1. PowerPoint ® Lecture Slides prepared by Janice Meeking, Mount Royal College C H A P T E R Copyright © 2010 Pearson Education, Inc. 3 Cells: The Living Units: Part D

2. Copyright © 2010 Pearson Education, Inc. Cell Cycle Defines changes from formation of the cell until it reproduces Includes: Interphase Cell division (mitotic phase)

3. Copyright © 2010 Pearson Education, Inc. Figure 3.31 G 1 Growth S Growth and DNA synthesis G 2 Growth and final preparations for division M G 2 checkpoint G 1 checkpoint (restriction point)

4. Copyright © 2010 Pearson Education, Inc. Figure 3.34 Nuclear pores mRNA Pre-mRNA RNA Processing Transcription Translation DNA Nuclear envelope Ribosome Polypeptide

5. Copyright © 2010 Pearson Education, Inc. Transcription Transfers DNA gene base sequence to a complementary base sequence of an mRNA

6. Copyright © 2010 Pearson Education, Inc. Translation Converts base sequence of nucleic acids into the amino acid sequence of proteins Involves mRNAs, tRNAs, and rRNAs

7. Copyright © 2010 Pearson Education, Inc. Genetic Code Each three-base sequence on DNA is represented by a codon Codon—complementary three-base sequence on mRNA

8. Copyright © 2010 Pearson Education, Inc. Figure 3.36 SECOND BASE UUG UUA UUC UUU Phe Leu CUG CUA CUC CUU Leu AUA AUC AUU Ile GUG GUA GUC GUU Val UCG UCA UCC UCU Ser CCG CCA CCC CCU Pro ACG ACA ACC ACU Thr GCG GCA GCC GCU Ala UAC UAU Tyr CAG CAA CAC CAU His Gln AAG AAA AAC AAU Asn Lys GAG GAA GAC GAU Asp Glu UGC UGU Cys Trp CGG CGA CGC CGU Arg AGG AGA AGC AGU Ser Arg GGG GGA GGC GGU Gly UAAStopUGAStop AUG Met or Start UAGStopUGG UCAG G A C U G A C U G A C U G A C U U C A G

9. Copyright © 2010 Pearson Education, Inc. Mitosis vs. Meiosis Mitosis for the regeneration and replacement of dead and dying cells with 2 new identical daughters which are in essence clones of a parent stem cell. Daughter cells will differentiate into functional cell for the replacement of the dead cell(s) Meiosis different from mitosis in that it serves to produce 4 sex cells (sperm and ova) call gametes with half the number of genes found in other body cells.

10. Copyright © 2010 Pearson Education, Inc. Developmental Aspects of Cells All cells of the body contain the same DNA but are not identical Chemical signals in the embryo channel cells into specific developmental pathways by turning some genes off Development of specific and distinctive features in cells is called cell differentiation Elimination of excess, injured, or aged cells occurs through programmed rapid cell death (apoptosis) followed by phagocytosis

11. Copyright © 2010 Pearson Education, Inc. Theories of Cell Aging Wear and tear theory: Little chemical insults and free radicals have cumulative effects Immune system disorders: Autoimmune responses and progressive weakening of the immune response Genetic theory: Cessation of mitosis and cell aging are programmed into genes. Telomeres (strings of nucleotides on the ends of chromosomes) may determine the number of times a cell can divide.