CELL CYCLE, DNA REPLICATION AND MITOSIS
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CELL CYCLE, DNA REPLICATION AND MITOSIS Reasons why cells
divide: 1. Repair 2. Replace old or damage cells 3.
Reproduction
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Cellular Growth Copyright McGraw-Hill Education Cell Size
Limitations Ratio of surface area to volume Smaller cells can
transport substances more easily Diffusion is inefficient over
longer distances Cytoskeleton less efficient when cells are larger
Cellular communication more efficient in smaller cells
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Cellular Growth Copyright McGraw-Hill Education The Cell Cycle
Once a cell reaches its size limit it must either stop growing or
divide. Cells reproduce by a cycle of growing and dividing called
the cell cycle. Each time a cell goes through one complete cycle,
it becomes two cells. Three main stages of the cell cycle:
Interphase: stage during which the cells grows, carries out
cellular functions, and replicates its DNA. Mitosis: the cells
nucleus and nuclear material divide; has four substages.
Cytokinesis: cells cytoplasm divides, creating two new cells.
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CELL CYCLE IS THE SERIES OF EVENTS THAT TAKE PLACE IN A CELL
LEADING TO ITS DIVISION AND DUPLICATION (REPLICATION) THAT PRODUCES
TWO DAUGHTER CELLS. IN CELLS WITHOUT A NUCLEUS (PROKARYOTIC), THE
CELL CYCLE OCCURS VIA A PROCESS TERMED BINARY
FISSION.CELLPROKARYOTICBINARY FISSION G0G0
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Many different Diagrams
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CELL CYCLE The sequence of growth and division of a cell An
average cycle may be 22 hours Two general periods: 1. growth phase
2. division phase
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INTERPHASE (GROWTH PHASE) Most of the cells life is spent in
interphase Longest phase (90% of cells growth) Centrioles help to
organize cell division Chromatin DNA bound protein within the
nucleus
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INTERPHASE (GROWTH PHASE) G 1 1 st period of growth 1. Increase
in size. 2. Makes new proteins and organelles. G 0 Resting Phase 1.
If cells dont go into this phase it could cause cancer (tumor) S
DNA is synthesized or replicated 1. Chromosomes are replicated. 2.
New DNA molecules are made. G 2 final cell growth 1. Shortest phase
2. Prepares cell for mitosis New DNA is formed during 4
phases:
AFTER CELL GROWTH (G 1 ) AND RESTING STAGE (G 0 ): THE CELL
WILL ENTER INTO THE: DNA REPLICATION STAGE (S)
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1.What is the name of this monomer? 2.What is the name of the
polymer or macromolecule to which this monomer belongs? REVISIT
PRI0R KNOWLEDGE
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FIRST LETS LOOK AT THE HISTORY OF DNA Alfred Hershey &
Martha Chase (1952) Oswald Avery (1944) Erwin Chargaff (1950)
Rosalind Franklin (1952) James Watson & Francis Crick
(1953)
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WHERE HAVE SCIENTISTS BEEN? A BRIEF HISTORY Oswald Avery (1944)
Discovered that the nucleic acid DNA stores and transmits the
genetic information from one generation of an organism to the
next
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ALFRED HERSHEY & MARTHA CHASE (1952) Concluded that the
genetic material of the bacteriophage was DNA, not protein. Used
radioactive phosphorous and sulfur.
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ERWIN CHARGAFF (1950) Discovered a relationship in the
nitrogenous bases Adenine (A) = Thymine (T) Guanine (G) = Cytosine
(C)
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ROSALIND FRANKLIN (1952) Took an x-ray of the DNA structure so
the patterns could be seen. The x-rays show that DNA is twisted
around each other like a helix and has two strands.
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JAMES WATSON & FRANCIS CRICK (1953) Studied the structure
of DNA by building a 3- dimentional model of the molecule after
using clues from Franklins x-ray of DNA.
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Watson and Crick proposed that DNA is made up of 2 chains of
nucleotides held together by nitrogenous bases & that the 2
strands are twisted together in a shape called a double helix.
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DNA REPLICATION: AMOEBA SISTERS
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THE STRUCTURE OF DNA DNA is a polymer made up of repeating
monomers of nucleotides. DNA determines an organisms traits by
controlling the manufacturing of proteins. The sequencing of
nucleotides forms unique genetic information.
