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Unit 1: The Science of Biology • Q1: Define Biology • A1: Biology is the study of living things • Q2: List and describe the 5 major steps of the scientific method • A2: Although the exact number of steps may vary, the process of science should follow the same basic steps of the scientific method: – State the problem or question – Make observations and/or gather information (research) – Make a HYPOTHESIS – based on your observations/research, make a prediction of what you think will happen – Design and conduct a controlled experiment – Analyze data and draw a conclusion – determine WHY the results of the experiment occurred and communicate your findings Unit 1: The Science of Biology • Q3: Compare and contrast the terms independent and dependent variable and give an example of each • A3: Independent variable is the condition of the experiment that the scientist chooses to change or do differently, while the dependent variable is whatever is measured, observed, or recorded. – For example, if I do an experiment to test the effects of various types of fertilizer on the height of plants, the TYPE OF fertilizer is the independent variable, while the height of the plants is the dependent variable Unit 1: The Science of Biology • Q4: What is a control, and what is its purpose in the experiment? • A4: The control (or CONTROL GROUP) is the part of the experiment that you do NOT test. In other words, it is the thing that you leave alone. For example, in the experiment described in Q3, the control group would be a group of plants that received NO fertilizer. It is needed so that I can compare my results to what is “normal.” Unit 1: The Science of Biology • Q5: List and describe the 5 characteristics of a living thing • A5: Although the number of characteristics can vary, all living organisms have the following basic characteristics: – Organization: All organisms are made of one or more cells, and each of these cells contains DNA – Reproduction: All living things can make more living things of the same species – Growth & Development: All living things increase in size/mass and change over time – Maintenance of Homeostasis: All living things use energy (metabolism) and respond to stimuli in their environment to maintain stable internal conditions – Adaptations formed through Evolution: All living things have inherited characteristics and/or behaviors that help them survive in their environment Unit 1: The Science of Biology • Q6: Define SCIENTIFIC THEORY • A6: A scientific theory is an explanation of the natural world that is based on evidence, observations, and experimental data. It is a logical explanation of how something works, for which all the current evidence and research says it is correct. REMEMBER, in science, a theory is NOT “just a theory”! Unit 2: Ecology • Q7: Define ECOLOGY • A7: Ecology is the scientific study of the interrelationships between organisms and their environment • Q8: Distinguish between populations, communities, ecosystems, biomes, and biosphere • A8: (See Figure) Unit 2: Ecology • Q9: Draw and interpret food chains and food webs • A9: A food chain is a simple diagram of one set of feeding relationships in an ecosystem, while a food web is a more complex diagram, showing ALL of the feeding relationships in an ecosystem Unit 2: Ecology • Q10: Draw and interpret energy pyramids based upon mass • A10: The amount of energy that flows through can ecosystem can be measured using the BIOMASS of the organisms in the food chain. The biomass is the mass (or weight) of living material in each trophic level. Only 10% of the biomass is transferred from one trophic level to the next (10% RULE) Unit 2: Ecology • Q11: Identify the various TROPHIC LEVELS • A11: A trophic level refers to a “feeding level” in a food chain. Producers (autotrophs) make up the 1st trophic level, followed by primary consumers (heterotrophs), secondary consumers, and top (tertiary) consumers Unit 2: Ecology • Q12: Follow the energy transfers through ecosystems • A12: THE 10% RULE says that only 10% of the energy that is captured in the first trophic level (plants) is passed on to the next trophic level. The other 90% of the energy is used up by the organism for its own metabolism, or given off as heat Unit 2: Ecology • Q13: Differentiate between biotic and abiotic factors in various ecosystems/biomes • A13: Biotic factors are the LIVING things in the environment, while abiotic factors are the NONLIVING thing in the environment. – For this question, be sure to know how these factors differ in the different biomes (tundra, taiga, deciduous forest, desert, grassland, tropical rain forest)! Unit 3: Biochemistry • Q14: List the 3 parts of an atom and give their charge • A14: An atom contains protons (positive charge), neutrons (no