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Cellular Reproduction Chapter 9. Limits of Cell Growth: The larger the cell, the more difficult it is for materials to enter and leave it. Rates of Cell.

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Presentation on theme: "Cellular Reproduction Chapter 9. Limits of Cell Growth: The larger the cell, the more difficult it is for materials to enter and leave it. Rates of Cell."— Presentation transcript:

1 Cellular Reproduction Chapter 9

2 Limits of Cell Growth: The larger the cell, the more difficult it is for materials to enter and leave it. Rates of Cell Growth: E. coli can double its volume in = 30 minutes. In one day, a single cell would grow into a 14 kg mass of bacteria. In 3 days = mass of the earth

3 Controls on Cell Growth: cells of the heart and nervous system rarely grow. Cells of the skin and digestive tract grow and divide rapidly throughout Life; old, worn out, and damaged cells. Cells will grow until they come into contact with each other. Uncontrolled Cell Growth: Cancer cells grow out of control until they have used up all of their nutrients

4 Chromosomes: Made up of chromatin (DNA and protein) Chromosomes: Made up of chromatin (DNA and protein) Total length of DNA is = 10,000 x length of the chromosome. Total length of DNA is = 10,000 x length of the chromosome. In 1973, Don and Ada Olins and Christopher Woodcock discovered the chromosome’s DNA was coiled around special proteins called histones. In 1973, Don and Ada Olins and Christopher Woodcock discovered the chromosome’s DNA was coiled around special proteins called histones. DNA and histone molecules form beadlike structures called nucleosomes. DNA and histone molecules form beadlike structures called nucleosomes. Nucleosomes form a thick fiber, shortened by a system of loops and coils. Nucleosomes form a thick fiber, shortened by a system of loops and coils.

5 Chromosome Structure   Composed of 2 sister chromatids and a centromere.

6 Binary Fission of a Prokaryote

7 The Cell Cycle   Is the period from the beginning of one mitosis to the beginning of the next   Consists of interphase and M phase

8 Prophase Metaphase Anaphase Telophase Interphase

9 Controls On The Cell Cycle

10 Interphase

11 Interphase  Is a period of intense activity  Proteins are made  DNA copied  ATP is made and utilized  Nucleus is synthesizing mRNA to direct cellular activities

12 Interphase   Consists of G 1, S, and G 2   Cells do not move through the cycle at the same rate   G 1 consists of cell growth and development; increase in supply of proteins, and synthesis of some organelles   S stands for synthesis: DNA replication occurs here   G 2 synthesis of more organelles and the cell prepares for mitosis (shortest of the phases)

13 Mitosis  Division of the nucleus  Occurs in somatic or body cells body cells  Can last from a few minutes to several minutes to several days days

14 Mitosis Diagram

15 Prophase (longest phase)  Chromosomes become visible as they shorten and thicken  Disintegration of the nucleolus and the nuclear envelope  Centrioles move apart  Formation of the mitotic spindle fibers  Takes up about 50-60% of mitosis

16 Metaphase (shortest phase)  Centrioles have reached the opposite poles  Chromosomes line up along the equator or middle of the cell  Centromere of each chromosome is attached to a spindle fiber

17 Anaphase (3 rd phase)  Centromeres split  Spindle fibers draw chromatids to poles of cells  Chromatids are now individual chromosomes

18 Telophase  Chromosomes have reached opposite poles  Chromosomes uncoil and become less distinct  Nuclear membrane begins to reform around chromosomes  Spindle begins to break apart  Nucleolus reappears  Cells begin to divide by formation of cell plate in plant cells and cleavage furrow in animal cells  Formation of two new daughter cells

19 Telophase (final phase)

20 Cytokinesis  Division of the cytoplasm  Occurs at the end of telophase  Results in two identical daughter cells

21 Review of Mitotic Stages

22 Meiosis  The process of gamete formation in which the chromosome number is reduced to half the normal number  Requires two nuclear divisions called Meiosis I and Meiosis II

23 Meiosis I  Interphase-the cell replicates its chromosomes  Prophase I-each pair of homologous chromosomes comes together to form a four-part structure called tetrad  Crossing Over-homologous chromosomes exchange genetic material  Metaphase I-homologous chromosomes line up in tetrads independently of each other  Anaphase I-centromeres do not split, this ensures that each new cell will receive only one chromosome from each homologous pair  Telophase I-each new cell has one half of the genetic information

24 Crossing over Pairing of homologous chromosomes Chiasma formation Chromosomes Breakage and joining Recombinant chromosomes

25 Crossing Over Animated  d2.gif

26 Metaphase I Anaphase I Telophase I Prophase II Prophase I

27 Meiosis II Prophase II Metaphase II Anaphase II Telophase II

28 Result of Meiosis 4 Haploid cells Gametes

29 Meiosis begins by replicating the chromosomes

30 Centromeres Do Not Split at Meiosis I

31 Centromeres Split at Meiosis II

32 Oogenesis  Process by which egg cells are made  Results in four haploid gametes  One functional ovum capable of fertilization  Three polar bodies disintegrate

33 Spermatogenesis  Process by which sperm cells are produced  Results in four functional sperm cells

34 2n 1 cell division: 2 daughter cells 2 cell divisions: 4 product of meiosis 2n n n n n n=chromosome number Somatic cells Cells in sexual cycle MITOSISMEIOSIS

35 Final result Mitosis : two genetically identical diploid cells from one diploid parent cell Mitosis Conservative process: Daughter cells genotypes identical to parental genotypes  Diploid organism: two sets of chromosomes (one from each parent); 2n from each parent); 2n

36   Meiosis :   Four genetically different haploid cells; from one diploid parent cell Meiosis Promotes variation among the product of meiosis (crossing over)  Haploid organism: one set of chromosomes; n

37 Mitosis vs Meiosis   Alike   Both have the stages PMAT   Both go through Cytokinesis   Both divide and make daughter cells   Both are a form of reproduction   Both take place inside the cell   Chromosomes duplicate and DNA replication occurs in each process Different   Mitosis produces two identical daughter cell, meiosis produces four genetically different cells   Crossing over and tetrad formation (synapsis) occur in prophase I of Meiosis   The centromeres split in Anaphase II   Mitosis has one division, Meiosis has two   Mitosis occurs in somatic or body cells   Meiosis occurs in reproductive organs; producing gametes   Mitosis is asexual reproduction   Meiosis ensures sexual reproduction


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