Lect 4 Notes Cell Cycle & Meiosis PDF

2023-09-28 CELL CYCLE AND MEIOSIS Chapters 6 and 7 (a little from ch 4 & 18) 1 BioA11 Introduction to the Biology of Humans • COURSE OBJECTIVES: INTRO Instructor: Karen Williams, PhD Office: SY210A Office hours: virtual::Thursday 11301200h ; in-person: Friday 1600h-1630h, or by appointment Ema...

2023-09-28 CELL CYCLE AND MEIOSIS Chapters 6 and 7 (a little from ch 4 & 18) 1 BioA11 Introduction to the Biology of Humans • COURSE OBJECTIVES: INTRO Instructor: Karen Williams, PhD Office: SY210A Office hours: virtual::Thursday 11301200h ; in-person: Friday 1600h-1630h, or by appointment Email: [email protected] • • • _______________ _______________ _______________ • See syllabus • Aim for this week: • 4. To understand the importance of cells and cell divisions, and to understand how to cite information sources 2 1 2023-09-28 BioA11 Introduction to the Biology of Humans Lecture Week 4: Cell cycle & Meiosis • Cell cycle: • Meiosis: • What are the • What is meiosis and components of cells? • How do cells divide, interact and die? • How are gametes produced? when does it occur? • What are critical periods for development? 3 BioA11 Introduction to the Biology of Humans What are the components of cells? https://flic.kr/p/DU5VDY • Labels A. ___________ B. ___________ C. ____________ A B https://flic.kr/p/Y1zvqn C 4 2 2023-09-28 BioA11 Introduction to the Biology of Humans How was the source cited on the slide? • Photo _____________ • __________________ • __________________ 5 © 2016 Pearson Education, Inc. Cells divide • Normal cells must divide: • To grow • To replace dead/damaged cells • To reproduce • Sexual and asexual reproduction Asexual reproduction -only one parent -offspring are genetically identical to parent Sexual reproduction -requires genetic information from two parents -gametes from two parents combine to form a new organism (offspring) -offspring are genetically different from one another and from the parents http://images.slideplayer.com/7/1728365/slides/slide_2.jpg 6 3 2023-09-28 © 2016 Pearson Education, Inc. DNA must be copied before cells divide DNA is the genetic material • Must be copied before cells divide • for both sexual and asexual reproduction • DNA carries genes • Genes: section of DNA with instructions for building all of the cell’s proteins https://passel.unl.edu/Image/siteImages/ChromgendnaLG.jpg 7 © 2016 Pearson Education, Inc. DNA in cells is organized into chromosomes Chromosomes: made of DNA wrapped around proteins • Normally, in uncondensed, string-like form • Become condensed prior to cell division • Carry hundreds of genes • Sister chromatids: duplicated chromosomes, attached at the centromere 8 4 2023-09-28 © 2016 Pearson Education, Inc. 6.2 Passing Genes and Chromosomes to Daughter Cells 9 https://upload.wikimedia.org/wikipedia/en/b/bf/Chromarms.gif http://docs.clinicaltools.com/images/webpage/larasig/moduleimgs/chrome17.jpg 10 5 2023-09-28 © 2016 Pearson Education, Inc. https://passel.unl.edu/Image/siteImages/ChromgendnaLG.jpg 11 © 2016 Pearson Education, Inc. DNA replication Duplicated chromosomes = duplicated DNA 12 6 2023-09-28 © 2016 Pearson Education, Inc. DNA replication DNA Structure: double-stranded “twisted ladder” • Sides of the ladder: sugar-phosphate backbone • “Rungs” of the ladder: nitrogen bases connected by hydrogen bonds • Adenine (A) pairs with thymine (T) • Cytosine (C) pairs with guanine (G) 13 © 2016 Pearson Education, Inc. DNA replication • Occurs before cell division • Begins by splitting helix in half (up the middle) • Semiconservative replication • Newly formed DNA strand has one-half new daughter DNA and one-half conserved parental DNA. 14 7 2023-09-28 © 2016 Pearson Education, Inc. DNA replication DNA polymerase: the enzyme that replicates DNA • Moves along the unwound DNA to form the new strands -base pairing dictates the order of nucleotides that are added by polymerase -can make mistakes = mutations 15 © 2016 Pearson Education, Inc. Cell division by Mitosis - Asexual division that produces 2 identical daughter cells (also identical to the original parent cell) - occurs in all cells of the body that are not germ cells. Germ cells produce eggs and sperm. -In cells that divide by mitosis, the cell cycle has three steps: 1. Interphase: DNA replicates 2. Mitosis: copied chromosomes are moved into daughter cells 3. Cytokinesis: parent cell splits into two daughter cells 16 8 2023-09-28 © 2016 Pearson Education, Inc. 6.3 The Cell Cycle and Mitosis Most of the cell cycle is spent in interphase. Interphase has three phases: • G1: cell grows, organelles duplicate • S: DNA replicates • G2: cell makes proteins needed to complete mitosis 17 © 2016 Pearson Education, Inc. 6.3 The Cell Cycle and Mitosis Mitosis: movement of chromosomes from original eukaryotic parent cell into two genetically identical daughter cells -sister chromatids are pulled apart and placed in each daughter cell http://www.yourgenome.org/sites/default/files/illustrations/process/mitosis_yourgenome.png 18 9 2023-09-28 © 2016 Pearson Education, Inc. 6.3 The Cell Cycle and Mitosis • Mitosis can be divided into four stages: • Prophase • Metaphase • Anaphase • Telophase http://legacy.hopkinsville.kctcs.edu/instructors/Jason-Arnold/VLI/Module%202/m2celldivision/f803_the_cell_cycle-_c.jpg 19 © 2016 Pearson Education, Inc. 6.3 The Cell Cycle and Mitosis 20 10 2023-09-28 © 2016 Pearson Education, Inc. 6.3 The Cell Cycle and Mitosis 21 © 2016 Pearson Education, Inc. 6.3 The Cell Cycle and Mitosis Cytokinesis: division of the cytoplasm • Occurs after telophase of mitosis • Cell is split into two daughter cells • Cells then reenter interphase • Animals: • Proteins pinch the original cell into two new cells 22 11 2023-09-28 BioA11 Introduction to the Biology of Humans Describe the stage of mitosis shown (arrow)? https://flic.kr/p/DU5VDY • Stage of cell division in cell indicated by arrow is • __________________ https://flic.kr/p/Y1zvqn 23 © 2016 Pearson Education, Inc. 6.3 The Cell Cycle and Mitosis The cell cycle is tightly regulated -prevents tumour formation -cells with defective cell cycle regulation are destroyed 24 12 2023-09-28 © 2016 Pearson Education, Inc. 6.4 Cell Cycle Control Tumor suppressors: proteins that are continuously surveying cells to check for any abnormalities that could lead to unregulated growth • e.g. inspect newly replicated DNA • Damaged cells do not continue with cell division 25 © 2016 Pearson Education, Inc. 6.4 Cell Cycle Control Mutations tumor-suppressor genes • normal to BRCA1 gene encodes a tumor Tumor suppressor Mutation suppressor Mutated tumor suppressor Mutation DNA Protein Tumor-suppressor protein stops tumor formation by suppressing cell division. Mutated tumorsuppressor protein fails to stop tumor growth. Figure 6.11 26 13 2023-09-28 © 2016 Pearson Education, Inc. 6.4 Cell Cycle Control • Normal cells halt at checkpoints after every major event in the cell cycle. • Proteins determine condition of the cell = encoded by cell cycle control genes or proto-oncogenes • Cell must pass the checkpoints to proceed with cell division. • Three checkpoints: • G1 • G2 • Metaphase 27 © 2016 Pearson Education, Inc. 6.4 Cell Cycle Control and Mutation 28 14 2023-09-28 © 2016 Pearson Education, Inc. 6.4 Cell Cycle Control Proto-oncogenes: genes that code for the cell cycle control proteins • When conditions are right, they stimulate cell growth • Oncogenes: formed from mutated proto-oncogenes • Proteins no longer regulate cell division properly • Usually over stimulate cell division, when they should not 29 © 2016 Pearson Education, Inc. 6.4 Cell Cycle Control Proto-oncogenes: genes that code for the cell cycle control proteins • When conditions are right, they stimulate cell growth Tumor suppressors: proteins that are continuously surveying cells to check for any abnormalities that could lead to unregulated growth • e.g. inspect newly replicated DNA • Damaged cells do not continue with cell division Proto-oncogenes and tumour suppressors work together to only allow healthy cells to proceed through cell division. 