charge), and electrons (negative charge) • Q15: Define the following terms and give an example – element, compound • A15: An element is a substance made of only one type of atom that cannot be broken down into any simpler substance, such as carbon. A compound is a substance made of molecules, consisting of 2 or more kinds of atoms, such as water Unit 3: Biochemistry • Q16: Define the term ion. How are they formed? • A16: An ION is an atom that has an overall positive or negative charge because it has gained or lost electrons • Q17: Compare and contrast ionic and covalent bonding. Which one is stronger? • A18: A covalent bond is formed when atoms share electrons (such as in water molecules), while an ionic bond is formed when atoms gain or lose electrons, and are then attracted because of opposite charges. Ionic bonds are stronger Unit 3: Biochemistry • Q18: List 3 properties of water that make it special • A18: Water has the following properties (be sure that you know what each of these means!) – High heat of vaporization – Capillary action – Surface tension – Expands when frozen – Universal solvent Unit 3: Biochemistry • Q19: Define polarity • A19: Polarity occurs when a molecule (such as water) has a slight positive charge on one end and a slight negative charge on the other end. This causes the polar molecules to attract • Q20: Define the following terms and describe how they relate to each other: solution, solute, and solvent • A20: A solution is a mixture formed when one substance is evenly dissolved in another substance, such as salt water. The substance that is dissolved is the solvent (salt), while the solvent is the substance doing the dissolving (water) Unit 3: Biochemistry • Q21: Define pH. Compare/contrast acids & bases • A21: The pH of a substance is a measure of the concentration of Hydrogen ions dissolved in the substance. It is essentially a measure of how acidic or basic a substance is. The pH scale goes from 0-14. Anything with a pH below 7 is an ACID; anything with a pH above 7 is a BASE. Substances with a ph of 7 are NEUTRAL. Unit 3: Biochemistry • Q22: Define monomer & polymer • A22: A POLYMER is a large molecule made up of many smaller molecules or subunits. The smaller molecule or subunit is the MONOMER • Q23: List the 4 macromolecules. Give a function for each. Describe what each one is made up of. • A23: Polymer Monomer Function (Macromolecule) Carbohydrate Glucose Used for quick energy Lipids Fatty Acids Used for energy storage & insulation Proteins Amino Acids Enzymes & building structures Nucleic Acids Nucleotides DNA & RNA Unit 3: Biochemistry • Q24: Define chemical reaction. List the parts of a chemical reaction and give example. • A24: A chemical reaction is process in which chemical bonds are formed or broken. The REACTANTS are what goes into a reaction; the PRODUCTS are what is made from a reaction • In the photosynthesis reaction below, the reactants are water and carbon dioxide, while the products are glucose and oxygen Unit 3: Biochemistry • Q25: Compare and contrast exothermic and endothermic reactions • A25: Exothermic reactions are chemical reactions in which energy is released or given off (chemical bonds are broken), while endothermic reactions are chemical reactions in which energy must be put into the reaction (chemical bonds are formed) • Q26: Explain what activation energy is and how is it used • A26: Activation energy is the initial energy needed to start a chemical reaction, similar to the “spark” needed to ignite a fire Unit 3: Biochemistry • Q27 & Q28: Define catalyst. How are they used in reactions? Why are enzymes called biological catalysts? • A27 & A28: A CATALYST is anything that speeds up a chemical reaction, but is not used up in the reaction. ENZYMES are a special type of protein that act as a biological catalyst. They help to start and/or speed up reactions in living things. Unit 3: Biochemistry • Q29: Explain the enzyme substrate complex and how it works. Why is it compared to a lock and key model? • A29: An enzyme bonds to a specific molecule (the substrate) at a specific location on the molecule (known as the active site). The enzyme and substrate molecules fit together like a lock and key. Once bonded together, the enzyme helps to break down the substrate into the products. Unit 4: Cells • Q30: State the 3 parts of the cell theory. • A30: The Cell Theory states that: – All cells must come from preexisting cells – The cell is the basic unit of structure and function in all organisms – All organisms are made of one or more cells Unit 4: Cells • Q31: Give the contributions of the following scientists to the cell theory: Hooke, Leewenhoek, Schleiden, Schwann and Virchow. • A31: Cell Scientists – Robert Hooke – examined cork cells; first to use the word “cell” – Anton van Leewenhoek – first to see