Science Final Exam Notes PDF

Science Final Exam Notes Chapter 1: DNA & Genetics Watson & Crick Model of DNA (Deoxyribonucleic Acid) - DNA has a similar structure in all organisms in that it is made up of sm...

Science Final Exam Notes Chapter 1: DNA & Genetics Watson & Crick Model of DNA (Deoxyribonucleic Acid) - DNA has a similar structure in all organisms in that it is made up of smaller molecules called nucleotides. - The nucleotide is made up of the deoxyribose sugar, the nitrogenous base and the phosphate - Forms in a twisted rope ladder - Complementary base pairing: adenine pairs with thymine (apples in the tree), cytosine pairs with guanine (cars in the garage) Mitosis and Meiosis DNA Replication 1. Strands of the double helix ‘unzip’ from each other through the enzyme helicase 2. Free floating nucleotides pair up with the exposed base pairs done by DNA polymerase 3. Two strands are rejoined together, nitrogen bonds reestablished DNA ligase Mitosis 1. Interphase: DNA replication = two sets of chromosomes, centrosomes begin to appear 2. Prophase: Chromosomes condense, spindle fibres appear, nucleus disappears, centrosomes go to opposite poles 3. Metaphase: spindle fibres attach to the chromosomes, chromosomes line up at the equator 4. Anaphase: Sister chromatids are pulled apart, cell elongates 5. Telophase: chromatids arrive and begin to decondense, spindle fibres break down, nucleus and nucleolus appears 6. CYTOKINESIS Meiosis - For gametes - PRETTY MUCH the same as mitosis, just happens twice, second time no replication and in prophase 1, crossing over Genes, Traits, & Alleles - Traits: category of characteristics you present, e.g. eye colour - Genes: section of a chromosome that codes for a characteristic - Alleles: alternate forms of the same gene - Dominant trait: only one copy of the allele required to express the trait - Recessive trait: two copies of the allele required to express the trait - Genotype: set of genes - Phenotype: set of observable characteristics Sex Linked Traits - Genes that are expressed as traits can be located in the autosomal cells or gametes - Autosomal traits: traits located on autosomes, expressed equally between males and females Mutations - Silent mutations: changes in the code that do not affect the individual, single base is changed - Missense mutations: different protein produced, may not function correctly or cause disease (sickle cell anemia)  - Nonsense mutations: causes the cells to stop reading the information on the gene so the protein create is incomplete and cannot function at all (cystic fibrosis) - Frameshift mutations: insertion or deletion of a single base which causes all the information following it to become jumbled so that it cannot be ‘read’ to make a protein. (Tay-Sachs disease) Pedigree Charts and Punnet Squares - Pedigree charts can be used to observe patterns and predict the inheritance of traits within families - -  - - In a Punnett square, the possible gametes produced by one parent are shown across the top. The gametes from the other parent are shown down the side. In each square is a possible outcome of fertilisation. Biotechnology Development of Vaccines: - Vaccines work by causing a reaction in your body that responds to a pathogen - Done by exposing your body to a small amount of poison from the bacterium to make it inactive or using dead bacteria. - This does not harm your body but triggers the same antibodies to produce, causing you to become immune to that specific pathogen. Making vaccines using the Genome: - Bacteria have various proteins on their surface, some of these proteins are used to produce antibodies - Genome: set of DNA instructions found in a cell. - Scientists complete the genome of the bacterium to identify the genetic code that causes the surface proteins to be produced - The genes of those proteins are isolated and spliced(joined/inserted) into the plasmids of the E coli which produce the proteins coded for by the spliced genes. - Some of the proteins will be produced in larger quantities than Others. The proteins produced in large quantities are purified and then tested on mice. The blood of the mice is later analysed for  antibodies. Proteins that caused the greatest antibody production are tested further. Finally, two or three proteins go through human clinical trials before being released for general use. Stem Cells: - When an embryo is a few days old, it contains cells that are capable of becoming any other type of cell in the human body (known as pluripotent) - These cells are known as embryonic stem cells - Can be used to help patients recover from spinal board injuries, heart attacks, brain and nerve damage Adult Stem Cells: - These cells are found deep within organs that need a consistent supply of new cells e.g. skin - These stem cells are only able to become certain types of cells (compared to embryonic stem cells) depending on where they are found In-Vitro fertilisation: - IVF is the process of fertilising eggs outside the human body then placing the developing embryo back into the woman’s uterus - Typically used for couples who are infertile or who have trouble conceiving a baby naturally - Eggs and sperm are joined on a petri dish and placed in an incubator at 38 C° where fertilisation should occur in 18-24 hours. Gene Splicing - Chapter 3: Natural Selection & Evolution Fossil records & index Strata identification Analogous and Homologous Structures - In related species, characteristics that have the same basic structure are called homologous characteristics. These characteristics are controlled by particular inherited genes. - The more alike two organisms are, the more genes they share. As you move from higher levels of classification (kingdom) to the lower levels (genus and species), the more alike those genes become. - A homologous structure does not necessarily have the same function - Structures that look similar on genetically very different organisms are known as analogous Artificial Selection - Artificial selection is the process by which humans choose certain desirable traits to breed  - This process occurs over generations and occasionally new mutations that occur in the breeders are NOT present in wild birds - E.g. wild budgerigars are green and yellow, humans have breeded blue budgerigars Darwin’s Theory of Evolution - Darwin proposed that species had a common ancestor but over many generations had evolved to suit their different environments and feeding habits - Darwin suggested that the mechanism of evolution was natural selection. - Organisms that are well suited to their environment are more likely to survive and produce offspring, organisms