Prokaryotic vs. Eukaryotic Cells Guide

📚 GENETICS STUDY GUIDE – QUIZ 2 🔬 Prokaryotic vs. Eukaryotic Cells Feature Prokaryotic Cells Eukaryotic Cells Found In (Kingdoms) Bacteria, Archaea Plants, Animals, Fungi, Protists Size Small (1–10 µm) Larger (10–100 µm) Nucleus No nucleus Has a nucleus (stores DNA) Organelles No membrane-bound organelles Has membrane-bound organelles DNA Location Free in cytoplasm (nucleoid) Inside nucleus 🧩 Protein Structures 1.​ Primary – Chain of amino acids. 2.​ Secondary – Coiling or folding (like a helix or sheet). 3.​ Tertiary – 3D shape of the entire protein. 🧬 DNA, Chromosomes, and Related Terms ●​ Genome: All of an organism’s DNA. ○​ Chromosome Number: 2n (diploid). For example, humans have 46 chromosomes (23 pairs, 2n = 46). ●​ DNA: The molecule that carries genetic information. ○​ Chromosome Number: Found in chromosomes (2n, n, 4n depending on cell type and stage). ●​ Gene: A segment of DNA that codes for a specific protein. ○​ Chromosome Number: Located on chromosomes, but not a separate entity with a specific chromosome count. ●​ Allele: A variant of a gene (e.g., A or a). ○​ Chromosome Number: Same as gene because alleles are versions of genes located on chromosomes. ●​ Chromatin: DNA + histone proteins; loose form of DNA before it condenses into chromosomes. ○​ Chromosome Number: Present in the nucleus during interphase (before cell division), chromatin is not yet fully condensed into chromosomes. ●​ Histones: Proteins that help package DNA into chromatin. ○​ Chromosome Number: Same as the number of chromosomes because histones help organize DNA into chromosomes. ●​ Chromosome: A structure made of tightly coiled DNA, visible during cell division. ○​ Chromosome Number: Typically 2n in somatic cells (body cells), which means pairs of chromosomes. E.g., Humans have 46 chromosomes (2n = 46) in body cells. ●​ Chromatid: One half of a duplicated chromosome. ○​ Chromosome Number: During cell division, chromosomes are duplicated. For example, in the S phase(DNA replication), chromosomes are in the form of 4n (4 copies of chromosomes in total, 2 chromatids per chromosome). ●​ Epigenome: Chemical tags on DNA that regulate gene activity (does not change the DNA sequence itself). ○​ Chromosome Number: No specific number as it refers to chemical modifications across the entire genome. Chromosome Number (Summary) 1.​ 2n (Diploid): Found in somatic (body) cells. Humans have 46 chromosomes (23 pairs of homologous chromosomes). 2.​ n (Haploid): Found in gametes (sperm/egg). Humans have 23 chromosomes in each gamete (no pairs). 3.​ 4n (Tetraploid): A rare case of cells with 4 sets of chromosomes (usually in plants, or during certain phases of cell division). 🔄 Cell Cycle 1.​ Interphase (cell grows, copies DNA) ○​ G1: Growth ○​ S: DNA copied ○​ G2: More growth/prep for division 2.​ Mitosis: Cell divides nucleus 3.​ Cytokinesis: Cell splits into 2 🌱 Cancer ●​ Happens when the cell cycle is not controlled and cells divide uncontrollably. ✂️ Mitosis vs. Meiosis Feature Mitosis Meiosis Purpose Growth and repair Make gametes (sperm/egg) Location Somatic (body) cells Testes/Ovaries Result 2 identical cells (diploid) 4 different cells (haploid) Errors Can cause cancer Can cause birth defects or infertility, auneuploidys 🔎 Stages of Mitosis 1.​ 2.​ 3.​ 4.​ 5.​ Prophase – Chromosomes condense. Metaphase – Line up in the middle. Anaphase – Chromatids pulled apart. Telophase – New nuclei form. Cytokinesis – Cell splits. Determining Stage Length ●​ Count # of cells in each stage in microscope slide. More cells = longer time spent. Stages of Mitosis and Meiosis Mitosis and meiosis are processes of cell division, but they have different purposes and outcomes. Let’s go over what happens in each stage of mitosis and meiosis, then discuss which stages tend to be longest and shortest, and why. Mitosis (Cell Division for Growth/Repair) Purpose: To produce two identical daughter cells from a single parent cell. Occurs in somatic (body) cells. 1. Prophase (Longest Stage) ● What Happens: ○ Chromatin (loose DNA) condenses into visible chromosomes. ○ Each chromosome now has two sister chromatids (connected by a centromere). ○ The nuclear membrane starts to break down. ○ The spindle fibers (made of microtubules) begin to form from centrioles (in animal cells) or microtubule organizing centers (in plant cells). ○ Chromosomes attach to the spindle fibers. ○ Why it’s long: Prophase involves a lot of changes — DNA condensation, nuclear breakdown, and spindle formation. These processes take time. 2. Metaphase (Shortest Stage) ● What Happens: ○ Chromosomes line up along the equator (middle) of the cell. ○ Spindle fibers from the centrioles attach to the centromere of each chromosome. ○ Why it’s short: Chromosomes are already formed and just need to line up at the middle of the cell. This alignment happens quickly. 3. Anaphase ● What Happens: ○ The sister chromatids are pulled apart by the spindle fibers toward opposite sides of the cell. ○ The centromere splits, and the chromatids are now considered individual chromosomes. ○ Why it’s relatively quick: Once the chromatids start moving, they are pulled toward opposite poles rapidly. 4. Telophase (Shortest Stage) ● What Happens: ○ The separated chromosomes begin to uncoil back into chromatin. ○ New nuclear membranes form around each set of chromosomes. ○ The spindle fibers disappear. ○ Why it’s short: Telophase is mostly a process of rebuilding the nucleus, which is relatively quick.