Biology Chapter on DNA and Protein Synthesis

Introduction to Life Science: Methodology - Scientific Method

• The scientific method is a process used to acquire scientific information.
• The scientific method involves a series of steps.
• The steps of the scientific method are: Observation, Problem, Hypothesis, Experiment, Data, Conclusions.

Observation

• Observation gathers information and studies previous data.
• Scientists use all their senses (sight, smell, taste, touch, sound) to make observations.
• Scientists also use instruments like microscopes and utilize the past work of other scientists to make observations.
• Observations lead to questions.
• Valid questions are those that can be answered by experimentation.

Problem

• Observations lead to questions.
• Scientists only consider questions that can be answered through experimentation.
• Moral and religious beliefs aren't appropriate considerations for scientific questions because they can't be tested scientifically.
• The question should be one that asks directly how one variable affects another variable.

Hypothesis

• A hypothesis is a testable statement that predicts how one variable will affect another variable based on information from various sources.
• The hypothesis is usually expressed as an "if...then..." statement.
• A hypothesis should be stated in a way that can be easily measured and used to answer the original problem/question.

Experiment

• Testing a hypothesis involves conducting an experiment or further observations.
• The experiment should have a control group, which follows all steps but not the variable being tested.
• Controlled variables, also called control groups, must remain constant.

Data

• Data is the results of an experiment.
• Data should be observable and objective rather than subjective or based on opinion.
• Mathematical data is often displayed in a graph or table.
• The larger the sample size, the more statistically significant the result is.

Conclusions

• Scientists analyze data to form conclusions.
• The conclusion states whether the results of the experiment support or reject the hypothesis.
• Experiments and observations must be repeatable (get the same results).

Variables

• A variable is a factor, trait, or condition.
• Variables:
  • Independent variable: The variable being tested, can be manipulated by a scientist.
  • Dependent variable: The variable that changes in response to the independent variable, also called the response variable.
  • Controlled variables: Variables that have to be kept constant during testing to test the relationship between the independent and the dependent variables. 

Scientific Theories

• The ultimate goal of science is to understand the natural world in terms of scientific theories.
• Scientific theories join hypotheses; supported by a range of experiments, observations and data.

Basic Theories of Biology

• Cell Theory: All organisms are composed of cells, and new cells only come from pre-existing cells.
• Homeostasis: The internal environment of an organism stays relatively constant within a range that is protective of life.
• Gene Theory: Organisms contain coded information that dictates their form, function, and behavior.
• Ecosystem: Organisms are members of populations, which interact with each other and with the physical environment within a particular locale.
• Evolution: A change in the frequency of traits that affect reproductive success in a population or species across generations.

Fundamentals of Life: Continuity of Life - Protein Synthesis

• Protein synthesis is the process of using the information within a gene to synthesize a protein.
• Protein synthesis involves the participation of mRNA, rRNA, and tRNA.
• Protein synthesis includes Transcription and Translation.

Transcription

• During transcription, a portion of DNA serves as a template for mRNA formation.

Translation

• During translation, mRNA determines the sequence of amino acids in a polypeptide.
• Proteins differ from one another by the sequence of their amino acids.
• Proteins determine the structure and function of cells and the physical shape of the organism.

Fundamentals of Life: Continuity of Life - DNA Replication

• DNA replication takes place before cell division.
• It is the copying of one DNA molecule into two identical molecules.
• Each original strand serves as a template for the formation of DNA strands.
• DNA replication is considered semiconservative. 
• DNA base pairs are: Adenine (A) to Thymine (T), and Cytosine (C) to Guanine (G).

The Cell Cycle

• The cell cycle is the life cycle of a cell.
• The stages for the cell cycle are:
  • Interphase (G1,S, G2) - G1 Phase: Cell grows, copies organelles and makes molecular building blocks. - Synthesis (S) Phase: DNA Replication happens. - G2 Phase: Cell continues to grow, makes proteins and organelles needed for Mitosis.
  • M Phase (Mitosis): The cell separates its DNA into two sets and divides its cytoplasm forming two daughter new cells. - Mitosis - Nuclear Division - Cytokinesis - Cytoplasm Division

DNA Replication The Steps

• The two strands of DNA are hydrogen-bonded together.
• A dividing cell must first duplicate its genome (which may consist of one or more chromosomes).
• The enzyme DNA helicase unwinds and "unzips" the double-stranded DNA. 
• New complementary DNA nucleotides fit into place along divided strands by base pairing. These nucleotides are joined together by DNA polymerase. 
• DNA ligase repairs any breaks in the sugar-phosphate backbone.
• Enzymes repair damaged DNA and fix mistakes during DNA replication.

Mitosis

• Mitosis is the cell division in which the chromosome number stays constant (46 chromosomes becoming 46 chromosomes).
• DNA replication produces duplicated chromosomes with two sister chromatics held together by a centromere.

Meiosis

• Meiosis is a process of cell division that results in four genetically different haploid cells.
• Meiosis has two divisions: Meiosis I and Meiosis II.

Mitosis vs Meiosis

• Mitosis is a process of cell division used for growth and repair in the body.
• Meiosis is used to produce gametes for sexual reproduction.
• Major differences in Mitosis vs. Meiosis occur in the two divisions and the separation of chromatids. Crossing-over occurs in Meiosis, and the resulting cells in meiosis are genetically unique. 