living cells; developed early microscope – Schleiden – Examine plant cells; stated that all plants are made of cells – Schwann – Examined animal cells; stated that all animals are made of cells – Rudolf Virchow – 1st to see the nucleus and its role in cell reproduction; concluded that all cells must come from pre-existing cells Unit 4: Cells • Q32: Compare and contrast eukaryotic & prokaryotic cells • A32: Prokaryotes are BACTERIA only – they are small, simple cells with NO ORGANELLES and NO NUCLEUS. Eukaryotes are everything else except for bacteria (plants, animals, etc.). The cells are larger and more complex, and contain a nucleus and other organelles. • Q33: Define the term organelle and give the function of each of the following organelles: • A33: Please see the chart on page 199 of “zebra book”, or follow the link below: • http://www.biologyjunction.com/cell_functions.htm Unit 4: Cells • Q34: Compare and contrast plant and animal cells. • A34: Plant cells have a cell wall and chloroplasts. Their cell wall gives them more of a rectangular shape, and they are often larger. Animal cells have centrioles, are more round in shape, and they are typically smaller • Q35: List the parts of the cell membrane and their functions. • A35: The cell membrane consists of 2 layers of phospholipids, proteins, carbohydrates and cholesterol Unit 4: Cells • Q36: Give the name of the current accepted model of the cell membrane. • A36: The currently accepted model of the Cell Membrane is known as the Fluid Mosaic Model. It is referred to as “fluid” because it is flexible, and a “mosaic” because it is made of many different pieces (molecules) • Q37: Compare active and passive transport including: diffusion, osmosis, facilitative diffusion, endocytosis and exocytosis. • A37: Passive transport does NOT require energy because the molecules are moving from an area of high concentration to low concentration. Diffusion, osmosis, and facilitated diffusion are types of passive transport. Active transport does require energy because the molecules are moving from low to high concentration. Endocytosis and exocytosis are types of active transport Unit 4: Cells • Q38: Describe what happens to a cell in each of the following solutions: hypotonic, isotonic and hypertonic. Draw an example of each • A38: – Isotonic – concentration of water and solutes is equal inside and outside of the cell; the cell has no net movement of water – Hypertonic – The concentration of water inside the cell is HIGHER than the concentration of water outside of the cell. Water will move OUT of the cell – Hypotonic – The concentration of water inside the cell is LOWER than the concentration of water outside of the cell. Water will move into the cell. Unit 5: Cellular Reproduction • Q39-Q41: List and describe each of the major phases of the cell cycle. Explain the 3 steps of interphase. Explain the 4 steps of Mitosis. • A39-41: The Cell Cycle is the life cycle of the cell. It consists of 3 main phases: Interphase, the time when a cell is not dividing, but is doing all other metabolic activities; mitosis, the process of cell division; and Cytokinesis, the brief phase when the 2 newly formed cells are cut apart. • Interphase consists of 3 “sub-phases: G1 Phase (the 1st growth phase), S Phase (when the cell is SYNTHESIZING new DNA), and G2 Phase (the 2nd growth phase). • Mitosis consists of 4 phases: – Prophase: when the cell PREPARES to divide – Metaphase: when the chromosomes line up in the MIDDLE of the cell – Anaphase: when the sister chromatids are pulled APART – Telophase: when the TWO new cells begin to form Unit 5: Cellular Reproduction • Q42: Give 3 reasons that cells are limited on how large they can grow before they must divide. • A42: Cells must remain small because of 3 factors: – Surface-Area-to-Volume: as a cell’s size increases, its volume increases at a much faster rate than its surface are, and the cell membrane cannot move molecule in and our quickly enough to maintain homeostasis – DNA: The DNA works like a set of instructions in the nucleus; if the cell becomes too large, the DNA cannot control all of the cell’s activities – Diffusion: Diffusion is a SLOW process, so if the cell is large, molecules cannot diffuse fast enough through the cell to maintain homeostasis Unit 5: Cellular Reproduction • Q43: Define the follow terms and explain how they are related to one another: chromosome, chromatin. • A43: Chromatin and chromosomes are both DNA, just in different forms. Normally, DNA is uncoiled in the nucleus. This “relaxed” form of DNA is CHROMATIN. When a cell prepares to divide in Prophase, the DNA coils up very tightly. This tightly coiled DNA is a CHROMSOME • Q44:Name the 2 factors that regulate the cell cycle. • A44: The cell cycle is regulated primarily by ENZYMES. These enzymes (known as