30 15 2023-09-28 BioA11 Introduction to the Biology of Humans Mitosis Meiosis • Daughter cell is identical • Parent cell (2n) produces to parent cell • A 2n cell gives two (2n) daughter cells 4 gametes (n) • Forms new combinations of chromosomes in gametes • New combinations of chromosomes (recombinant chromosomes) are formed during crossingover 31 © 2016 Pearson Education, Inc. A predisposition to cancer • Most of us will inherit very few, if any, mutant cell cycle control genes from parents • Mutations in those genes will be dictated by our exposure to environmental risk factors • Some individuals will inherit genes that increase their risk and their children’s risk of cancer • “runs in families” • How does that work? - Need to understand meiosis, the type of cell division that produces sperm and eggs and controls how genes are passed on from parents to offspring 32 16 2023-09-28 BioA11 Introduction to the Biology of Humans • What happened inside the chicken to produce these eggs? • ____________________ ____________________ ____________________ ____________________ https://flic.kr/p/9y8KYf 33 © 2016 Pearson Education, Inc. 6.6 Meiosis Meiosis • Specialized form of cell division in gonads (ovaries or testes) to produce gametes (eggs or sperm) • Reduces number of chromosomes in each cell by one-half • • • Human somatic cells = 46 chromosomes = diploid Human gametes = 23 chromosomes = haploid Fusion of sperm + egg = 46 chromosomes in zygote = diploid 34 17 2023-09-28 © 2016 Pearson Education, Inc. Chromosomes in somatic cells and gametes • Chromosomes come in homologous pairs • 1 from mom and 1 from dad • Note that each member of the homologous pair carry different versions of genes = alleles • After meiosis, the gametes (sperm or eggs) formed gets one of each pair 35 Somatic cells Gametes http://study.com/cimages/multimages/16/diploid-vs-haploid.jpg 36 18 2023-09-28 © 2016 Pearson Education, Inc. 6.6 Meiosis Karyotype: a photograph of chromosomes arranged in pairs (homologous pairs) • Human somatic cells have 22 pairs of autosomes and one pair of sex chromosomes = 23 pairs = 46 chromosomes = diploid 37 © 2016 Pearson Education, Inc. 6.6 Meiosis Meiosis • DNA is duplicated during interphase • Meiosis takes place in two stages • Meiosis I • Separating out the homologous pairs into two separate cells • Meiosis II • Separating out the sister chromatids in each cell to produce four haploid cells. 38 19 2023-09-28 © 2016 Pearson Education, Inc. 6.6 Meiosis I NOTE: chromosomes line up as homologous pairs 39 © 2016 Pearson Education, Inc. 6.6 Meiosis II 40 20 2023-09-28 © 2016 Pearson Education, Inc. 6.6 Meiosis Crossing over: exchange of genetic information between homologous chromosomes • Occurs during prophase I of meiosis I • Results in new types of gametes 41 © 2016 Pearson Education, Inc. 6.6 Meiosis Crossing over: exchange of genetic information between homologous chromosomes • Occurs during prophase I of meiosis I • Results in new types of gametes 42 21 2023-09-28 © 2016 Pearson Education, Inc. 6.6 Meiosis • Random alignment: the random arrangement and separation of different pairs of chromosomes during meiosis I • Results in genetically distinct gametes 43 © 2016 Pearson Education, Inc. 6.6 Meiosis Random alignment and crossing over allow a