Operon Model: Regulation of Gene Expression in E. coli
Operon Model: Regulation of Gene Expression
Operon Model: Studies on the control of mRNA synthesis from initiation and the glucose effect observed in Monod’s work (1947) revealed that when glucose was added to a bacterial culture of E. coli containing lactose, the level of galactosidase significantly decreased.
This enzyme, galactosidase, separates lactose into its components: galactose and glucose. If bacteria are growing and glucose is added to the medium, the need to break down lactose decreases,
Read MoreHuman Reproduction: Stages, Development, and Challenges
Human Reproduction: An Overview
1) The Reproduction of the Human Being
Humans reproduce sexually. Women produce ova (eggs), and men produce spermatozoa (sperm). These two cells bind to form a zygote. Fertilization is internal; the egg and sperm bind within the female reproductive tract. The process of reproduction includes the following stages:
- Gamete production
- Fecundation (fertilization)
- Development of the zygote
- Delivery of the baby
- Child development
Changes Toward Sexual Maturity
2) Changes Toward Sexual
Read MoreCytokinins: Definition, Biosynthesis, Effects, and Agricultural Uses
Unit 19: Cytokinins
Definitions
Cytokinin: A group of plant hormones that promote cell division and cell differentiation. They are derived from the purine base, adenine, and have an aromatic substituent on nitrogen in position 6 of the purine ring.
Anticytokinin: Compounds that reversibly inhibit the activity of cytokinins.
Kinetin: The first cytokinin discovered, derived from autoclavable herring sperm DNA.
Cytokinin Oxidase: An enzyme that regulates the endogenous levels of cytokinins in plants.
Bioassays
Read MoreEvolution Theories: Lamarck, Darwin, and the Modern Synthesis
Lamarck’s Theory of Evolution
Inheritance of Acquired Characteristics: This theory posits that modifications acquired by parents during their lifetime are passed on to their offspring.
Lamarck observed that fossils in deeper strata represented simpler life forms, while surface strata contained more complex organisms, suggesting a progression from simple to complex life.
He argued for the existence of a biological evolution process where primitive forms gave rise to better-organized life forms.
Lamarck’
Read MoreChromosome Mutations: Number and Structure Variations
Lecture 15: Chapter 8
Chromosome Mutations: Variation in Number and Arrangement
Visualizing Chromosomes
Cytogenetics: The study of chromosomes within cells.
Chromosomes are designated based on the relative placement of their centromere. (See Figure 2.3 for visualization).
Human Karyotypes and idealized banding patterns group chromosomes: A(1-3), B(4-5), C(6-12), D(13-15), E(16-18), F(19-20), G(21-22).
Chromosome Numbers
Key terms include Aneuploidy, Euploidy, and Polyploidy. (Refer to Table 8.1 for examples)
Read MoreNeurons, Hormones, and Nervous System Function
Synapses and Neurotransmitters
Synapses are connections between neurons that transmit nerve impulses. A neurotransmitter is a chemical substance that produces the nerve impulse across the synapse.
Neuron Structure
Neurons possess filamentous extensions that facilitate connections with other neurons and organs throughout our body. We distinguish two main parts:
- Soma: Contains the nucleus and the main part of the cytoplasm.
- Extensions: There are two types:
- Dendrites: Short and highly branched extensions