Week 1: Review for the Biology End of Course Exam Part 1: The Practice of Science-­‐ defines a problem based on a specific body of knowledge, for example: biology, chemistry, physics, and earth/space science. 1. What is science? Science: •
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Focuses on and attempts to explain the natural world Supports its ideas with evidence Involves scientists and other members of the scientific community. Furthers existing research and leads to new research. Asks testable questions 2. Scientific Method Steps: • Must have a purpose. What are you trying to find out? • Make an observation and conduct research first. The research needs to be from reliable sources. • Make a hypothesis. The hypothesis is an IF, THEN statement. • Perform the experiments. o Variables: § Independent-­‐ what you are testing § Dependent-­‐ the change made to the independent variable § Control-­‐ what stays the same throughout the experiment and remains constant. • Analyze date. Avoid bias. • Draw conclusions. This is based on your data and it confirms or rejects your hypothesis. 3. What makes an experiment reliable? • It has been tested and observed numerous times by more than one group of scientists • The study follows the scientific method. • Only the facts are presented, no personal bias • The information came from a third party that is not profiting from the results of the study. • The study been retested by other scientists with the same results. • The results are reported and published in a scientific journal. 4. Theories and laws. a. Theories are subject to revision and modification over time. b. Laws are developed when observations of the world around us are tested again and again until there is a consensus in the scientific community that the observation, often a relationship in the form of a mathematical equation, is reliable. i. Scientists continue to reevaluate laws whenever new observations are made to make sure the law is consistent with the new observations. Part 2: Organization and Development of Living Organisms a. Describe the scientific explanations of the origin of life on Earth. b. Describe the scientific theory of cells (cell theory) and relate the history of its discovery to the process of science. c. Compare and contrast the general structures of plant and animal cells. d. Compare and contrast the general structures of prokaryotic and eukaryotic cells. 1. The scientific explanations of the origin of life on Earth. a. The major processes needed for the origin of life on Earth may include: i. the presence of small organic molecules (through spontaneous synthesis or from meteorites) ii. assembly of these molecules into larger organic molecules/polymers (such as RNA and protein) iii. RNA molecules become self-­‐replicating iv. the packaging of groups of molecules into microspheres that are able to maintain an internal chemistry different from surroundings 2. The Cell Theory: a. All living things are made up of cells. b. The cell is the basic unit of structure and in all living things. c. New cells can only be produced from existing cells. (Many scientists worked together to develop the Cell Theory. Scientists developed the Cell Theory through continued experimentation, observation, and advances in technology.) 3. Prokaryotes and Eukaryotes. a. Prokaryotes i. Contain DNA ii. NO Nucleus iii. Can only be single-­‐celled organisms iv. Only a few organelles v. Very basic b. Eukaryotes i. Animal Cells and Plant Cells are Eukaryotic Cells ii. Contain DNA iii. Have a Nucleus iv. Can be single-­‐celled OR as part of multi-­‐celled organisms v. Contain many organelles vi. Membrane bound organelles 4. Comparing plant and animal cells a. Cell Membrane: Selective barrier for the cell, allows some things to pass into or out of the cell but not others. b. Nucleus: Large and usually close to the center. Contains most of the cell’s genetic information. c. Cytoplasm: Thick fluid that fills up a cell and surrounds all of the organelles. d. Ribosomes: Found in cytoplasm or attached to the rough endoplasmic reticulum. Responsible for protein synthesis. e. Rough Endoplasmic Reticulum(ER): Covered with ribosomes. Responsible for making and storing proteins. Creates vesicles to carry new proteins to the Golgi apparatus f. Smooth ER: Various functions such as detoxifying harmful substances g. Golgi Apparatus: Responsible for modifying and storing proteins h. Lysosomes: Contain enzymes which break down large molecules to be used by the cell. i. Vacuoles: Store food, water, minerals, etc. j. Mitochondira: Powerhouse of the cell k. Cell Wall: surrounds the cell membrane and provides an additional layer of protection for plant cells. l. Chloroplasts: Contain chlorophyll and use energy from the sun to make glucose Part 3: Heredity and Reproduction a. Use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance. b. Describe the basic process of DNA replication and how it relates to the transmission and conservation of the genetic information. c. Evaluate the impact of biotechnology on the individual, society and the environment, including medical and ethical issues. d. Compare and contrast mitosis and meiosis and relate to the processes of sexual and asexual reproduction and their consequences for genetic variation. 