Notes, summaries, assignments, exams, and problems for Biology

DNA Replication: Definition and Mechanism

Definition: DNA replication is the process of producing two identical copies of DNA from one original DNA molecule. It is bidirectional and semiconservative—each daughter DNA contains one parental (old) strand and one new strand.

Steps of DNA Replication

1. Unwinding of DNA: Hydrogen bonds between base pairs break.
   • Two antiparallel strands separate, starting at the origin of replication.
   • The enzyme Helicase unwinds DNA, forming a replication fork.
2. Nucleotide Activation: Deoxyribonucleotides are activated using energy and the enzyme phosphorylase.
3. Strand Cutting and Stabilization: Endonuclease cuts the DNA at A-T rich regions (fewer hydrogen bonds).
   • Topoisomerase and helix destabilizing proteins stabilize the

The Human Heart: Structure and Function

The human heart, like other mammalian hearts, is a muscular pump with four chambers. The upper two chambers are the right atrium and the left atrium. The lower chambers are the right ventricle and the left ventricle. Both sides of the heart work simultaneously.

The walls of the atria are thinner than those of the ventricles. The right atrium receives deoxygenated blood from the body via the superior vena cava (collecting from the head, neck, arms, and chest) and the inferior vena cava (collecting from the lower parts of the body). The left atrium receives oxygenated blood from the lungs via the pulmonary veins.

After the blood enters both ventricles from the corresponding atrium, the deoxygenated blood in... Continue reading "Biological Systems: Heart Function, Genetics, and Plant Disease Management" »

• • Expert Testimony Standards: Evaluated under two landmark court cases:

    • Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993): Replaced the Frye general acceptance test. Establishes the trial judge as the "gatekeeper" who must ensure all scientific expert testimony is both relevant and reliable to exclude "junk science".

    • Kumho Tire Co. v. Carmichael (1999): Extended the judge's gatekeeping obligation and Daubert's reliability requirements to all expert testimony, including technical and other specialized non-scientific knowledge.

Scope of the Discipline and Professional Roles

• Forensic Anthropology: A sub-field of biological/physical anthropology that applies the principles of skeletal biology and anthropological theory to a medico-legal context. It

Biological Macromolecules

• Carbohydrates: Quick (short-term) energy source. Found in foods like; built from simple sugars (monosaccharides).
• Lipids: Long-term energy. Provide insulation and protection. Make up cell membranes. Include fats, oils, and waxes.
• Proteins: Made of amino acids. Help build structures (muscles, tissues). Act as enzymes to speed up reactions.
• Nucleic Acids: Store and transmit genetic information. Examples: DNA and RNA. Made of nucleotides.

Practice Questions

Energy Use During a Sprint

1. Which macromolecule would your body use first during a sprint? Why? Your body uses carbohydrates first because they provide quick, easily accessible short-term energy.

Macromolecules in Cell Membranes

2. Which macromolecule helps form your cell... Continue reading "Biological Macromolecules and Enzyme Functions" »

Chromosomes and DNA

Genes are contained within chromosomes, which are made of DNA and located in the cell nucleus. A chromosome contains thousands of genes. Every normal human contains 23 pairs of chromosomes, a total of 46 chromosomes.

Traits and Alleles

A trait is any gene-determined characteristic, often determined by more than one gene. Gene: A segment of DNA that controls a hereditary trait. Alleles are different versions of a gene that produce distinguishable traits in offspring. Two alleles must be present in order for a trait to appear in the offspring. One allele is provided by each parent to the offspring. When fertilization of sperm and eggs occurs, the new offspring will have 2 alleles for each gene.

Gregor Mendel's Contributions

Gregor... Continue reading "Genetics: The Basics of Heredity and Traits" »

Prokaryotic Cells: Bacteria

• Bacteria capsule: The outer jelly-like layer.
• Bacteria wall: The rigid structure that maintains cell shape.
• Fimbriae: Multiple short appendages used to attach to surfaces.
• Flagellum: A long appendage used for movement.
• Plasmid: A small ring of DNA.
• Ribosomes: Organelles that synthesize proteins.
• Nucleoid: The area where genetic material is concentrated.
• Cell membrane: A selective barrier.
• Cytoplasm: Everything inside the cell excluding the nucleus.

Eukaryotic Cells: Animal Cells

• Mitochondrion: Produces energy for the cell.
• Cell membrane: A selective barrier.
• Cytoplasm: Everything inside the cell excluding the nucleus.
• Nucleus: The site where ribosomes are made.
• Cytoskeleton: A network of protein filaments in the cytoplasm.
• Ribosomes:

The Human Eye: Structure and Function

• A spherical organ (approx. 2.3 cm) that allows us to perceive light, color, and depth.
• Key Parts:
  • Sclera: Outer white protective layer.
  • Cornea: Transparent front part that allows light entry.
  • Iris: Colored muscular part controlling pupil size.
  • Pupil: Opening through which light enters.
  • Lens: Flexible structure that focuses light onto the retina.
  • Retina: Light-sensitive layer converting light to electrical impulses.
    • Cones: Detect bright light and color.
    • Rods: Detect dim light and are responsible for night vision.
  • Optic Nerve: Transmits signals to the brain.
  • Blind Spot: Point where the optic nerve leaves the retina; no photoreceptors.

The Camera: Components and Operation

• An optical device that captures and stores images

Enzyme Function and Regulation: Key Terminology

• Enzyme: A biological catalyst, usually a protein, that speeds up a chemical reaction without being consumed.
• Substrate: The substance recognized by and binds to an enzyme, starting the catalysis process.
• Active Site: The pocket or groove in an enzyme where the substrate binds.
• Induced-Fit Model: A model describing how an enzyme changes shape to fit and accommodate the substrate, thus enabling catalysis.
• Cofactor: A non-protein group (often a metal ion) that binds to an enzyme, essential for its catalytic activity.
• Coenzyme: An organic molecule that acts as a cofactor (e.g., NAD+).
• Catalytic Cycle: Enzymes repeatably catalyze the conversion of substrates to products while remaining unchanged, illustrated

Master Exam Manual: CB 1.3 Genetic Variation

Chapter 1: Genetic Variation

1. Cells and Chromosomes

• The Nucleus as the Command Center: Eukaryotic cells isolate genomic material inside a double-membrane nucleus. This structure protects DNA from chemical damage caused by cellular metabolism.
• Chromosome Condensation: DNA does not float as loose strands. It wraps around spool-like proteins called histones. This complex coils into chromatin. During cell division, chromatin packs into visible, X-shaped structures called chromosomes.
• Karyotypes and Chromosome Pairs: Humans possess 46 chromosomes in total. They form 23 homologous pairs. One chromosome of each pair comes from the sperm (paternal); the other comes from the egg (maternal).
• Autosomes vs. Sex