to form recombinant DNA. The resulting organism is called transgenic.
Plasmids and viral DNA (like bacteriophages) are common cloning vectors. These vectors are introduced into host cells (bacteria or yeast), creating a population of cells that produce the protein encoded by the introduced gene.
Applications:
- Production of substances in transgenic plants, animals, and even molecules for producing plastics.
- Insect resistance in plants by introducing a bacterial gene encoding a harmless insecticide protein.
- Increased growth rates in animals, such as salmon with an introduced gene allowing for rapid growth and tolerance to low temperatures.
Cloning Applications
Livestock Cloning: Allows replication of high-performing animals.
Species Conservation: Enables cloning of endangered species.
Medicine: Provides a tool for studying embryonic development and analyzing cellular changes in cancer.
Human Cloning
Human cloning has two potential uses: reproductive and therapeutic.
Reproductive Cloning: Creating human beings is prohibited.
Therapeutic Cloning: Aims to produce stem cells for research and therapeutic purposes. This involves creating a cloned embryo from a donated cell nucleus introduced into an oocyte. This technique could potentially restore damaged organs or tissues.
Bioethics
General Bioethics: Establishes the ethical values and principles guiding moral judgments.
Special Bioethics: Addresses specific issues like embryo manipulation, abortion, and genetic engineering. These two branches are interconnected, as general ethical considerations influence specific applications.
Chromosomes
DNA, a large molecule within the cell nucleus’ chromatin, condenses to form chromosomes.
DNA’s Double Helix
DNA consists of two chains wound around the same axis.
Ribosomes
mRNA interacts with tRNA within ribosomes, matching mRNA codons with tRNA anticodons one by one.