1. Mendel’s laws. a. Different forms of a gene account for variations in the inherited traits. b. An organism inherits two genes for each trait, one from each parent. c. Some alleles dominate over others for a given trait. d. The two genes of a given trait segregate during gamete production. 2. Patterns of Inheritance a. Phenotype: The physical expression of a trait from allele combination. b. Genotype: The gentic expression of allele combinaitons. c. Dominant: An allele that is expressed in the phenotype and mask the expression of a recessive allele d. Recessive: An allele that will not be expressed in the phenotype unless the organism is homozygous for this trait e. Homozygous: Having IDENTICAL alleles for a given trait (AA or aa) f. Heterozygous: Having two different alleles for a given gene (Aa) 3. Cell division: Mitosis vs. Meiosis 4. DNA a. Model of DNA The DNA model is described as a double helix. b. DNA consists of nitrogenous bases and sugar-­‐phosphate units. The bases are in the center like the rungs on a ladder. Hydrogen bonds hold these bases together in the DNA molecule. c. A nucleotide is made up of three parts: a nitrogenous base, a sugar molecule, a phosphate molecule. The nucleotide is a group that repeats over and over to make a very large molecule of DNA. d. DNA is composed of four nitrogenous bases: Adenine, Guanine, Thymine, Cytosine. The strands of DNA are complementary, which means that if you know the bases on one side of the ladder, you can always tell what the bases on the other side will be; Adenine (A) always pairs with Thymine (T) and Guanine (G) always pairs with Cytosine (C). e. 5. DNA Replication a. Step 1: The DNA double helix "unzips." An enzyme called DNA helicase attaches to the DNA molecule (double helix) and moves along the molecule and "unzips" the two strands of DNA. b. Step 2: There are complementary nucleotides floating around in the nucleus. That means there are A, G, T and C’s floating around in the nucleus. These bases form hydrogen bonds with the bases in the DNA strands. c. Step 3: The enzyme called DNA polymerase catalyzes the formation of the sugar-­‐
phosphate units along the side of the "ladder." The sugar-­‐phosphate units connect one base pair (or rung on the ladder) to the next one. Result: Two new DNA molecules result from the replication -­‐ each molecule with a strand of old DNA and a strand of new DNA. Transcription – the first step in the process of getting instructions off the DNA and out into the cytoplasm • Step 1: In transcription, the DNA unzips like it did during DNA replication. One strand of DNA is "transcribed" or "copied" by an enzyme to make a messenger RNA (mRNA) molecule. Remember that RNA molecules use the base U to bind to A instead of T. • Step 2: Once the mRNA has transcribed the message, it breaks away from the DNA strand. The DNA then "rezips" back to its double helix shape. • Step 3: The coding that the mRNA carries is a sequence of three nucleotides called a codon (a three-­‐letter word that selects for the amino acid). The mRNA will carry the instructions from the nucleus to the cytoplasm. Translation : Creates proteins • Step 1: After the mRNA leaves the nucleus, it floats around in the cytoplasm. Out in the cytoplasm, there are also different kinds of RNA molecules, called transfer RNA molecules (tRNA for short). tRNA molecules have a 3 nucleotide code on one end, and a specific kind of amino acid on the other end. • Translation Step 2: In the cytoplasm, the mRNA attracts a ribosome and molecules with the matching three letter code form a temporary bond to the mRNA. The amino acids on the tRNA molecules bond forming a protein chain. •
Translation Step 3: The growing chain is complete when a stop codon is reached. The completed chain breaks away. This chain of amino acids is the completed protein. 6. Biotechnology • Transgenic Organisms o Organisms with traits produced by recombinant DNA are called transgenic. Genetic engineers are now able to produce transgenic plants, animals, and microorganisms; many are used to improve the plants and animals for agricultural purposes. • Cloning o A group of cells or an organism produced asexually from one ancestor, to which they are genetically identical uses a single cell from an adult organism to grow an entirely new individual. • DNA fingerprinting o A tool used by biologists that determines whether two samples of DNA are related by analyzing an individual's unique collection of DNA segments. In addition to matching a tissue sample to a specific individual, DNA fingerprinting can also be used to establish biological relationships between relatives and wildlife conservation.