Lecture 06, 08, 09
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Questions and Answers

What is the process by which a parent cell divides into two daughter cells?

  • Mitosis (correct)
  • Cytokinesis
  • Telophase
  • Meiosis

    • When does DNA replication occur in the cell cycle?

  • Metaphase
  • Interphase (correct)
  • Prophase
  • Anaphase

    • Which type of cell division produces haploid gametes for sexual reproduction?

  • Telophase
  • Cytokinesis
  • Mitosis
  • Meiosis (correct)

    • What is the purpose of checkpoints in the cell cycle?

    <p>To detect and repair DNA damage (C)</p> Signup and view all the answers

    What happens during prophase?

    <p>Nuclear envelope breakdown, chromatin condensation, nucleolus disappearance, mitotic spindle assembly (A)</p> Signup and view all the answers

    What characterizes prometaphase?

    <p>Complete breakdown of the nuclear envelope, spindle apparatus attaching to sister chromatids' kinetochores (A)</p> Signup and view all the answers

    What occurs during metaphase?

    <p>Centromeres of chromosomes align on the metaphase plate, held by cohesins, microtubule organizing centers push and pull on centromeres (B)</p> Signup and view all the answers

    What is responsible for ensuring error-free chromosome segregation during anaphase?

    <p>Stable attachment of spindle apparatus to kinetochores on sister chromatids (D)</p> Signup and view all the answers

    What is responsible for pushing and pulling on centromeres during metaphase?

    <p>Microtubule organizing centers (MTOCs) (B)</p> Signup and view all the answers

    What is formed from two centrosomes during prophase?

    <p>Mitotic spindle begins to assemble (C)</p> Signup and view all the answers

    What is the result of meiosis?

    <p>Four haploid daughter cells (D)</p> Signup and view all the answers

    What happens in meiosis I?

    <p>Homologous chromosomes are separated (D)</p> Signup and view all the answers

    What occurs in meiosis II?

    <p>Chromatids separated and distributed like mitosis (A)</p> Signup and view all the answers

    What is the result of mitosis?

    <p>Two daughter cells with the same chromosome number as the parent cell (D)</p> Signup and view all the answers

    What is the most important checkpoint before M phase?

    <p>G2/M (B)</p> Signup and view all the answers

    What are the two DNA strands known as?

    <p>Polynucleotides (A)</p> Signup and view all the answers

    What are the nitrogenous bases of the two separate polynucleotide strands bound together by?

    <p>Hydrogen bonds (A)</p> Signup and view all the answers

    What is the sugar component of a nucleotide in DNA?

    <p>Deoxyribose (D)</p> Signup and view all the answers

    Which nitrogenous bases are classified as purines in DNA?

    <p>Adenine and guanine (C)</p> Signup and view all the answers

    What is the width of the major groove in a DNA double helix?

    <p>22 ångströms (C)</p> Signup and view all the answers

    What type of nucleobase forms hydrogen bonds to pyrimidines in DNA?

    <p>Purines (D)</p> Signup and view all the answers

    Which proteins usually make contact with the sides of the bases exposed in the major groove of DNA?

    <p>Transcription factors (C)</p> Signup and view all the answers

    Which DNA component forms the backbone by connecting adjacent sugars?

    <p>Phosphate group (A)</p> Signup and view all the answers

    What is the primary structure of DNA?

    <p>Double helix (B)</p> Signup and view all the answers

    What percentage of human DNA codes for proteins?

    <p>Less than 2% (B)</p> Signup and view all the answers

    What process uses DNA as a template to produce RNA?

    <p>Transcription (B)</p> Signup and view all the answers

    Where is prokaryotic DNA found?

    <p>In the cytoplasm in circular chromosomes (B)</p> Signup and view all the answers

    What is the term used to describe the process of producing two identical replicas of DNA from one original DNA molecule?

    <p>Replication (A)</p> Signup and view all the answers

    What is the distinctive property of the cell that makes DNA replication essential?

    <p>Division (B)</p> Signup and view all the answers

    What is the term for the process during which each strand of the original DNA molecule serves as a template for the production of its counterpart?

    <p>Replication (B)</p> Signup and view all the answers

    Where does DNA replication begin in a cell?

    <p>Origins of replication (A)</p> Signup and view all the answers

    What is the rate of DNA replication in a living cell?

    <p>749 nucleotides per second (D)</p> Signup and view all the answers

    What is the mutation rate per base pair per replication?

    <p>1.7 per 10^8 (D)</p> Signup and view all the answers

    What drives DNA polymerization?

    <p>Hydrolysis of high-energy phosphate bonds (B)</p> Signup and view all the answers

    What is the error rate of DNA polymerases?

    <p>Less than one mistake for every 10^7 nucleotides added (A)</p> Signup and view all the answers

    Which enzyme is responsible for unwinding DNA at the origin during replication?