cyclindependent kinases) monitor the cell cycle and trigger the process of cell division. These enzymes bind to specialized proteins called CYCLINS to control cell division Unit 5: Cellular Reproduction • Q45: What happens when the cell cycle grows out of control? • A45: When a cell grows out of control, this abnormal cell growth can potentially lead to the growth of a cancerous tumor • Q46: What are stem cells? How are stems cells beneficial in research? • A46: Stem cells are cells that are undifferentiated, meaning they have not yet started to develop into a specific type of cell. Stem cells are particularly promising for researchers because they could be used to generate any type of cell, which could then be used to treat an injury (like a spinal cord injury) or cure a disease (such as Sickle Cell Anemia) • Q47: Name the levels of organization within an organism( start with cells and build up) • A 47: Cells Tissues Organs Organ Systems Organism Unit 5: Cellular Reproduction • Q48: What is the difference between gametes and somatic cells? • A48: Somatic cells are “regular” body cells, such as skin, bone, or muscle cells. Somatic cells are made through MITOSIS. Gametes are reproductive cells: sperm or egg cells. These cells are made through MEIOSIS, so they contain HALF the number of chromosomes (haploid) • Q49: What is the difference between autosomes and sex chromosomes? Which numbered pairs in humans are autosomes? Which pair are sex chromosomes? • A49: Autosomes are “regular” chromosomes. In humans, the autosomes are pairs 1-22. Sex chromosomes are the pair of chromosomes that differ in males and females. In humans, this is pair 23. Females have 2 X-chromosomes, and males have 1 X-chromosome and 1 Y-chromosome. • Q50: Define sexual reproduction and give it’s advantages. • A50: Sexual reproduction involves the exchange of genetic material between 2 organisms. The resulting offspring are genetically different from the parents. Sexual reproduction gives an advantage to the species because it provides GENETIC VARIATION. This diversity make the species less susceptible to disease, and allows the species to become better adapted to its environment. Unit 5: Cellular Reproduction • Q51: Explain the process of meiosis. Explain each step of meiosis. How many cells do you start with? Are they diploid or haploid? How many daughter cells do you end with? Are they haploid or diploid? • A51: Meiosis is the process that produces gametes (reproductive cells). It involves TWO cell divisions. The end result is 4 genetically different HAPLOID gamete cells. Unit 6: Cellular Energy • Q1: Explain the difference between ATP & ADP molecules. • A1: ATP (Adenosine Triphosphate) is the molecule that all cells use for energy (it is like your cell’s fuel). Energy is stored in the bonds between the 3 phosphates of this molecule. When a cell needs to release this stored energy, a phosphate is broken off to produce ADP (Adenosine Diphosphate), a molecule with just 2 phosphates. Unit 6: Cellular Energy • Q2-Q3: Explain the process of photosynthesis and include the following information: organelle where it takes place, the 2 major reactions and their locations within the organelle and the overall chemical reaction of photosynthesis. (know what goes in, what comes out). What is the role of chlorophyll in the photosynthetic reaction? • A2-A3: Photosynthesis has two major steps, which take place in the cholorplast. Step one is the Light-dependent reactions. Sunlight is absorbed by the chlorophyll, and this energy is used to split a water molecule. ATP and NADPH (another energy storing molecule) are produced and sent to the 2nd step. The 2nd step is the Light-Independent reactions. The products of the first step are used, and carbon dioxide is take in. As a result, sugars (glucose) are produced. Unit 6: Cellular Energy • Q4-Q5: Explain the process of glycolysis including: where it takes place, what it produces and if it requires oxygen. Explain the process of cellular respiration include the following information: organelle where it takes place, the 2 major reactions and their locations within organelle, and the overall chemical reaction of cellular respiration. • A4-A5: Cellular Respiration is the process that breaks down the glucose in your food to make ATP (energy). Glycolysis is the 1st step of cellular respiration. It occurs in the mitochondria and does NOT require oxygen (anaerobic). Glucose is broken down to produce ATP and NADH (an energy-carrying molecule). After glycolysis, the 2nd and 3rd steps of cellular respiration happen in the mitochondria. The products of glycolysis are sent to the mitochondria for the 2nd step, which is Krebs Cycle (or Citric Acid Cycle). The 3rd step is the Electron Transport Chain. This last step is the most important step because it produces approximately 32 