Genes and DNA PDF

Genes and DNA 1. What are Genes and What Are They Made Of? ○ Genes are segments of DNA that serve as instructions for making proteins, which perform various functions in the body. ○ They are made up of DNA (Deoxyribonucleic Acid), a molecule that contains t...

Genes and DNA 1. What are Genes and What Are They Made Of? ○ Genes are segments of DNA that serve as instructions for making proteins, which perform various functions in the body. ○ They are made up of DNA (Deoxyribonucleic Acid), a molecule that contains the genetic code. 2. DNA: Definition and Function ○ Definition: DNA is a double-stranded molecule in the shape of a double helix that carries genetic information. ○ Functions: Stores genetic instructions for the development, function, growth, and reproduction of living organisms. Guides protein synthesis. 3. Parts of the DNA Double Helix ○ Sugar-Phosphate Backbone: Made of alternating sugar (deoxyribose) and phosphate groups. ○ Nitrogenous Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G) pair specifically (A-T, C-G) through hydrogen bonds. Key Genetics Terms 1. Haploid: A cell with one set of chromosomes (e.g., sex cells like sperm and eggs). 2. Diploid: A cell with two sets of chromosomes (e.g., most body cells). 3. Genotype: The genetic makeup of an organism (e.g., AA, Aa). 4. Phenotype: The observable traits of an organism (e.g., blue eyes). 5. Allele: Different forms of a gene (e.g., dominant or recessive). 6. Gene: A unit of heredity passed from parent to offspring. 7. Chromosome: A structure of DNA that carries many genes. Types of Reproduction 1. Asexual Reproduction: ○ Involves one parent. ○ Produces genetically identical offspring (clones). ○ E.g., binary fission in bacteria. 2. Sexual Reproduction: ○ Involves two parents. ○ Produces genetically diverse offspring. ○ Requires the fusion of sex cells (gametes). Why Are Sex Cells Needed in Reproduction? They carry half the genetic information from each parent, allowing offspring to inherit traits from both. Cell Division 1. Mitosis: ○ Purpose: Growth, repair, and asexual reproduction. ○ Results: Two identical diploid daughter cells. 2. Meiosis: ○ Purpose: Produces gametes (sperm and egg cells). ○ Results: Four haploid cells with genetic variation. Differences: Mitosis: One division; no genetic variation. Meiosis: Two divisions; results in genetic variation. Punnett Squares and Genetic Inheritance 1. Constructing a Punnett Square: ○ Cross alleles of parents (e.g., AA x Aa) to find possible offspring combinations. 2. Calculating Phenotype Percentages: ○ Count how many squares show a trait and divide by the total number of squares. How Gametes Determine Characteristics: Gametes carry alleles. The combination from both parents determines offspring traits. When Heredity Goes Wrong: Mutations in DNA or errors during meiosis can lead to genetic disorders or diseases. Genetically Modified Organisms (GMOs) 1. Definition: Organisms whose DNA has been altered using genetic engineering techniques. 2. Pros: ○ Increased crop yields.  ○ Resistance to pests and diseases. ○ Potential medical benefits. 3. Cons: ○ Ethical concerns. ○ Possible environmental impacts. ○ Potential allergenicity. Ionising Radiation 1. Effects on Elements: ○ Can ionize atoms by removing electrons, leading to changes in chemical properties. ○ Can cause mutations or damage in living cells. 2. Use: Sterilizing medical equipment or food preservation.