Lecture Content

Exam Preparation Topics

• Cell Division: Understand the reasons cells divide, focusing on growth, repair, and reproduction. Cell division is essential for organism growth, tissue repair, and asexual reproduction. The two main types of cell division are:

  • Mitosis: A method of cell division that results in two identical daughter cells, enabling growth and tissue repair. It includes phases such as prophase, metaphase, anaphase, and telophase.

  • Meiosis: A specialized type of cell division that reduces the chromosome number by half, producing four genetically diverse gametes. This process is crucial for sexual reproduction, allowing for genetic variation through the combination of genetic material from two parents.

• Herd Immunity: Importance in public health and how it protects vulnerable populations. Herd immunity occurs when a significant portion of a population becomes immune to a disease, either through vaccination or previous infections, reducing its spread. This phenomenon protects those who cannot be immunized, such as individuals with certain health conditions. By achieving herd immunity, the overall risk of infection decreases, leading to community-wide protection.

• Sickle Cell Anemia: Definition and implications of being homozygous recessive for the trait. Sickle cell anemia is a genetic disorder caused by two copies of a mutated allele for hemoglobin (HbS). This mutation causes red blood cells to form a sickle shape, leading to blockages in blood vessels and reduced oxygen delivery to tissues. Individuals who are homozygous recessive (HbSS) experience symptoms such as pain crises, anemia, and increased risk of infections.

• Evolution: Key concepts including natural selection and common descent with modification.

  • Natural Selection: The process by which organisms better adapted to their environment tend to survive and produce more offspring. This results in the gradual adaptation of species to their environment over time.

  • Common Descent: The scientific theory that all species share a common ancestor and evolve over time through a branching process. This theory posits that species diverged from common ancestors, leading to the rich diversity of life we see today. Modifications occur through genetic variation and natural selection; favorable traits are passed on to subsequent generations while unfavorable traits may diminish, contributing to the evolution of species over time.

• Germ Theory: Principles and significance in understanding diseases. Germ theory states that many diseases are caused by microorganisms, specifically pathogens such as bacteria and viruses. This understanding has led to advancements in hygiene, sanitation, and the development of antibiotics, significantly improving public health and disease prevention. It emphasizes the importance of microbiology in disease etiology.

Biological Concepts

• Atomic Structure: Understanding the basic atomic structure is crucial as it underpins all biological molecules and interactions. Each atom consists of protons, neutrons, and electrons.

  • Protons: Positively charged particles found in the nucleus of an atom. The number of protons determines the element's identity.

  • Neutrons: Neutral particles also located in the nucleus, contributing to atomic mass but not charge.

  • Electrons: Negatively charged particles that orbit the nucleus, playing a key role in chemical bonding and reactions.

• Enzymes: Biological catalysts that speed up chemical reactions in the body by lowering activation energy, which allows metabolic processes and biochemical reactions to occur efficiently under physiological conditions. Enzymes are highly specific, meaning each enzyme usually catalyzes only one type of reaction.

• Viruses: Infectious agents that are much smaller than bacteria and can only replicate inside a host cell. Certain viruses, like Human Papillomavirus (HPV) and Hepatitis B virus, can integrate into host DNA and promote uncontrolled cell growth, leading to cancer. HPV, for example, is strongly linked to cervical cancer, while Hepatitis B is associated with liver cancer. Viruses lack cellular structure and must hijack living cells to reproduce, making them significant in discussing viral oncogenesis.

• Macromolecules: Large complex molecules made from smaller subunits called monomers. The main types are:

  • Carbohydrates: Energy sources and structural components composed of carbon, hydrogen, and oxygen. Simple carbohydrates (sugars) provide quick energy, while complex carbohydrates (starches, fiber) serve as longer-term energy sources and play crucial roles in maintaining homeostasis. They are essential in cellular respiration and are involved in cell signaling and structure.

  • Proteins: Made of amino acids, they perform a vast array of functions including catalyzing reactions, providing structure, and facilitating communication within and between cells.

  • Lipids: Include fats and oils, primarily serving as energy storage and components of cell membranes.