ATP. Unit 6: Cellular Energy • Q6: Explain the 2 different types of fermentation and where they take place. Do they require oxygen? • A6: Fermentation is ANAEROBIC respiration, meaning they do not require oxygen. They each break down glucose to make 2 ATP molecules. – Lactic Acid Fermentation – occurs in your muscle cells when oxygen is not available; glucose is broken down to produce 2 ATP and lactic acid as a waste product (which causes muscle soreness) – Alcoholic Fermentation – used by bacteria or yeast; glucose is broken down to make 2 ATP, carbon dioxide, and ethyl alcohol. Unit 6: Cellular Energy • Q7: Explain how photosynthesis and cellular respiration are related, (why one must rely on the other to exist). • A7: Photosynthesis uses carbon dioxide and water (and sunlight) to make glucose and oxygen. Respiration uses what photosynthesis makes (glucose and oxygen) to produce what photosynthesis needs (carbon dioxide and water). They are essentially opposite reactions; the products of one are the reactants of the other. Unit 7: Genetics • Q8: Define the following terms: – – – – – – – – – – – Genetics – The science of heredity traits – an inherited characteristic Heredity – the study of how traits are inherited over time Gene – a section of DNA that controls a trait allele – A form of a gene homozygous – when an organism has 2 of the SAME allele heterozygous - when an organism has 2 DIFFERENT alleles Genome – the entire collection of genes in an organism Genotype – the combination of genes and organism has phenotype – the actual physical appearance or trait Dominant – the “stronger” trait that hides or masks the other trait – recessive – the “weaker” trait that is hidden by the other trait Unit 7: Genetics • Q9:What is Mendel’s contribution to genetics? • A9: Gregor Mendel was an Austrian monk who used pea plants to study heredity in the 1860’s. He is referred to as the Father of Genetics because he developed important laws of heredity – Law of Independent Assortment – The genes for each trait separate independently from one another – Law of Segregation – During Meiosis, the two alleles for each trait separate, so that each parent passes on only one allele for each trait – Rule of Dominance – If an organism inherits both the dominant allele and the recessive allele, the dominant trait is shown Unit 7: Genetics • Q10: In the following problem, identify the genotype and phenotype of the offspring. A red flower is crossed with a blue flower. Red is dominant to blue. The red flower is heterozygous and the blue flower is homozygous. Draw a punnett square to show their offspring. • A10: R = red; r = blue – Heterozygous red = Rr – Homozygous blue = rr – R r r Rr rr r Rr rr Unit 7: Genetics • Q11: Define monohybrid cross? Dihybrid cross? • A11: A monohybrid cross is a cross involving just one trait. A dihybrid cross involves 2 traits Unit 7: Genetics • Q12: State the law of independent assortment? Whose law is it? • A12: Gregor Mendel developed the Law of independent assortment, which states that the genes for each different trait separate independently from one another (i.e., one trait has nothing to do with another trait) • Q13: Explain sex-linked genes, how are traits carried and passed on. • A13: Sex-linked traits are traits that are controlled by genes found only on the X-chromosome. Because females have two X-chromosomes, they have two copies of these traits. Males only have one X-chromosome, so they only have one copy of these traits. These traits can be passed from a mother to her children. Unit 7: Genetics • Q14: Compare and contrast co-dominance and incomplete dominance. Write a problem and draw a punnett square for each type of dominance. • A14: Codominance is when neither trait is dominant; instead, BOTH traits are expressed in equal amounts at the same time. Incomplete Dominance is when neither trait is dominant, but the traits BLEND to produce something that is half-way between the other traits. (Please see this Complex Patterns of Inheritance PowerPoint from the class website for examples) Unit 7: Genetics • Q15: List the four kinds of blood types and explain which ones are dominant, heterozygous and recessive. • A15: 4 possible phenotypes – Type A, B, AB, O • Type A and Type B are CODOMINANT; Type O is RECESSIVE to A and B Unit 7: Genetics • Q16: Can a man be the father of an O blood type child if he has AB blood and the mother has A type blood? • A16: NO! Be sure to show a Punnett Square to prove your answer (Parents: IAIB x IAi) • Q17: Are males able to be carriers of X-linked disorders? Are females? Why or why not? • A17: Males can NOT be carriers of a sex-linked trait. Because males only have one x-chromosome, they only have 1 copy of the gene and cannot, therefore, be carriers. Females, on the other hand, have 2 xchromosomes, so they can