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Cell Growth and Reproduction Mitosis and Meiosis

Cell Growth and Reproduction Mitosis and Meiosis. Surface area to Volume Ratio. A cell is 2mm x 2mm x 2mm What is its surface area? What is its volume?. Surface area: 2*2*6= 24mm2. Volume 2*2*2= 8mm3. Surface area :Volume Ratio 24:8 = 3:1.

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Cell Growth and Reproduction Mitosis and Meiosis

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  1. Cell Growth and ReproductionMitosis and Meiosis

  2. Surface area to Volume Ratio

  3. A cell is 2mm x 2mm x 2mm What is its surface area?What is its volume? • Surface area: • 2*2*6= 24mm2 • Volume • 2*2*2= 8mm3 • Surface area :Volume Ratio • 24:8 = 3:1

  4. What happens to the ratio of SA:V as the cell gets larger? • Having a large surface area to volume ratio allows materials to diffuse easily • Cells don’t get poisoned by their own waste • Motor proteins don’t have to pull substances as far

  5. The Cell Cycle • What happens to a cell when it reaches it size limit? • It can stop growing • It can divide • 3 Main steps to the Cell Cycle • Interphase • Mitosis • Cytokinesis

  6. The Cell Cycle

  7. Interphase • Longest Phase • 3 Stages • (G1) Performs normal function • (S) Copies DNA • (G2) Prepares to divide

  8. Interphase • G1 • Performs normal functions • Prepares to copy DNA • S • DNA replicates • DNA can be packaged in two ways: • Chromatin- unwound, loosely packed • Ponytail • Chromosome- wound, tightly packed • Braid • G2 • Cell prepares to divide its nucleus

  9. Mitosis and Cytokinesis • Why do cell need to reproduce? • Growth • Repair • Two identical copies of DNA split to form two identical cells • Both daughter cells are completely identical • They have the same DNA • Several Phases • Prophase • Metaphase • Anaphase • Telophase • PMAT

  10. Prophase • Nuclear membrane disintegrates • Nucleolus disappears • Chromatin condenses to form chromosomes • Mitotic spindle forms between poles

  11. Metaphase • Chromosomes attach to mitotic spindle and align along the equator of the cell

  12. Anaphase • Microtubules shorten moving chromosomes to opposite poles

  13. Telophase • Chromosomes reach the poles • Nuclear envelope reforms • Nucleolus reappears • Chromosomes become chromatin

  14. CytokinesisCytokinesis- division of the cytoplasm Animal Cells • No cell wall • Microtubules constrict and pinch off Plant Cells • Has a cells wall • A cell plate forms between the two daughter nuclei • Cell walls form on the sides of the plate

  15. Cell Check Points • Check points – quality control mechanisms • End of G1- DNA Damage check • Many others • If there is a problem the cell cycle stops and the cell goes through apoptosis

  16. Apoptosis • Programmed cell death • Occurs in many embryonic cells • You don’t have a tail, or webbed fingers and toes… you once did • Occurs in cells that are damaged beyond repair or can become cancerous

  17. Cancer • Cancer is uncontrolled growth and division of cells • Cancer cells can kill an organism by crowding out normal cells resulting in the loss of tissue function • Cancer cells outcompete other cells for nutrients

  18. Causes of Cancer • Cancer is caused by mutations • Environmental Factors • Carcinogens- substances know to cause cancer • Age • Older people’s cells have divided for a longer period of time • more chances of mutation • Genetics • Inheriting a mutated gene from a parent • p53 gene

  19. Stem Cells • Unspecialized cells that can develop into specialized cells under the right conditions

  20. Stop

  21. MeiosisWhy can’t a sexual organism produce offspring through mitosis?

  22. Meiosis • Chromosome and Chromosome Number • Human body cells have 46 chromosomes • Skin • Muscle • Each Parent contributes 23 chromosomes • Homologous chromosomes 1 of 2 paired chromosomes, one from each parent

  23. Meiosis • Chromosome and Chromosome Number • Same length • Same centromere position • Carry genes that control the same inherited traits • To count chromosomes count centromeres

  24. Meiosis • The sexual life cycle in animals involves meiosis • Produces gametes • When gametes combine in fertilization, the number of chromosomes is restored

  25. Meiosis - Stages • Reduces chromosome number by ½ through separation of homologues • Two cell divisions • Meiosis I • Meiosis 2

  26. Meiosis • Consist of 2 Divisions • Produces 4 haploid cells that are not identical • Results in genetic variation

  27. Crossing Over • Takes Place in Prophase of Meiosis I • Crossing over produces exchange of genetic information • Crossing over- chromosomal segments are exchanged between a pair of homologous chromosomes

  28. Mitosis vs. Meiosis

  29. Sexual Types of Reproduction Asexual Beneficial genes multiply faster of time Genetically diverse from its parents The organism inherits all of its chromosomes from a single parent The new individual is genetically identical to its parent

  30. Types of Stem Cell Embryonic Stem Cells Adult Stem Cells Found in various tissues in the body May be used to maintain and repair the same kind of tissue Less controversial because the adult stem cells can be obtained with the consent of their donor • After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells. • These cells have not become specialized • They can become any cell in the body

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