Human Life Cycle

• Human life requires both mitosis and meiosis.
• Meiosis in females is called oogenesis.
• Meiosis in males is called spermatogenesis. 

Cell Transport

• Cell transport is the movement of substances across the cell membrane.
• Passive transport: Substances move from a high concentration to a low concentration (across a concentration gradient). No energy is required.
  • Diffusion
  • Osmosis
  • Facilitated diffusion
• Active transport: Substances move from a low concentration to a high concentration (against a concentration gradient). Energy is required.
  • Active transport (protein carrier)
  • Endocytosis
  • Exocytosis

Cell Organelles

• Structure: plasma membrane - protein-attached phospholipid bilayer
• Function: regulates passage of substances in and out of the cell, semipermeable membrane
• Structure: Nucleus, nucleolus- contains DNA, genetic material of the cell
• Function: stores genetic material of the cell
• Structure: Ribosomes- two subunits
• Function: carry out protein synthesis
• Structure: Endoplasmic reticulum (smooth, rough)- flattened vesicles
• Function: smooth: creates phospholipids, rough: creates proteins
• Structure: Golgi apparatus- slightly curved sacs
• Function: Collects, sorts, packages, and distributes proteins and lipids.
• Structure: Vesicles- membrane bound organelles
• Function: transport of materials outside or inside of cells.
• Structure: Lysosomes- membrane-bound vesicles 
• Function: contain digestive enzymes, break down unwanted substances, worn-out part of the cell.
• Structure: Vacuoles- membranous sacs.
• Function: store substances like water, pigments, and toxins.
• Structure: Chloroplasts, 
• Function: Chlorophyll, for photosynthesis, provide carbohydrates to mitochondria
• Structure: Mitochondria
• Function: Cellular respiration

Prokaryotes vs Eukaryotes

• Similarities; both have a cell membrane, cytoplasm and ribosomes
• Differences; Eukaryotes have a true nucleus with membrane bound organelles, prokaryotes do not have a nucleus or membrane bound organelles.

Cell Metabolism and Photosynthesis

• Chloroplasts; site of photosynthesis
• Photosynthesis converts solar energy into chemical energy.
• The reactants for Photosynthesis are water and carbon dioxide.
• The product for Photosynthesis is glucose. 
• Cell respiration converts chemical energy into cellular energy (in the form of ATP) for basic cell processes.
• Reactants for cellular respiration: Glucose
  • Products for cellular respiration: Carbon dioxide, Oxygen.

Cellular Respiration & Fermentation

• Breakdown of glucose is called cellular respiration and produces ATP. 
• Anaerobic respiration:
  • Happens without sufficient oxygen (O2).
  • Animal cells produce lactic acid.
  • Plant cells produce ethanol.
• Aerobic respiration:
  • Requires Oxygen to fully break down glucose and create much more ATP. 

Karyograms

• Karyograms show the chromosomes of an organism in a visual display.
• They are used for genetic diagnoses to detect changes in chromosome number. (i.e. Down Syndrome, Turner Syndrome, Klinefelter Syndrome).
• The process of karyograms:
  • Cells are arrested in metaphase.
  • Specific techniques (e.g., Amniocentesis, Chorionic Villi Sampling) are used to acquire the cells needed. 

The Importance of Nucleic Acids: Introduction to Nucleic Acids

Nucleic Acids are vital molecules made of monomers called nucleotides used for carrying and storing genetic information that enables living organisms to reproduce their complex components.

• There are two main classes of nucleic acids
  • DNA (deoxyribonucleic acid) - stores information
  • RNA (ribonucleic acid) - protein synthesis (works with DNA)
• DNA is a double-stranded helix; structured from nitrogen bases, sugar, phosphate.
• RNA is a single-stranded structure that has a similar structure to DNA with an exception of Thymine to Uracil.
• ATP (adenosine triphosphate) is a modified nucleotide structure that carries and transfers energy within cells.

Evolution

• Evolution is the process by which a species changes through time.
• There are two major aspects:
  • Descent from a common ancestor: Explains the common chemistry and cell structure of all living things.
  • Adaptation to the environment: Adaptations make an organism more able to survive and reproduce.

Natural Selection

• Natural Selection: The process driving evolution which is the process by which organisms with favorable traits tend to leave more offspring than their peers, thus passing on their genetic traits that led their favorable outcome to the next generation.
• Key factors in natural selection are:
  • Variation: Individuals within populations differ in physical characteristics.
  • Competition: Individuals compete for limited resources.
  • Adaptation: Favorable traits help individuals survive and reproduce. 
  • Fitness: A measurement of how well an organism survives and reproduces.

The Origin of Life

• The Cell Theory states that all living things are made of cells, with pre-existing cells and that all cells are formed from pre-existing cells. All cells have the ability to reproduce and pass on genetic information to the next generation.
• The Chemical Theory states that chemical evolution produced the first cells from non-living chemicals in the early days on Earth.
• The Miller-Urey experiment simulated conditions on early Earth to demonstrate that organic molecules could be created from inorganic molecules. The hypothesis for the chemical evolution of the first cells was shown through the experiment where inorganic molecules converted into organic molecules with energy.
• Endosymbiotic Theory; explains that eukaryotic cells evolved from prokaryotic cells.  

This quiz covers key concepts from biology related to DNA replication, RNA transcription, and protein synthesis. It includes questions on the enzymes involved, types of RNA, and the structural aspects of fatty acids and proteins. Test your understanding of these fundamental biological processes and their significance in cellular functions.