Genetics PDF

Genetics State where DNA is located in the cell: Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA). Recall which cells have DNA. In prokaryotes, the DNA (chromoso...

Genetics State where DNA is located in the cell: Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA). Recall which cells have DNA. In prokaryotes, the DNA (chromosome) is in contact with the cellular cytoplasm and is not in a housed membrane-bound nucleus. In eukaryotes, however, the DNA takes the form of compact chromosomes separated from the rest of the cell by a nuclear membrane (also called a nuclear envelope). Describe what genes are. A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes act as instructions to make molecules called proteins, which are needed for the body to function. However, many genes do not code for proteins, instead they help control other genes. Describe what chromosomes are Chromosomes are threadlike structures made of protein and a single molecule of DNA that serve to carry the genomic information from cell to cell Recall that DNA is arranged in a double helix. Each molecule of DNA is a double helix formed from two complementary strands of nucleotides held together by hydrogen bonds between G-C and A-T base pairs Explain how nucleotides are arranged to form a sugar phosphate backbone The bases bind to one other via hydrogen bonding to secure the nucleotide to the template strand. The protein DNA ligase then fuses the sugar-phosphate groups of adjacent nucleotides to create the DNA backbone. Identify and name the three molecules that make up a nucleotides The three molecules that make up a nucleotide are phosphate, pentose sugar, and nitrogenous bases. Name the four nitrogenous bases in DNA The four nitrogenous bases are adenine, guanine, cytosine, uracil, and thymine. Name the rule that states that the bases have specific bonding partners The rules of base pairing explain the phenomenon that whatever the amount of adenine (A) in the DNA of an organism, the amount of thymine (T) is the same (called Chargaff's rule). Similarly, whatever the amount of guanine (G), the amount of cytosine (C) is the same. Explain when and why mitosis is needed It plays an important part in the development of embryos, and it is important for the growth and development of our bodies as well. Outline the steps of mitosis Interphase The stage in the life cycle of a cell where the cell grows and DNA is replicated Prophase Prophase is the first stage of mitosis. In prophase, - chromosomes condense and become visible - spindle fibres emerge from the centrosomes - nuclear envelope breaks down  - nucleolus disappears Prometaphase Prometaphase is the second stage of mitosis. In prometaphase, - chromosomes continue to condense - kinetochores appear at the centromeres - mitotic spindle microtubules attach to kinetochores - centrosomes move toward opposite poles Metaphase Metaphase is the third step in mitosis. In mitosis, - mitotic spindle is fully developed, centrosomes are at opposite poles of the cell - chromosomes are lined up at the metaphase plate - each sister chromatid is attached to a spindle fiber originating from opposite poles Anaphase Anaphase is the fourth step in mitosis. In anaphase, - cohesin proteins binding the sister chromatids together break down - sister chromatids (now called chromosomes) are pulled toward opposite poles - non-kinetochore spindle fibres lengthen, elongating the cell Telophase Telophase is the fifth step in mitosis. In telophase, - chromosomes arrive at opposite poles and begin to decondense - nuclear envelope material surrounds each set of chromosomes - the mitotic spindle breaks down Cytokinesis Cytokinesis is the sixth and final step of mitosis. In cytokinesis, - Animal cells: a cleavage furrow separates the daughter cells - Plant cells: a cell plate separates the daughter cells Compare the DNA in daughter cells to the DNA found in their parent cells Mitosis produces two genetically identical “daughter” cells from a single “parent” cell, whereas meiosis produces cells that are genetically unique from the parent and contain only half as much DNA. Explain what meiosis is used for Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. This process is required to produce egg and sperm cells for sexual reproduction. Outline the steps that are involved in meiosis Meiosis I Prophase I The nuclear envelope disintegrates. Chromosomes begin to condense. Spindle fibres appear. Prometaphase II Spindle fibres attach to the chromosomes at the centromere. Metaphase I The homologous chromosomes align at the equatorial plate ensuring genetic diversity among offspring. Anaphase I The homologous chromosomes are pulled towards the opposite poles. Telophase I Spindle fibres disappear. Nuclear envelope is reformed. Cytokinesis I The cytoplasm and the cell division result in 2 non-identical haploid daughter cells. Meiosis II Prophase II The chromatin condenses into chromosomes. Nuclear envelope disintegrates. Centrosomes migrate to either poles. Spindle fibres are reformed. Metaphase II The chromosomes align along the equatorial plate. On the contrary, the chromosomes in metaphase I were in homologous pairs. Anaphase II Sister chromatids are pulled to the opposite poles. Telophase II Nuclear envelope redevelops and the spindle fibres disappear. Cytokinesis II The cytoplasm and cell divide producing 4 non-identical haploid daughter cells. Explain the difference between a haploid and a diploid cell. A haploid cell has only a single set of chromosomes. Most cells in humans are diploid rather than haploid, meaning they have two copies of each chromosome. State the number of rounds of division that occur in mitosis and meiosis. Meiosis 2 rounds