  • Nucleic Acids: DNA and RNA, responsible for storing and transmitting genetic information.

• Difference Between DNA and RNA:

  • Structure: DNA (deoxyribonucleic acid) is typically double-stranded, forming a double helix, whereas RNA (ribonucleic acid) is usually single-stranded.

  • Sugar Component: The sugar in DNA is deoxyribose, while the sugar in RNA is ribose. The difference in the sugar structure impacts stability and function.

  • Nitrogenous Bases: DNA contains the bases adenine (A), guanine (G), cytosine (C), and thymine (T), while RNA contains adenine, guanine, cytosine, and uracil (U), which replaces thymine in RNA.

  • Function: DNA stores genetic information that is inherited, while RNA plays a key role in translating that genetic information into proteins. Different types of RNA (mRNA, tRNA, and rRNA) serve distinct functions in the protein synthesis process, including messenger RNA (mRNA) which carries the code from DNA to the ribosome, transfer RNA (tRNA) which brings amino acids to the ribosomes, and ribosomal RNA (rRNA) which makes up the core of ribosome's structure and catalyzes protein synthesis.

• Reproductive Strategies: Differences between asexual and sexual reproduction, including the advantages and disadvantages of each.

  • Asexual Reproduction: Involves a single organism producing offspring genetically identical to itself (clones), allowing rapid population growth. Advantages include quick reproduction and no need for a mate.

  • Sexual Reproduction: Involves the fusion of male and female gametes, resulting in genetic diversity among offspring, which is beneficial for adaptation and survival in changing environments.

• Role of the SRY gene: The SRY gene, located on the Y chromosome, triggers male sex determination in embryos. Its activation leads to the development of male reproductive structures and influences the production of male sex hormones.

Scientific Principles

• Scientific Method: Steps in conducting scientific research include observation, hypothesis formulation, experimentation, and conclusion drawing. Each step is vital in the process as follows:

  1. Observation: This involves identifying a phenomenon to study and gathering information about it.

  2. Hypothesis Formation: Formulating a testable prediction based on observations. A well-defined hypothesis provides a clear direction for the research.

  3. Experimentation: Conducting controlled experiments to test the hypothesis. It’s crucial to carefully plan and execute experiments, ensuring all variables are adequately controlled. This step may also include peer review for additional scrutiny.

  4. Data Collection and Analysis: Gathering data from the experiments and analyzing it to determine whether it supports or refutes the hypothesis.

  5. Conclusion Drawing: Based on the analysis, conclusions are drawn. It is critical to revisit the experimental procedures and double-check results to ensure reliability and repeatability. Discrepancies or unexpected outcomes should be investigated further, often leading to refined hypotheses and additional experimentation.

  6. Communication: Finally, results should be communicated to the scientific community for validation and further research, which emphasizes transparency and collaboration in science.

Genetics

• Cell Cycle: Phases of the cell cycle and significance, including interphase (G1, S, G2) and mitotic phase (mitosis and cytokinesis).

  • Interphase: The phase where the cell spends most of its life, consisting of three sub-phases:

    • G1 Phase (Gap 1): The cell grows in size, synthesizes mRNA and proteins, and prepares for DNA replication. The cell also goes through a checkpoint to assess if it is ready to move on to the synthesis phase.

    • S Phase (Synthesis): The cell replicates its DNA, doubling the genetic material so that each daughter cell will have a complete set of chromosomes. This is critical for cell division.

    • G2 Phase (Gap 2): The cell continues to grow and produce proteins necessary for mitosis. It also undergoes another checkpoint to ensure that DNA has been replicated accurately and is undamaged. The cell prepares for mitosis by synthesizing microtubules that will be used to pull apart the duplicated chromosomes.

  • Mitotic Phase (M Phase): The phase where the cell divides its copied DNA and cytoplasm to form two new cells. This phase includes mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis, which physically separates the two daughter cells.

