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Cellular Reproduction

Cellular Reproduction. All of Chapter 8. Recall that…. nucleotide – a monomer of DNA or RNA consists of nitrogen base, a sugar, and a phosphate group DNA or deoxyribonucleic acid – a double helix nucleic acid – hereditary information

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Cellular Reproduction

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  1. Cellular Reproduction All of Chapter 8

  2. Recall that… • nucleotide – a monomer of DNA or RNA consists of nitrogen base, a sugar, and a phosphate group • DNA or deoxyribonucleic acid – a double helix nucleic acid – hereditary information • RNA or ribonucleic acid – nucleic acid consisting of single strand with ribose and uracil unlike DNA • Nucleic acid – organic molecule that stores & carries important info for cell function

  3. Cell Division: • All cells are derived from preexisting cells (Cell Theory) • Cell division - process where cells produce new cells

  4. Cell division differs in prokaryotes (bacteria) & eukaryotes (protists, fungi, plants, & animals) • Some tissues must be repaired often i.e. lining of gut, white blood cells, skin cells w/a short lifespan  • Other cells do not divide at all after birth i.e. muscle & nerve 

  5. Reasons for Cell Division: • Cell growth • Repair & replacement of damaged cell parts • Reproduction of/ species

  6. Copying DNA:  • each new cell must get a complete set of the DNA molecules b/c instructions are in DNA • DNA must be copied (replicated, duplicated) before cell division

  7. Chromosomes & Their Structure: • The plans for making cells are coded in DNA • DNA, deoxyribose nucleic acid, a long thin molecule that stores genetic info • DNA in human cell consists of ~ six billion pairs of nucleotides • DNA is organized into giant molecules called chromosomes

  8. Chromosomes are made of protein & a long, single, tightly-coiled DNA molecule visible only when the cell divides http://highered.mcgraw-hill.com/olc/dl/120073/bio14.swf mitosis

  9. When a cell is not dividing DNA is less visible & is called chromatin • DNA in eukaryotic cells wraps tightly around proteins called histones to help pack the DNA during cell division • Nonhistone proteins help control the activity of specific DNA genes

  10. Kinetochore proteins bind to centromere and attach chromosome to the spindle in mitosis • Centromeres hold duplicated chromosomes together before they separate in mitosis • Telomeres are the ends of chromosomes which are important in cell aging • When DNA makes copies of itself before cell division, each half of the chromosome is called a sister chromatid

  11. DNA of prokaryotes (bacteria) is one, circular chromosome attached to/ inside of/cell membrane

  12. Chromosome Numbers: • Human body cells have 23 pairs of chromosomes or 46 chromosomes (diploid or 2n number- cells that have 2 sets of chromosomes) • The 2 chromatids of a chromosome pair are called homologues (have genes for the same trait at the same location)

  13. Homolog

  14. Human body cells are somatic cells undergo mitosis. Human reproductive cells or gametes (sperms & eggs) have one set or 23 chromosomes (haploid or n number)

  15. Fertilization, joining o/egg & sperm, restores diploid chromosome number in/zygote (fertilized egg cell) • Sex chromosomes, either X or Y, determine the sex o/organism XX = female XY = male

  16. autosomes – all other chromosomes, except X & Y • Karyotype – a photomicrograph of chromosomes from a dividing cell arranged in pairs by size, long to short, ending w/sex chromosomes • A human karyotype has 22 pairs of autosomes and 1 pair of sex chromosomes (23 total)

  17. What sex is this organism?

  18. Genes: • gene - section of DNA which codes for a protein • Each gene codes for ONE protein • Humans have ~ 50,000 genes or 2000/ chromosome • About 95% o/DNA in chromosome is "junk" that does not code for any proteins

  19. References • http://sps.k12.ar.us/massengale/cell_division_notes.htm

  20. Cell Division 8.2

  21. Cell Cycle: • Cells go thru phases or a cell cycle during their life before they divide to form new cells  • The cell cycle includes 2 main parts --- interphase, and cell division