Mitosis 1 round Distinguish the differences between homologous chromosomes and sister chromatids. Sister chromatids are identical copies of a single chromosome. Homologous chromosomes are pairs of chromosomes that are similar in size, shape, and gene content. Comparison of Daughter Cells in Mitosis vs. Meiosis: Mitosis: Produces two genetically identical daughter cells, each with the same number of chromosomes as the parent cell (diploid in humans, 46 chromosomes). Meiosis: Produces four genetically unique daughter cells, each with half the number of chromosomes as the parent cell (haploid, 23 chromosomes in humans). This process is key for producing gametes, like sperm and egg cells. Function of Gametes: Gametes are reproductive cells (sperm in males, eggs in females) that combine during fertilisation to form a new organism. They carry half the genetic information from each parent, ensuring genetic diversity. Definition of Fertilisation: Fertilisation is the process where a sperm cell fuses with an egg cell to form a zygote, which has a complete set of chromosomes and develops into an embryo. Why Gametes Are Haploid: Gametes need to be haploid so that when they combine during fertilisation, the resulting zygote has a full set of chromosomes (diploid) instead of doubling the chromosome number with each generation. Chromosomes in Gametes vs. Other Body Cells: Gametes have 23 chromosomes (haploid) in humans, whereas all other somatic (body) cells have 46 chromosomes (diploid). Role of Nucleotide Sequences in Making Proteins: Nucleotide sequences in DNA provide the instructions for assembling amino acids into proteins. These sequences determine the order of amino acids, which affects the protein’s structure and function. Connection Between Proteins and Genes: Genes are sections of DNA that code for proteins, which carry out various functions within cells. Proteins are the products of gene expression. Difference Between Genes and Alleles: A gene is a segment of DNA that codes for a trait, while an allele is a variation of that gene (e.g., the gene for eye colour might have alleles for blue or brown eyes). Dominant and Recessive Traits Notation: Dominant traits are represented by uppercase letters (e.g., A for dominant allele), and recessive traits are represented by lowercase letters (e.g., a for recessive allele). Genotypes vs. Phenotypes: Genotype: The genetic makeup of an organism (e.g., AA, Aa, aa). Phenotype: The observable characteristics or traits (e.g., brown eyes, blue eyes). Homozygous and Heterozygous Definitions: Homozygous: An organism with two identical alleles for a trait (e.g., AA or aa). Heterozygous: An organism with two different alleles for a trait (e.g., Aa). Identifying Dominance Based on Heterozygous Phenotypes: If the phenotype of a heterozygous individual (e.g., Aa) displays the dominant trait, then that allele is dominant. If only one allele is expressed, the non-expressed allele is recessive. Using Homozygous Dominant, Heterozygous, and Homozygous Recessive for Genotypes: Homozygous Dominant (AA): Shows dominant phenotype. Heterozygous (Aa): Shows dominant phenotype. Homozygous Recessive (aa): Shows recessive phenotype. Punnett Square Construction: A Punnett square visualises potential genotypes for offspring based on the genotypes of the parents. Calculating Probability of Genotype/Phenotype: Probabilities can be calculated from Punnett squares as ratios of possible genotypes (e.g., 1 AA : 2 Aa : 1 aa) or phenotypes (e.g., 3 dominant : 1 recessive). Genotypic and Phenotypic Ratios: Genotypic ratio: the proportion of different genotypes (e.g., 1:2:1 for AA:Aa ). Phenotypic ratio: the proportion of observable traits (e.g., 3:1 for dominant ). Sex-Linked Traits Explanation: Traits associated with genes on the sex chromosomes, especially the X chromosome, are sex-linked. They often affect males and females differently. Definition of Hemizygous and Its Relevance to Males: Hemizygous means having only one copy of a gene instead of the typical two. Males are hemizygous for X-linked genes because they have only one X chromosome. Males and X-Linked Phenotypes: Males are more likely to express X-linked traits because they have only one X chromosome, so any recessive allele on the X chromosome will be expressed without a second X to potentially mask it. Pedigree Symbols Interpretation: Pedigrees use standardised symbols to show the inheritance of traits, such as squares for males, circles for females, shaded symbols for affected individuals, and unshaded for unaffected ones. Pedigree Analysis to Predict Inheritance: Pedigrees can trace traits through generations, helping to predict the likelihood of traits appearing in offspring. Environmental Earth's Spheres and Their Interactions: Geosphere: The solid Earth, including rocks, minerals, and landforms. Hydrosphere: All water on Earth, including oceans, rivers, lakes, and groundwater. Atmosphere: The layer of gases surrounding Earth. Biosphere: All living organisms, including plants, animals, and microorganisms. Cryosphere: The frozen parts of the Earth, including glaciers, snow, and ice caps. Interactions Examples in the Sunshine Coast Biosphere: Geosphere and Hydrosphere: Coastal erosion shapes beaches. Biosphere and Atmosphere: Plants in the area take in carbon dioxide during photosynthesis. Cryosphere and Hydrosphere: Melting ice contributes to sea level changes, impacting coastal regions. Sources of Atmospheric Carbon Dioxide: Natural sources include respiration, volcanic eruptions, and decomposition. Human-made sources include burning fossil fuels, deforestation, and industrial processes. The Carbon Cycle: Carbon moves through Earth's spheres via processes like