1 Cellular Division

2 Cell Division All cells are derived from pre- existing cells All cells are derived from pre- existing cells Two new daughter cells are produced for growth and to replace damaged or old cells Two new daughter cells are produced for growth and to replace damaged or old cells Differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, & animals) Differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, & animals)

Why do cells divide? 3

***Surface Area-to-Volume Ratio Volume increases faster than surface area Puts strain on metabolic functions Nutrients and waste are not transported efficiently Larger organisms do not necessarily have bigger cells… just more of them

6 Keeping Cells Identical The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules

7 DNA Replication DNA must be copied or replicated before cell division DNA must be copied or replicated before cell division Each new cell will then have an identical copy of the DNA Each new cell will then have an identical copy of the DNA Original DNA strand Two new, identical DNA strands

8 Identical Daughter Cells Parent Cell Two identical daughter cells

9 Chromosomes

Chromosomes condense at the start of mitosis. DNA wraps around proteins (histones) that condense it. DNA double helix DNA and histones Chromatin Supercoiled DNA

12 Prokaryotic Chromosome The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane

13 Eukaryotic Chromosomes All eukaryotic cells store genetic information in chromosomes All eukaryotic cells store genetic information in chromosomes Most eukaryotes have between 10 and 50 chromosomes in their body cells Most eukaryotes have between 10 and 50 chromosomes in their body cells Human body cells have 46 chromosomes or 23 identical pairs Human body cells have 46 chromosomes or 23 identical pairs

14 Chromosomes in Dividing Cells Duplicated chromosomes are called chromatids & are held together by the centromere Called Sister Chromatids

15

16 Karyotype A picture of the chromosomes from a human cell arranged in pairs by size A picture of the chromosomes from a human cell arranged in pairs by size First 22 pairs are called autosomes First 22 pairs are called autosomes Last pair are the sex chromosomes Last pair are the sex chromosomes XX female or XY male XX female or XY male

17 Boy or Girl? Y - Chromosome X - Chromosome The Y Chromosome Decides

18 Cell Reproduction

19 Types of Cell Reproduction Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells Mitosis & binary fission are examples of asexual reproduction Mitosis & binary fission are examples of asexual reproduction Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells Meiosis is a type of sexual reproduction Meiosis is a type of sexual reproduction

20 The Cell Cycle

21 Five Phases of the Cell Cycle 1.G 1 - primary growth phase 2.S – synthesis; DNA replicated 3.G 2 - secondary growth phase collectively these 3 stages are called interphase 4.M - mitosis 5.C - cytokinesis

22 Cell Cycle

23 Interphase - G 1 Stage 1 st growth stage after cell division 1 st growth stage after cell division Cells spend the majority of time in this phase Cells spend the majority of time in this phase Cells mature by making more cytoplasm & organelles Cells mature by making more cytoplasm & organelles Cell carries on its normal metabolic activities Cell carries on its normal metabolic activities

24 Interphase – S Stage Synthesis stage Synthesis stage DNA is copied or replicated DNA is copied or replicated Two identical copies of DNA Original DNA

25 Interphase – G 2 Stage 2 nd Growth Stage 2 nd Growth Stage Occurs after DNA has been copied Occurs after DNA has been copied All cell structures needed for division (M) are made (e.g. centrioles) All cell structures needed for division (M) are made (e.g. centrioles) Both organelles & proteins are synthesized Both organelles & proteins are synthesized

26 What’s Happening in Interphase? What the cell looks like Animal Cell What’s occurring

27 Draw and Label the Cell Cycle Daughter Cells DNA Copied Cells Mature Cells prepare for Division Cell Divides into Identical cells

28 Mitosis

MICROTUBULES DIPLOID

Sister Chromatids separate DIPLOID

31 Mitosis Division of the nucleus Division of the nucleus Also called karyokinesis Also called karyokinesis Only occurs in eukaryotes Only occurs in eukaryotes Has four phases Has four phases Doesn’t occur in some cells such as brain cells Doesn’t occur in some cells such as brain cells