  22. Cell division includes • mitosis (nuclear division) • cytokinesis (division of the cytoplasm) • Interphase – "resting stage" longest part of a cell's life cycle • cell isn't dividing • Cells grow, develop, & carry on all their normal metabolic functions • 3 parts --- G1, S, & G2 phases

  23. Interphase: • G1 or 1st Growth Phase occurs after a cell division • Cells mature & inc in size by making more cytoplasm & organelles while carrying normal metabolic activities • S or Synthesis Phase follows  G1  and the genetic material of the cell (DNA) is copied or replicated 

  24. Interphase cont’: • S or Synthesis Phase follows  G1  • genetic material of the cell (DNA) is copied or replicated 

  25. G2 or 2nd Growth Phase - occurs after S Phase - cell makes all structures needed to divide

  26. Cell division in Prokaryotes: • Prokaryotes i.e.bacteria don’t have a nucleus • Binary fission – process of dividing into 2 identical new cells • asexual method of reproduction

  27. Binary fission cont’ • chromosome (attached to cell membrane) makes a copy of itself and cell grows to 2X normal size • Next, a cell wall forms btw/chromosomes & parent cell splits into 2 new identical daughter cells (clones)

  28. Cell Division in Eukaryotes: • Eukaryotes have a nucleus & membrane-bound organelles which must be copied exactly so the 2 new cells formed from division will be exactly alike • original parent cell & 2 new daughter cells must have identical chromosomes • DNA is copied in the S phase o/cell cycle & organelles, found in the cytoplasm,  are copied in the Growth phases • Both the nucleus (mitosis) and the cytoplasm (cytokinesis) must be divided during cell division in eukaryotes

  29. Stages of Mitosis: • Mitosis - Division o/nucleus occurs 1st • asexual method of reproduction • 4 stages • Prophase • Metaphase • Anaphase • Telophase

  30. Prophase: • Chromosomes become visible when they condense into sister chromatids • Sister chromatids attach to each other by the centromere • Centrioles in animal cells move to opposite ends of cell • Spindle forms from centriole (animals) or microtubules (plants) • Kinetochore fibers of spindle attach to centromere • Polar fibers of spindle extend across cell from pole to pole • Nuclear membrane dissolves • Nucleolus disintegrates

  31. Metaphase: • Chromosomes line up in center or equator of the cell attached to kinetochore fibers of the spindle

  32. Anaphase: • Kinetochore fibers attached to the centromere pull the sister chromatids apart • Chromosomes move toward opposite ends of cell

  33. Telophase: • Nuclear membrane forms at ea end o/cell around the chromosomes • Nucleolus reforms • Chromosomes become less tightly coiled & appear as chromatin again • Cytokinesis begins

  34. Cytokinesis: • Cytoplasm of the cell and its organelles separate into 2 new daughter cells • In animals, a groove called the cleavage furrow forms pinching the parent cell in two

  35. Cytokinesis cont’ • In plants, cell plate forms down the middle o/cell where the new cell wall will be

  36. Summary of Mitosis: • Interphase Cell matures & carries on normal activities DNA copied & appears as chromatin Nucleolus visible

  37. Early Prophase • Chromosomes condense & become visible • Centrioles separate & spindle starts forming

  38. Late Prophase • Spindle forms with aster at each pole • Nuclear membrane & nucleolus disintegrate • Centromere of chromosomes attaches to spindle fibers

  39. Metaphase • Chromosomes line up at the equator of the cell attached to kinetochore fibers of spindle

  40. Anaphase • Centromeres split apart • Homologs move to opposite poles of the cell

  41. Telophase/Cytokinesis • Nuclear membrane & nucleolus reform • Cell pinches into 2 cells in animals • In plants, a cell plate separates the 2 new cells

  42. Cancer is Uncontrolled Mitosis: • Mitosis must be controlled, otherwise growth will occur w/out limit (cancer) • Control is by special proteins produced by oncogenes • Mutations in control of proteins can cause cancer

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