photosynthesis, respiration, decomposition, and combustion. It’s stored temporarily in plants (biosphere), dissolved in oceans (hydrosphere), and held in rocks or fossil fuels (geosphere). Carbon Sinks: Carbon sinks, like forests, soil, and oceans, absorb more carbon than they release, storing it for long periods and reducing the amount in the atmosphere. Greenhouse Effect: Greenhouse gases trap heat in Earth’s atmosphere, maintaining a stable temperature. However, excess CO₂ from human activities intensifies this effect, leading to global warming. Impact of Rising Carbon Dioxide on Climate Change: Higher CO₂ levels increase Earth’s temperature, affecting weather patterns, ocean currents, and ecosystems worldwide. Climate Change and Local Ecosystems: In coastal regions near the Sunshine Coast, rising sea levels, warmer temperatures, and changing rainfall patterns could affect marine life, increase erosion, and threaten local biodiversity. Climate Action Plan to Minimise Impact: Reduce Emissions: Use renewable energy, improve energy efficiency. Protect Natural Carbon Sinks: Preserve forests and marine ecosystems. Promote Sustainable Practices: Encourage recycling, reduce waste.  Educate and Advocate: Raise awareness on sustainable practices. The Water Cycle: Water moves through evaporation, condensation, precipitation, infiltration, and runoff, linking Earth’s spheres in a continuous cycle. Water Cycle Diagram: Include labelled processes: evaporation, condensation, precipitation, runoff, and infiltration. Human Impact on the Water Cycle: Pollution, deforestation, and urbanisation alter the natural water flow, reduce groundwater recharge, and increase runoff and erosion. Temperature and Global Pressure Systems: Temperature affects pressure: warm air rises (low pressure), and cool air sinks (high pressure). These differences drive wind patterns. Pressure Systems, Wind, and Weather: Pressure systems (high and low) create wind patterns that influence weather. Low-pressure systems bring clouds and rain, while high-pressure systems bring clear weather. Winds and Ocean Surface Currents: Winds drive surface currents in the ocean, impacting climate and weather along coastlines. Ocean Currents Driven by Pressure, Salinity, and Density: Differences in water density, caused by temperature and salinity, create deep currents. Warmer, saltier water is less dense and tends to stay at the surface, while colder, saltier water sinks. Surface vs. Deep Ocean Currents: Surface Currents: Driven by wind, affecting the upper ocean. Deep Currents: Driven by density differences, influencing ocean circulation at deeper levels. Using Transects, Quadrats, and Biodiversity Measures to Compare Ecosystems: Transects: Used to study changes in vegetation or species distribution along a line. Quadrats: Used to measure species abundance and diversity in a defined area.  Biodiversity Measures: Indicators like species richness and evenness provide insight into ecosystem health and resilience. Organisms Adapt to Change Natural Selection: Natural selection is the process by which organisms better adapted to their environment tend to survive and reproduce more successfully, passing on their advantageous traits to the next generation. Over time, this leads to the accumulation of beneficial traits within a population. Mechanisms Leading to Evolutionary Change: Evolutionary change occurs through several mechanisms, including: ○ Natural Selection: The differential survival and reproduction of organisms based on their traits. ○ Mutations: Random changes in DNA that can introduce new traits. Mutations can be beneficial, harmful, or neutral, depending on the environment. ○ Genetic Drift: Random fluctuations in allele frequencies in a population, often impacting smaller populations. ○ Gene Flow: The movement of genes between populations, which can introduce new traits and increase genetic diversity. Evolutionary Theories Before Darwin: Lamarckism: Proposed by Jean-Baptiste Lamarck, suggesting that traits acquired during an organism's lifetime (like a giraffe’s long neck) could be passed down to offspring. Catastrophism: Georges Cuvier’s theory that Earth's history was shaped by sudden, short-lived, violent events, leading to extinctions and subsequent creation of new species. Uniformitarianism: Charles Lyell’s idea that geological processes observed in the present operated in the past at similar rates, suggesting a much older Earth. Darwin's Theory of Evolution: Darwin’s theory, often called descent with modification, posits that all species arise from a common ancestor and evolve through natural selection. Over many generations, this process leads to the formation of new species as organisms accumulate adaptations to their environments. Concepts of Natural Selection and Common Ancestry: Natural Selection: The driving force of evolution, favouring individuals with advantageous traits. Common Ancestry: The concept that all species share a common ancestor, with branching patterns of evolution giving rise to diverse life forms. Mechanisms of Evolutionary Change: Natural Selection: Drives adaptation by favouring beneficial traits. Mutations: Introduce genetic variation, which is essential for evolution. Genetic Drift: Random changes in allele frequencies can lead to evolutionary change, especially in small populations. Gene Flow: Increases genetic diversity by transferring alleles between populations. How These Processes Drive Evolutionary Change: Combined, these processes increase genetic variation and shape populations over generations. Natural selection acts on the variation created by mutations, genetic drift, and gene flow, leading to the evolution of new adaptations and, over time, new species.