Chromosomes, DNA Replication, and Genetic Processes
Chromosomes
Chromosomes are small, filamentous, rod-shaped structures that appear when a cell is dividing.
Parts of a Chromosome
- Chromatids: Two chromatids joined at the centromere form a chromosome.
- Telomeres: The terminal part of a chromosome, associated with aging and cellular senescence.
- Secondary Constriction and Satellites: Specific regions on some chromosomes.
Types of Chromosomes
- Metacentric: The centromere is in the center, and the two arms are equal.
- Submetacentric: The centromere is slightly
Theories of the Origin of Life and Evolution
Early Theories About the Origin of Life
Creation
Religious texts, from the Bible or the Koran to the Hindu Vedas, each in its own way describes the origin of the world and living beings. Most of them describe creations made by a creator, God, or spirit, who acts on the matter or creates humans from the earth or rock.
Spontaneous Generation
Aristotle was the great synthesizer of ideas about spontaneous generation. He believed that certain beings could not only be engendered from their parents but also
Read MoreFundamentals of Biology: Cells, Metabolism, and Diet
What is Biology?
Biology is the study of living organisms, their structure, evolution, functioning, distribution, and interrelationships. The term “Biology” derives from two Greek words: Bios, meaning life, and Logos, meaning study.
What are Biologists?
Biologists are scientists who conduct research related to this natural science. They study the structure, function, growth, origin, evolution, and distribution of living organisms.
Where Do Biologists Work?
Biologists work in a variety of settings, including:
Read MoreEndocrine System and Human Reproduction: Key Concepts
Key Points for Exam on the Endocrine System
Types of Chemical Communication
- Endocrine signaling: Uses hormones to regulate metabolism and homeostasis over a longer duration, requiring blood supply for transmission.
- Neurohormone signaling: Bridges the nervous and endocrine systems, where hormones are secreted into the bloodstream by neurons.
Hormone Properties and Functions
- Water-soluble hormones:
- Stored in vesicles, released via exocytosis.
- Travel freely in blood and bind to membrane receptors, triggering
Protein Structure and Properties: A Comprehensive Look
Primary Structure of Proteins
The primary structure is the most basic form of protein organization. It is determined by the amino acid sequence of the protein chain, i.e., the number of amino acids and the order in which they are linked by peptide bonds. The amino acid side chains extend from a main chain. By convention, the order of writing is always from the amino-terminal to the carboxy-terminus. A characteristic zigzag in their disposal is due to the planarity of the peptide bond rotation that
Read MoreHuman Nervous, Endocrine, and Reproductive Systems
The Human Nervous System
The nervous system in humans is, from a human point of view, the most perfect machine known. It consists of a central nervous system and a peripheral nervous system. The central nervous system consists of the brain and spinal cord.
Brain Development
The brain consists of three initial vesicles: the forebrain, midbrain, and hindbrain. Later, in embryological development, five vesicles originate by subdivision:
- The forebrain gives rise to the telencephalon and diencephalon.
- The