that are not well suited to their environment are out-competed and die young. As a result, more desirable traits populate a species and are passed on. - The environmental factor that acts on the population is known as a selective agent - Darwin concluded that natural selection occurs through variation - Variation is caused by differences in genes which are then passed on to offspring Speciation - Speciation is the process by which one species splits into two or more different species - Speciation has resulted in biodiversity, a range of different species - Step 1: Variation There must be variation in the population, natural selection can only act on variation present within the population. - Step 2: Isolation Different groups of the population are prevented from interbreeding by some mechanism, stopping gene flow throughout a population. This can occur in a number of ways, such as geographic or climatic barriers. - Step 3: Selection Natural selection that affects the genotype causes changes that prevent the groups breeding, thus speciation has occurred Evidence for Evolution - Fossils: analysing the fossil record shows that there is an increasing number of species that have lived on Earth, biodiversity=speciation. Fossils also show transitional forms, showing changes overtime between groups. - Comparative anatomy: this compares the structure of organisms of both living species and fossils to determine homologous structures between species, e.g. pentadactyl limbs (pictured) - DNA and protein structure: organisms that have similar anatomy show more genes in common that organisms that are less alike. Two species and their common ancestor would have similar DNA. This done by comparing how many amino acids are in same position on a protein.  - Distribution of current species: unique species occur on isolated islands, this is expected as isolation allows speciation to occur - Embryology: the study of the development, structure and function of embryos show similarities across species, pointing to a common ancestor Chapter 2: Geological Time Fossils - The fossil record lists all the species of living organisms that have been found as fossils as well as their location and relative age. - Formation of a fossil: 1. Organism dies and is covered by sediment. Soft parts decay 2. More sediment covers the organism. It may either remain or be replaced with minerals 3. After millions of years of compression, movement of the crust may thrust up the layer of sedimentary rock containing the fossil. 4. Weathering and erosion wards away some of the rock, exposing the fossil - Types of fossils include - Trace - Mould - Cast - Trueform Relative Dating - Layers of sedimentary rock are called strata - Lower strata are older than the strata above because sedimentary rock builds over time - By comparing layers of strata, you can determine the relative age of fossils to other - This is done through using Index fossils which are widespread, abundant, easy to identify and lived in a relatively short period of time. Chapter 8: Motion & Energy Distance and displacement - Distance is a scalar quantity, measuring just the magnitude, whereas, displacement is a vector quantity, measuring magnitude and direction  - Speed - Speed is a scalar quantity measuring the rate of change in DISTANCE - Average speed is the measure of how fast something moves overall, across a whole journey - Instantaneous speed is the speed at a particular moment in time, for instance, a speedometer - Speed is calculated through distance over time - The SI unit for distance is metres, and for time is seconds, so the SI unit for speed is m/s Velocity - Vector quantity for measuring the rate of change in DISPLACEMENT - Speed and Velocity are relative quantities - Velocity is calculated for displacement over time Acceleration - In physics, acceleration is a measure of the rate at which something changes speed as opposed to just a change in speed. - - The unit above is km/h/s because it displays the increase in speed (km/h) per second - The SI unit for acceleration is m/s/s or m/s2 - A falling object accelerates towards Earth because of the force of gravity. Acceleration due to gravity is 9.8 m/s2 acceleration at this magnitude is 1 g - Friction between the air and the moving object (air resistance) will eventually reduce this acceleration to zero (terminal velocity) - Graphing Motion Distance-Time - Shows how far an object travels as time progresses. - Flat line: motion has stopped - Steep slope: the object is moving faster than a line of gentle slope - The slope or gradient of a distance–time graph is equivalent to the object’s average speed over a time interval. - Displacement-Time - Horizontal line: the object is stationary (not moving because the displacement does not change) - Sloping line: the object is moving. - Gradient: velocity of the object Speed-time - Flat line: constant speed - Slope: acceleration - Gradient: the steeper, the greater acceleration. Negative gradient indicates deceleration - Area under line is distance travelled Newton’s First Law - An object at rest will remain this way unless it is acted upon by a force. An object that is moving will continue to move at the same speed and in the same direction unless an unbalanced force acts upon it. - The tendency to resist any change in motion is called an object’s inertia. The larger the mass of an object, the greater its inertia, and the harder it is to change its motion. - E.g. falling backwards when the train starts as your body remains stationary = inertia Newton’s Second Law - An object will accelerate in the direction of an unbalanced force acting upon it. The size of this acceleration depends upon the mass of the object and the size of the force acting. - F=ma Newton’s Third Law - For every action force there is an equal and opposite reaction force. - According to Newton’s second law, the acceleration that an object experiences due to a force depends upon its mass. Although the size of action and reaction forces is the same, an object of low mass will travel with much greater acceleration than a more massive object. Kinetic & Potential Energy - Energy of a moving object is called kinetic energy. The amount of kinetic energy an object has depends upon its mass and its speed. Kinetic energy = ½ x mass x velocity2 - Potential energy is energy that an object has because of its position or structure. GPE=mgh  - An object positioned above the ground has gravitational potential energy. A stretched or compressed spring has elastic potential energy. Energy Efficiency - The efficiency of an energy transfer is a measure of how much useful energy is produced. -