be carriers of a sex-linked trait. Unit 7: Genetics • Q18: What is a pedigree and how is it used? What does each symbol on a pedigree represent? Include: shaded, unshaded and partial shaded symbols. • A18: A pedigree is essentially a family tree that shows the inheritance of a genetic trait over many generations. Pedigrees are used to help determine how a trait is inherited. Unit 7: Genetics • Q18: What is a pedigree and how is it used? What does each symbol on a pedigree represent? Include: shaded, unshaded and partial shaded symbols. • A18: A pedigree is essentially a family tree that shows the inheritance of a genetic trait over many generations. Pedigrees are used to help determine how a trait is inherited. Unit 8: DNA • Q19: What is the structure and function of DNA, (be specific and include: the nitrogen base possibilities, sugar and backbone)? • A19: DNA is composed of two strands of nucleotides. Each nucleotide consists of a deoxyribose sugar, a phosphate, and one of 4 nitrogen bases. The shape of a DNA molecule is like a twisted ladder, and it is called a double helix. The sides of the ladder are made of of alternating sugars and phosphates (the sugar-phosphate backbone), and the “rungs of the ladder are made up of the pair nitrogen bases (Adenine, Thymine, Cytosine, and Guanine) Unit 8: DNA • Q20: Name the scientists responsible for identifying the structure of DNA. • A20: The scientists who received the Nobel Prize for their work in determining the structure of DNA are James Watson and Francis Crick. • Q21: Who is given credit for the base pair rules of DNA and what are those rules? • A21: Erwin Chargaff determined that Adenine always pairs with Thymine, and Cytosine always pairs with Guanine. Unit 8: DNA • Q22: Describe the structure of RNA. • A22: RNA is a single-strand of nucleotides (single helix). It contains the sugar RIBOSE, and does not contain the base thymine • Q23: Name the 3 types of RNA and their functions. • A23: The three type of RNA are: – Messenger RNA (mRNA) – delivers the message (gene) to the ribosome – Transfer RNA (tRNA) - brings the amino acid to the ribosome – Ribosomal RNA (rRNA) – makes up the ribosome; helps to assemble the protein Unit 8: DNA • Q24: What base is found only in RNA and not DNA? • A24: RNA does not contain Thymine (T). Instead, it contains the base Uracil (U) • Q25: Explain the process in detail of DNA replication, include the enzymes involved, products made and where it takes place. • A25: DNA replication copies DNA in the nucleus. First, an enzyme (helicase) unwinds the DNA and separates the bases. The original strands are used as a template, and new nucleotides are correctly paired. Another enzyme, DNA POLYMERASE, helps bond the two new molecules together. Unit 8: DNA • Q26: Explain the process of transcription in detail and include the enzyme involved, products made and where it also takes place. • A26: • In transcription, a segment of DNA (gene) in the nucleus is unwound by the enzyme helicase to expose the bases • The DNA is used as a template to make the strand of RNA • RNA nucleotides arrange themselves in order, according to the order of bases on the DNA strand to make a strand of MESSENGER RNA (mRNA) • This mRNA will then leave the nucleus and travel through the cytoplasm to the ribosome to direct the making of the protein Unit 8: DNA • Q27: Explain the process of Translation in detail and include where it takes place and products made. • A27: • The tRNAs, each carrying an amino acid, come to the ribosome and hunt for the correct place on the mRNA strand to put their amino acid • Once they find the correct codon on the mRNA, they leave their amino acid behind, adding it to the growing chain • This process repeats, assembling the correct sequence of amino acids, until a STOP codon is reached • A STOP codon is a 3-base sequence on the mRNA that tells the ribosome to stop adding amino acids to the chain • The amino acids are bonded together using peptide bonds, and a protein (polypeptide) is made! • The CENTRAL DOGMA of Biology: – DNA RNA PROTEIN TRAIT • • • • • • • • Unit 8: Genetics Q28: Define codon. Give the start codon and a stop codon. Define anticodon. When does it get used? A28: Transfer RNA is the molecule that carries the amino acids to the ribosome to be added to the protein tRNA “reads” the code on the mRNA to make sure that the amino acids are assembled in the correct order On one end of the tRNA molecule, there is a special three-base sequence, known as the ANTI-CODON This anti-codon on the tRNA will bond only with is matching 3-base sequence on the mRNA strand (which is called a CODON). The Start Codon is AUG – it tells the process of protein synthesis to get started The STOP codon tells the process of protein synthesis to STOP. Transfer RNA is an RNA molecule that is ‘bent’ into a