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OVERVIEW OF DNA
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The nucleus of a cell contains chromosomes
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Which are made up of coiled DNA
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Eukaryotic chromosomes contain DNA wrapped around proteins
called Histones. Chromosome Solenoid Histone Proteins DNA Double
Helix
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Each strand of DNA is made up of subunits called
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Each nucleotide is constructed of 3 parts: a PHOSPHATE group, a
SUGAR molecule & 1 of 4 nitrogen bases Adenine (A) Guanine (G)
Cytosine (C) Thymine (T) Purines Pyrimidines
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DNA REPLICATION Copying process by which a cell duplicates its
DNA DNA molecule separates into two strands, then produces two new
complementary strands following the rules of base pairing Each
strand of the double helix of DNA serves as a template for the new
strand
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HOW REPLICATIO N OCCURS Enzyme (Helicase) unzips DNA by
breaking the hydrogen bonds between the base pairs, which produces
two replication forks DNA polymerase Joins individual nucleotides
to make a new strand Proofreads each new strand
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DNA REPLICATION
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Because of the hydrogen bonds, Adenine can only bond with
Thymine & Guanine can only bond with Cytosine *A purine is
always paired with a pyrimidine. Thymine Adenine Cytosine
Guanine
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This is known as COMPLEMENTARY base pairing
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For example: GCA ATC TA CGT TAG AT Now you try: CCA GAT TGA GGT
CTA ACT
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G 2 PHASE G 2 final cell growth 1. Shortest phase 2. Prepares
cell for mitosis 3. Check for no mistakes in the chromosomes 4.
Repairs any Mistakes
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MITOSIS
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OCCURRENCES DURING THE CELL CYCLE Cell grows. Cell prepares for
division. Cell divides to form two daughter cells. MITOSIS: The
Making of Body Cells (Somatic Cells)
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Centromere Chromatid
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TERMS TO KNOW Chromosome contains genetic information (DNA)
passed from one generation to the next Spindle microtubule that
helps separate chromosomes A Centromere: center of chromosome B
Chromatids: two identical sister parts of the chromosome
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MITOSIS (DIVISION PHASE OF BODY CELLS) 4 Phases: (PMAT)
1)Prophase 2)Metaphase 3)Anaphase 4)Telophase
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Mitosis Mnemonic & Hand Motions Handout papers
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MITOSIS ACRONYM Mitosis only Passed (prophase) My (metaphase)
Algebra (anaphase) Test (telophase) All cell cycle I (interphase)
Passed (prophase) My (metaphase) Algebra (anaphase) Test
(telophase) Corrections (cytokinesis)
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Interphase
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Prophase
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Metaphase
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Anaphase
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Telophase
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Cytokinesis
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InterphaseProphaseMetaphase
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Anaphase Telophase Cytokinesis
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4 phases that blend from one to another.
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PROPHASE 1 st and longest phase of mitosis Chromatin condenses
into chromosomes (chromosomes become visible) Nuclear envelope
disappears Centrioles migrate to poles Spindles are formed
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METAPHASE 2 nd phase of mitosis Chromosomes meet in the middle
of cell Pulled by spindles Each chromosome is attached to top of
spindle
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ANAPHASE 3 rd phase of mitosis Centromeres are split apart
Chromatids are pulled apart and begin to drift to opposite
poles
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TELOPHASE Final phase of mitosis Begins when chromatids reach
poles New nucleus starts to form Chromosomes start to unwind
Spindles disappear Cytoplasm begins to divide; cell plate
forms
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CYTOKINESIS Cytoplasm pinches completely in half Cell plate
becomes cell wall (if present) Each daughter cell has an identical
set of chromosomes
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CYTOKINESIS Animal cells The cell membrane is drawn inward
forming a cleavage furrow until the cytoplasm is pinched into 2
nearly equal parts Plant cells A cell plate gradually develops into
a separating membrane.
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OVERVIEW OF MITOSIS Interphase Prophase
MetaphaseAnaphaseTelophase Please Make Another Two Cells
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IDENTIFY THE STAGES Early, Middle, & Late Prophase Late
Prophase MetaphaseAnaphase Late Anaphase Telophase Telophase &
Cytokinesis ? ? ?? ? ??
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LOCATE THE FOUR MITOTIC STAGES IN PLANTS Metaphase Prophase
Anaphase Telophase
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CELL CYCLE AND CANCER
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CANCER Cancer is a disorder where the cell has uncontrolled
growth. (Does not go into the G 0 phase Cancer cells do NOT respond
to regulators that control timing of cell cycle (cyclins). This
causes the cells to form masses called tumors, which can damage
surrounding tissues. Growing out of control, cancer cells produce
malignant tumors Cancer cells do not respond normally to the cell
cycle control system Divide excessively Can invade other tissues
May kill the organism
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If an abnormal cell avoids destruction by the immune system, it
may form a tumor Benign: abnormal cells remain at original site
Malignant: abnormal cells can spread to other tissues and parts of
the body Metastasis: spread of cancer cells through the circulatory
system Cancers are named according to location of origin Carcinoma:
external or internal body coverings Sarcoma: tissues that support
the body Leukemia and lymphoma: blood-forming tissues Radiation and
chemotherapy are effective as cancer treatments because they
interfere with cell division