    <p>Helicase (A)</p> Signup and view all the answers

    What type of bonds hold adenine and thymine, and guanine and cytosine together in DNA?

    <p>Hydrogen bonds (A)</p> Signup and view all the answers

    Which stage of the cell cycle does DNA replication occur?

    <p>S-stage (Synthesis) (C)</p> Signup and view all the answers

    What are the components of a nucleotide in DNA?

    <p>Sugar, phosphate, and a nucleobase (C)</p> Signup and view all the answers

    What is the directionality of DNA strands referred to as?

    <p>5' and 3' ends referring to the carbon atom in deoxyribose to which the next phosphate in the chain attaches. (D)</p> Signup and view all the answers

    Which technique is used for in vitro DNA replication?

    <p>Polymerase chain reaction (PCR) (C)</p> Signup and view all the answers

    What aids in extending existing DNA strands during replication?

    <p>Primer and DNA polymerases (B)</p> Signup and view all the answers

    Which category do most prokaryotic organisms fall into?

    <p>Unicellular and classified into bacteria and archaea (D)</p> Signup and view all the answers

    What is the oldest form of life thought to be?

    <p>Unicellular organisms (A)</p> Signup and view all the answers

    What stage of multicellular organisms serves as reproductive unicells?

    <p>Gametes (A)</p> Signup and view all the answers

    Which process allows for efficient recombinational repair of DNA damage and a greater range of genetic diversity in eukaryotes?

    <p>Meiosis (D)</p> Signup and view all the answers

    What is the distinguishing feature of ciliophora, or ciliates, a group of protists?

    <p>Cilia for locomotion (C)</p> Signup and view all the answers

    Which kingdom recognizes seven phyla including Euglenozoa, Amoebozoa, and Microsporidia?

    <p>Protozoa (C)</p> Signup and view all the answers

    Which eukaryotic organelle contains its own set of DNA and has bacteria-like ribosomes?

    <p>Mitochondria (D)</p> Signup and view all the answers

    What is the primary basis for catalyzing organic chemical reactions and self-replication, according to the RNA world hypothesis?

    <p>RNA (D)</p> Signup and view all the answers

    What distinguishes prokaryotes from eukaryotes in terms of their chromosome structure?

    <p>Prokaryotes have a single, circular chromosome (A)</p> Signup and view all the answers

    Which statement accurately describes the metabolic capability of prokaryotes?

    <p>They can utilize a wide range of organic and inorganic materials for metabolism (C)</p> Signup and view all the answers

    What is the primary role of plasmids in bacteria?

    <p>They carry genes for novel abilities, including antibiotic resistance (D)</p> Signup and view all the answers

    How are archaea different from eukaryotes at a molecular level?

    <p>They have significant molecular differences from eukaryotes, notably in their membrane structure and ribosomal RNA (C)</p> Signup and view all the answers

    In what kind of environments do archaea primarily inhabit?

    <p>Extreme environments such as thermophiles, psychrophiles, alkaliphiles, acidophiles, and piezophiles (D)</p> Signup and view all the answers

    What distinguishes methanogens among archaea?

    <p>Their ability to produce methane gas (A)</p> Signup and view all the answers

    What is a key characteristic of eukaryotic cells?

    <p>Contain membrane-bound organelles such as mitochondria, a nucleus, and chloroplasts (B)</p> Signup and view all the answers

    Study Notes

    • Cell divisions halt progression through cell cycle by inhibiting specific cyclin-CDK complexes.

    • Meiosis consists of two divisions resulting in four haploid daughter cells.

    • Homologous chromosomes are separated in meiosis I, each daughter cell receiving one copy of each chromosome.

    • Chromosomes have two sister chromatids which are separated in meiosis II.

    • Both meiosis and mitosis are present in last eukaryotic common ancestor.

    • Prokaryotes undergo binary fission or alternative manners of division, all preceded by DNA replication.

    • In eukaryotes, mitotic divisions create progeny from multicellular organisms, and enable growth and repair.

    • Mitotic cell division includes mitosis (equational division) and meiosis (reductional division).

    • Mitosis: chromosomes align on metaphase plate, then split and distributed between two daughter cells.

    • Meiosis I: homologous chromosomes paired, then separated and distributed between two daughter cells.

    • Meiosis II: chromatids separated and distributed like mitosis.

    • In humans and other animals, meiosis produces four gametes.

    • In plants, meiosis produces spores which germinate into haploid vegetative phase.

    • Interphase precedes mitosis, meiosis, and cytokinesis.

    • Interphase consists of G1, S, and G2 phases.

    • G1: cell growth, preparation for DNA replication, checkpoints for cell size and DNA damage.

    • S phase: chromosomes replicated.

    • G2: final stages of growth, checkpoints for cell size and DNA replication, spindles synthesized.

    • Mitosis or meiosis occurs in M phase.