unique shape. On one end it carries a specific amino acid, and on the other end is the anti-codon that will determine where in the protein chain that amino acid is placed Unit 8: Genetics • Q29: Explain what a mutation is and how it can occur. • A29: A mutation is any change in a DNA sequence. This is often a random mistake that occurs in a cell when the DNA is being synthesized. • Q30: Explain the difference between the 2 types of gene mutations: point and frame shift mutations. Give an example of each. • A30: A point mutation is when only one base in the DNA is changed (substitution). A frameshift mutation occurs when one or more DNA bases is inserted or deleted. This “shifts” the decoding of the gene, and often results in the production of the wrong protein. Therefore, frameshift mutations are often more severe. • Q31: Explain what a silent mutation is and why it is hard to detect. • A31: A “silent mutation” refers to a point mutation that does NOT result in the production of an incorrect amino acid, and therefore has no effect on the organism. They are difficult to detect because they do not change the protein that is being made and the organism remains unaffected. Unit 8: Genetics • Q32: What is a karyotype and how is it used? • A32: A karyotype is essentially a picture of a person’s chromosomes, arranged in their homologous pairs. A karyotype is used to detect disorders caused by chromosomal abnormalities. Unit 9: Evolution • Q33: Explain the theory of evolution. • A33: Evolution is the gradual accumulation of adaptations in a population over time so that the species becomes better adapted to its environment. • Q34: Distinguish between evolution by means of inheritance of acquired characteristics and evolution by means of Natural Selection • A34: Lamarck stated that organisms could gain the traits they needed, then pass those traits on to their offspring (think of stretchy-necked giraffes). Darwin theorized that organisms with the beneficial traits survived and passed on these traits, while those with the traits not suited to the environment did not survive and reproduce Unit 9: Evolution • • Q35: Explain Darwin’s Theory of Natural Selection. A35: Darwin proposed that a process he called Natural Selection causes species to change over time 1. Organisms produce more offspring than can survive, which causes competition for resources(food, water, shelter, mates, etc) 2. There is variation within a species 3. Some variations help the organism better survive in its environment. These organisms are more likely to survive and reproduce, passing their genes on to the next generation 4. Over time, there will be more and more individuals in the population with the favorable trait. So, the whole population gradually changes (EVOLVES) over time to become better adapted to its environment. Unit 9: Evolution • Q36:Describe common misconceptions regarding evolution. • A36: A common misconception about evolution is related to time. Remember, evolution happens very slowly over MILLIONS of years. These huge timescales sometimes make it hard for us to “see” evolution clearly. • One of the most common misconceptions about evolution is that it is a linear process; for example, a monkey “turns in to a human.” This is NOT the case. Evolution is NOT a straight line; it is much better to think of it more as a bush or a tree with many branches • Another common misconception is that individual can adapt and evolve (like Lamarck’s stretchy-necked giraffes). This is NOT how evolution works. Evolution only affects the whole SPECIES, not the individual. Natural Selection is what causes a species to evolve. Unit 9: Evolution • Q37: Identify and explain different types of scientific evidence that supports the theory of evolution. • A37: Darwin’s Theory is supported by many different types of scientific evidence, such as: • Fossils clearly show that many species have changed over time; some fossils show transitional forms (intermediate species between the old and new species) • Continued on next slide… More Evidence for Evolution • • • • Homologous Structures – many species with common ancestry show similar structures. For instance, the forelimbs of many mammals show similar bone structure, implying that there are all modified versions of structures that occurred in a common ancestor Analogous Structures – unrelated species living in similar habitats often have similar structures that serve the same function, such as the fins of a dolphin and a shark Vestigial Structures – many species have body parts that no longer serve any useful purpose, like the pelvic bones of a whale, or your appendix Genetic Evidence – Today, similarities in DNA and amino acid sequences show how species may be related. For example, humans and chimpanzees (our closest living relative) share over 98% of our DNA