32 Four Mitotic Phases: PMAT Prophase Prophase Metaphase Metaphase Anaphase Anaphase Telophase Telophase

33 Early Prophase Chromatin in nucleus condenses to form visible chromosomes Chromatin in nucleus condenses to form visible chromosomes Mitotic spindle forms from fibers in cytoskeleton or centrioles (animal) Mitotic spindle forms from fibers in cytoskeleton or centrioles (animal) Chromosomes Nucleolus Cytoplasm Nuclear Membrane

34 Late Prophase Nuclear membrane & nucleolus are broken down Nuclear membrane & nucleolus are broken down Chromosomes continue condensing & are clearly visible Chromosomes continue condensing & are clearly visible Spindle fibers called kinetochores attach to the centromere of each chromosome Spindle fibers called kinetochores attach to the centromere of each chromosome Spindle finishes forming between the poles of the cell Spindle finishes forming between the poles of the cell

35 Late Prophase Nucleus & Nucleolus have disintegrated Chromosomes

36 Metaphase Chromosomes, attached to the kinetochore fibers, move to the center of the cell Chromosomes, attached to the kinetochore fibers, move to the center of the cell Chromosomes are now lined up at the equator Chromosomes are now lined up at the equator Pole of the Cell Equator of Cell

37 Metaphase Chromosomes lined at the Equator Asters at the poles Spindle Fibers

38 Metaphase Aster Chromosomes at Equator

39 Anaphase Occurs rapidly Occurs rapidly Sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers Sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers

40 Anaphase Sister Chromatids being separated

41 Telophase Sister chromatids at opposite poles Sister chromatids at opposite poles Spindle disassembles Spindle disassembles Nuclear envelope forms around each set of sister chromatids Nuclear envelope forms around each set of sister chromatids Nucleolus reappears Nucleolus reappears CYTOKINESIS occurs CYTOKINESIS occurs Chromosomes reappear as chromatin Chromosomes reappear as chromatin

42 Comparison of Anaphase & Telophase

43 Cytokinesis Cytokinesis means division of the cytoplasm Cytokinesis means division of the cytoplasm Division of cell into two, identical halves called daughter cells Division of cell into two, identical halves called daughter cells In plant cells, cell plate forms at the equator to divide cell In plant cells, cell plate forms at the equator to divide cell In animal cells, cleavage furrow forms to split cell In animal cells, cleavage furrow forms to split cell

44 Cytokinesis Cleavage furrow in animal cell Cell plate in plant cell

45 Mitotic Stages

46 Daughter Cells of Mitosis Have the same number of chromosomes as each other and as the parent cell from which they were formed Have the same number of chromosomes as each other and as the parent cell from which they were formed Identical to each other, but smaller than parent cell Identical to each other, but smaller than parent cell Must grow in size to become mature cells (G 1 of Interphase) Must grow in size to become mature cells (G 1 of Interphase)

47 Identical Daughter Cells Chromosome number the same, but cells smaller than parent cell What is the 2n or diploid number? 2

Cell Cycle - review Interphase –G1: –S: –G2: Mitosis –P: –M: –A: –T: Cytokinesis 48

49 Review of Mitosis

50 Eukaryotic Cell Division Used for growth and repair Used for growth and repair Produce two new cells identical to the original cell Produce two new cells identical to the original cell Cells are diploid (2n) Cells are diploid (2n) Chromosomes during Metaphase of mitosis ProphaseMetaphase Anaphase Telophase Cytokinesis

51 Mitosis Animation Name each stage as you see it occur?

52 Mitosis in Onion Root Tips Do you see any stages of mitosis?

53 Identify the Stages Early, Middle, & Late Prophase Late Prophase MetaphaseAnaphase Late Anaphase Telophase Telophase & Cytokinesis ? ? ?? ? ??

54 Locate the Four Mitotic Stages in Plants Metaphase Prophase Anaphase Telophase

55 Uncontrolled Mitosis If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors Oncogenes are special proteins increase the chance that a normal cell develops into a tumor cell Oncogenes are special proteins that increase the chance that a normal cell develops into a tumor cell Cancer cells