single individual to give rise to very many different type of gametes. = increases the variation in individuals that are produced when the gametes fuse. 44 22 2023-09-28 © 2016 Pearson Education, Inc. 6.6 Comparison of Mitosis and Meiosis 45 BioA11 Introduction to the Biology of Humans Development: • Critical periods: • _____________________ _____________________ • Ch.23.2 • Impact of the environment during critical periods of development can change _________ • Teratogens: chemicals, drugs and even some nutrients that cause birth defects • Case: • If you wanted to know whether exposure to a chemical caused a change in development, how could you do the study? • How would the study be done? • Discuss the results of a case • How would you answer the question for the case? • Compare exposure (FWI) with no exposure (WI) to pesticide 46 23 2023-09-28 BioA11 Introduction to the Biology of Humans Case: Does exposure to a pesticide in FWI affect the gestation time? Effect of FWI exposure to Chlordecone 38.6 * Mean time of gestation (weeks) 38.5 38.4 38.3 38.2 38.1 38 37.9 FWI (French West Indies) WI (other Caribbean) Exposure to Chlordecone pesticide during pregnancy Data modified from Kadhel et al. 2014 American Journal or Epidemiology 179(5) 536-544 47 BioA11 Introduction to the Biology of Humans Stem cells relate to tissue and organ transplantation because ___ • How do stem cells relate to tissues and organ donation? • Video: • https://youtu.be/wHGV2ofl9s0 • A stem cell is _____________ • Stem cells can_________________ differentiated cells • See Chapter 10 section 10.3; and Chapter 18 section 18.2 • How would you reference the textbook? • To reference the video put the title _______; then the URL. 48 24 2023-09-28 FIGURE 18.9 Muscle cells Epithelial cells Cells seeded on scaffold Bladder scaffold Tissue engineered bladder 49 What are tissues? What are organs? • Tissues are: ______________ • The basic types of tissues in the human body include • _____________ • ______________ • ______________ • ______________ • Organs are __________________________ • How many major organ systems are there in the human body? ___ • (see Ch 18 section 18.2) 50 25 2023-09-28 © 2016 Pearson Education, Inc. 17.1 Tissue Donation Four basic types of tissue in the human body: • Epithelial – skin transplants for burn victims are now well developed, cornea transplants are possible • Connective – blood and bone marrow can be transplanted from live donors • Muscle – cardiac muscle tissue can be transplanted as long as it is within 4 hours after removal from the donor’s body • Nervous – least likely to be involved in a transplant 51 FIGURE 18.6 Muscle cell Muscle tissue Heart organ Circulatory system Organism 52 26 2023-09-28 © 2016 Pearson Education, Inc. 17.2 Organs and Organ Systems Organs: structures composed of two or more tissue types working together for a specific function • Organs that interact to perform a common function form an organ system • 11 major organ systems in the human body • All of the organ systems of a body work together to help an organism function. 53 TABLE 18.1 54 27 2023-09-28 BioA11 Introduction to the Biology of Humans How were sources cited in the presentation? Photos were cited on the slides below the figure where it was used Journal articles were cited on the slides where the information was used Video should be cited by title and URL 55 BioA11 Introduction to the Biology of Humans Lecture Week 4 • Cell cycle: • Meiosis: • What are the • What is meiosis and components of cells? • How do cells divide, interact and die? • Stem cells are (see ch 10.3) __________ • How are gametes produced? • Gametes are ____ when does it occur? • Meiosis is _________ • What are critical periods for development? • See chapter 23.2 Toxic Stress for more information 56 28