Cell division requires DNA replication Before cells can divide DNA must be

Cell division requires dna replication before cells

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Cell division requires DNA replication Before cells can divide, DNA must be replicated! One identical copy of mother cell’s genes to both daughters produced They each need the genetic code (DNA) to make their proteins later in life
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Why do cells divide? Body growth, development Tissue repair Some divide often: skin, intestines Some divide slowly: liver Some don’t divide: nervous, muscle (skeletal and cardiac) Cell cycle phases Interphase: cell division prep G 1 (→G 0 ) S- phase… make DNA copy G 2 M phase: division Mitosis: nuclear Cytokinesis: cytoplasm The cell cycle
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DNA polymerase makes new polymer by complementary base pairing Covalently binds free nucleotides from nucleoplasm Only adds nucleotides in 1 direction, produces 1. Continuous leading strand 2. Discontinous lagging strand - Okasaki fragments DNA ligase: connects Okasaki fragments Enzymes needed!! DNA helicase unwinds, separates DNA strands from histones DNA replication begins at replication fork Old strands= templates DNA replication in S-phase
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DNA replication DNA replication Two identical DNA molecules formed from original DNA Semi-conservative replication : 1 old and 1 new strand/ final DNA molecule New DNA rewinds around histone proteins Important that new DNA is not damaged or broken!
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Mitosis After G 2 Separates the duplicated DNA into two identical nuclei Daughter cells have same DNA as mother Phases: PMAT Prophase Metaphase Anaphase Telophase Self-study
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Mitosis and cytokinesis Cleavage furrow: actin microfilaments in contractile ring Self-study
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Cell destiny 1. To remain alive and function without dividing 2. To grow and divide 3. To die Killed by harmful agents or mechanical damage Self-destruct via apoptosis programmed cell death, cell self-implodes, no mess made In normal adult tissue= balance between cell division and cell loss/destruction Fates of new daughters…… Self-study
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Normal cell division Depends on: Cell cycle checkpoints and integrity of DNA Many chemicals: growth factors and regulatory and repair proteins Telomere shortening leads to aging Genes : balance between stimulating and inhibiting cell division Proto-oncogenes : favor cell division Repressor genes: (i.e. p53) inhibit cell division Mutations? Self-study
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Abnormal cell division/growth Tumors : cells fail to follow cell cycle rules, - uncontrolled cell division Benign tumor: have capsule, confined to original location, surgically remove Malignant tumor (cancer): no capsule, invade surrounding tissue, Metastasis : malignant cells break off and travel to distant tissue Self-study
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Chapter 3 Part II Protein synthesis DNA is needed to make proteins!
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Overview: From DNA to protein DNA directs its own replication (we just saw that!) DNA directs protein synthesis (we will see this now!) DNA : genetic instructions Gene : segments of DNA code for RNA protein DNA → mRNA ( transcription ) Nucleus mRNA → protein ( translation ) Cytoplasm, ribosomes
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Let’s start with the BIG picture!!!
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