Download Cell Reproduction

PowerPoint® Lecture Slide Presentation by Robert J. Sullivan, Marist College
Human Biology
Concepts and Current Issues
Second Edition
MICHAEL D. JOHNSON
CHAPTER 17
CELL REPRODUCTION &
DIFFERENTIATION
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Cell Cycle
Figure 17.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Cell Cycle: Creates New Cells
• Interphase: between cell divisions
• G1: primary growth phase
• S: synthesis of DNA for next cell division
• G2: final growth phase
• Mitotic phase: cell division
• Mitosis: DNA distributes, nucleus divides
• Cytokinesis: cell divides
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
DNA Replication
• Process:
• DNA strands uncoil and “unzip”
• DNA nucleotides are positioned and linked by
DNA polymerase
• Old and new sides are “zipped” together
• Centromere holds duplicate strands together
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
DNA Mutations and Mechanisms of
Repair
• Mutations: most frequent during DNA replication
• Causes: chemical and physical forces
• Effects: none (neutral), nudge in evolution
(beneficial), cell death or cancer (harmful)
• Mechanisms of Repair: DNA repair enzyme
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Transcription of a Gene into mRNA
Figure 17.6
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Protein Synthesis: Transcription
•Process:
• DNA for a gene unwinds
• RNA polymerase assists in copying base sequence
in RNA nucleotides
• Primary transcript made, includes introns and
exons
• Introns edited out
• Messenger RNA strand produced
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Genetic Code of mRNA
Figure 17.7
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Genetic Code
• Codon: sequence of three RNA bases, code for
amino acids
• Duplicate codons: all but one amino acid
(methionine) have more than one codon
• DNA grammar
• Start: AUG (methionine), begin all genes
• Stop: UAA, UAG, UGA, one ends each gene
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Three Steps of Translation
Figure 17.8
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Protein Synthesis: Translation
• Components: messenger RNA, transfer RNA,
ribosomes of ribosomal RNA and proteins
• Process:
• Initiation: initiator tRNA finds start codon, binds
ribosome and mRNA
• Elongation: tRNA brings specific amino acids to
developing protein chain
• Termination: stop codon terminates developing
chain, protein is released from ribosome
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Cell Reproduction: Mitosis and
Cytokinesis
• Mitosis
• Phases:
• Prophase: mitotic spindle formed, centrioles migrate to cell
poles, chromosomes condense, nuclear membrane dissolves,
metabolic activity decreases
• Metaphase: duplicate choromosomes form single line at the
equator between cetriole poles
• Anaphase: duplicate choromosomes separate, are pulled
toward poles by microtubules, centromeres broken
• Telophase: reverse of prophase, duplication of centrioles
• Cytokinesis: cell separates into two identical cells
(diploid)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Cell Reproduction: Meiosis
• Process: two cell divisions, reducing chromosome
number by half
• Meiosis I
• Metaphase: pairs of chromosomes line up, double
line
• Crossing over between homologous pairs possible
• Anaphase: pairs of chromosomes separated
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Cell Reproduction: Meiosis
(cont.)
• Meiosis II
• Same process as mitosis
• Anaphase: duplicated chromosomes (chromatids)
separate
• Telophase: nuclei made with half the chromosome
number (haploid)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Sex Differences in Meiosis
• Males: four sperm produced from each meiotic
division, all viable
• Female: one egg and one polar body produced
from each meiotic division, only the egg viable
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Regulation of Cell Reproduction
• Selective gene expression: only those genes
needed are expressed
• Repressor proteins: prevent gene expression
• Activator proteins: needed to activate genes
• Regulatory genes: code for repressor and activator
proteins
• Structural genes: code for an enzyme or structural
protein
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Regulation of Cell Reproduction
(cont.)
• Environmental factors: can modify cell cycle at
three natural stopping points
• G1: if cells do not divide in adults, cycle stops
• Before mitosis
• Arrest mitosis at metaphase
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
Environmental Factors Influencing
Cell Differentiation
• Differentiation in early development
• After 8-cell stage, cells exposed to different
environments inside versus outside the ball
• Cloning: can occur at 8-cell stage
• Differentiation in later development
• Two factors:
• Developmental history of earlier cells
• Local environment
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.