    • Cyclin and cyclin-dependent kinases control checkpoints, progression through interphase.

    • Interphase progression results from increased cyclin and cyclin-dependent kinase attachment.

    • Three checkpoints before M phase: G1-S, G2, and metaphase.

    • Most important checkpoint is G1-S, ensuring cell is prepared for DNA replication.

    • DNA is a long polymer made of repeating nucleotide units, each consisting of a sugar, a phosphate group, and a nucleobase.

    • The sugar in DNA is 2-deoxyribose, and the backbone is formed by phosphate groups connecting the third and fifth carbon atoms of adjacent sugars.

    • DNA usually exists as a double helix, with two antiparallel strands held together by hydrogen bonds and base-stacking interactions.

    • Humans have more than 98% non-coding DNA, and the remaining coding DNA specifies the order of amino acids in proteins.

    • RNA is produced using DNA as a template in a process called transcription, and it specifies the order of amino acids in proteins through the genetic code during translation.

    • Eukaryotic DNA is organized into chromosomes, while prokaryotic DNA is found in the cytoplasm in circular chromosomes.

    • Chromatin proteins help compact and organize DNA, guiding interactions between DNA and other proteins.

    • DNA strands have asymmetric ends, with a 5′ phosphate group and a 3′ hydroxyl group, and they have a buoyant density of 1.7g/cm3.

    • The nucleobases in DNA are classified into two groups: the purines (adenine and guanine) and the pyrimidines (cytosine, thymine, and uracil).

    • Modified bases, such as 5-methylcytosine, occur in some DNA molecules, and their presence can help bacteria avoid restriction enzymes.

    • DNA replication involves the unwinding of DNA at the origin and the synthesis of new strands through the action of an enzyme called helicase.

    • Replication forks grow bi-directionally from the origin, aided by various proteins.

    • DNA polymerase synthesizes new strands by adding nucleotides that complement the template strands.

    • DNA replication occurs during the S-stage of interphase.

    • Artificial DNA replication can be performed in vitro using DNA polymerases and primers.

    • Techniques like Polymerase chain reaction (PCR), ligase chain reaction (LCR), and transcription-mediased amplification (TMA) are used for in vitro DNA replication.

    • DNA is a double-stranded molecule made up of nucleotides.

    • Nucleotides consist of a sugar, a phosphate, and a nucleobase.

    • Adenine pairs with thymine, and guanine pairs with cytosine through hydrogen bonds.

    • DNA strands have a directionality, with the 5' and 3' ends referring to the carbon atom in deoxyribose to which the next phosphate in the chain attaches.

    • DNA polymerases extend existing strands by adding new nucleotides, aided by a primer.

    • DNA polymerization is driven by the hydrolysis of high-energy phosphate bonds.

    • DNA polymerases are highly accurate, with an error rate of less than one mistake for every 107 nucleotides added.

    • Proofreading and post-replication mismatch repair mechanisms ensure replication fidelity.

    • DNA replication proceeds in three steps: initiation, elongation, and termination.

    • The rate of DNA replication in a living cell is approximately 749 nucleotides per second.

    • The mutation rate per base pair per replication is 1.7 per 108.

    • The RNA world hypothesis suggests that early RNA molecules were the basis for catalyzing organic chemical reactions and self-replication.

    • Compartmentalization was necessary for chemical reactions to occur effectively and to differentiate reactions with the external environment.

    • Ribocells or ribocytes are hypothetical cells with RNA genomes instead of DNA, which may have been the earliest form of life.

    • Prokaryotes lack membrane-bound organelles and have a single, circular chromosome.

    • Prokaryotes have the ability to utilize a wide range of organic and inorganic materials for metabolism.

    • Bacteria are one of the oldest forms of life and can reproduce asexually through binary fission or sexually through natural genetic transformation.

    • Plasmids are circular, self-replicating DNA molecules that carry genes for novel abilities, including antibiotic resistance.

    • Photosynthetic cyanobacteria are the most successful bacteria and changed the early Earth's atmosphere by oxygenating it, leaving behind extensive fossil records in the form of stromatolites.

    • Archaea are phylogenetically related to eukaryotes and have significant molecular differences, most notably in their membrane structure and ribosomal RNA.

    • Archaea inhabit extreme environments and can be classified as thermophiles, psychrophiles, alkaliphiles, acidophiles, and piezophiles.

    • Methanogens are a subset of archaea that can produce methane and are significant in wetland environments as well as in the digestive systems of animals.

    • Eukaryotic cells contain membrane-bound organelles, such as mitochondria, a nucleus, and chloroplasts.

    • Prokaryotic cells may have transitioned into eukaryotic cells between 2 and 2.5 billion years ago.

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    Lecture 06 Prokaryotes and Eukaryotes Lecture 08 Cell Division Structure of DNA and DNA replication Lecture 09 Cell Division Mitosis and Meisosis

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