• Oncogenes & Proto-Oncogenes: Understanding mutations and their roles in cancer development. Proto-oncogenes are normal genes that can become oncogenes due to mutations that lead to uncontrolled cell division and cancer. Risk factors that can contribute to the development of cancer include genetic predispositions, environmental exposures like chemicals or radiation, and lifestyle choices such as smoking and diet.

• Genetic Variations: Definition of epistasis (interaction between genes where one gene can mask the effect of another) and pleiotropy (one gene influences multiple traits). Examples include:

  • Risk associations with certain genes, such as links to breast cancer in women (e.g., BRCA1 and BRCA2 mutations), which can lead to higher incidences of breast and ovarian cancers.

• Eukaryotes vs. Prokaryotes: Key differences in cell structure. Eukaryotic cells contain organelles (e.g., nucleus, mitochondria) and have linear DNA, while prokaryotic cells lack organelles and generally possess circular DNA, representing a more simplistic cellular structure.

• Nucleotides: The basic building blocks of nucleic acids (DNA and RNA). Nucleotides consist of a sugar, a phosphate group, and a nitrogenous base. The primary bases are adenine, cytosine, guanine, and thymine for DNA, and uracil replaces thymine in RNA. They pair up to form the genetic code in nucleic acid structures.

• Alleles: Define what an allele is. An allele is a variant form of a gene that occurs at a specific locus on a chromosome. Each individual inherits two alleles for each gene, one from each parent. This combination of alleles determines the genotype (the genetic constitution) and can influence the phenotype (the displayed traits) of an organism. Alleles can be dominant or recessive, where a dominant allele will manifest in the phenotype even in the presence of a different allele, while a recessive allele will only manifest when both alleles for that trait are recessive.

• Polymers vs Monomers: Polymers are large molecules composed of repeating structural units (monomers), connected by covalent bonds. (e.g., proteins are polymers made of amino acid monomers, and nucleic acids are polymers of nucleotide monomers).

• Dominant vs. Recessive Alleles:

  • Dominant Alleles: Alleles that express their trait even when one copy is present (e.g., Aa or AA).

  • Recessive Alleles: Alleles that require two copies to express their trait (e.g., aa). An example of a dominant trait is brown eyes (B), while blue eyes (b) are typically recessive. In a Punnett Square, the combination of alleles determines the probability of offspring expressing a trait. Individuals with one dominant and one recessive allele may show the dominant trait (heterozygous), while those with two recessive alleles will display the recessive trait (homozygous recessive).

Laboratory Content for Midterm Exam

• Microscope Parts: Key components include:

  • Objective: The lens closest to the specimen; different objectives provide varying levels of magnification.

  • Stage: The platform where the slides are placed for viewing.

  • Coarse Adjustment Knob: Used for quick focusing of the microscope, moving the stage up and down.

  • Fine Adjustment Knob: Allows for small adjustments to focus the image clearly.

  • Oculars: Eyepieces through which the specimen is viewed, usually providing 10x magnification.

  • Iris Condenser: Regulates the amount of light that reaches the specimen, enhancing image clarity.

• Metric Conversions: Understand conversion factors:

  • Meters to centimeters (M → cm)

  • Meters to millimeters (M → mm)

  • Grams to milligrams (G → mg)

  • Kilograms to grams (Kg → g)

  • Degrees Fahrenheit to Celsius (°F – °C)

  • Microliters to milliliters (μL → mL).

• Experimental Controls: Importance of a placebo as a control to account for psychological factors in experiments, ensuring that results are due to the treatment rather than participant expectations.

• Genetics Terms: Heterozygous vs. homozygous (dominant/recessive).

  • Heterozygous: An organism with two different alleles for a trait (e.g., Aa).

  • Homozygous: An organism with two identical alleles for a trait (e.g., AA or aa).

• Key concepts: Chromosomes (structures that carry genetic information), genotype (the genetic makeup of an individual), phenotype (observable traits), and alleles (variations of a gene).

• Punnett Square: A diagram used to predict genetic variations in offspring from parental gene combinations.

• Mendel's Experiments: Overview of his work with pea plants, showcasing how traits are inherited through dominant and recessive relationships in human traits.