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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


Cell Cycle

• Defines changes from formation of the cell until it reproduces

• Includes:

• Interphase

• Cell division (mitotic phase)

Copyright © 2010 Pearson Education, Inc. Figure 3.31

G1

Growth

SGrowth and DNA

synthesis G2

Growth and finalpreparations for

divisionM

G2 checkpoint

G1 checkpoint(restriction point)


Nuclearpores

mRNA

Pre-mRNARNA Processing

Transcription

Translation

DNA

Nuclearenvelope

Ribosome

Polypeptide


Transcription

• Transfers DNA gene base sequence to a complementary base sequence of an mRNA


Translation

• Converts base sequence of nucleic acids into the amino acid sequence of proteins

• Involves mRNAs, tRNAs, and rRNAs


Genetic Code

• Each three-base sequence on DNA is represented by a codon

• Codon—complementary three-base sequence on mRNA


SECOND BASE

UUG

UUA

UUC

UUUPhe

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

UAUTyr

CAG

CAA

CAC

CAUHis

Gln

AAG

AAA

AAC

AAUAsn

Lys

GAG

GAA

GAC

GAUAsp

Glu

UGC

UGUCys

Trp

CGG

CGA

CGC

CGU

Arg

AGG

AGA

AGC

AGUSer

Arg

GGG

GGA

GGC

GGU

Gly

UAA Stop UGA Stop

AUGMet orStart

UAG Stop UGG

U C A G

G

A

C

U

G

A

C

U

G

A

C

U

G

A

C

U

U

C

A

G


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.


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


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.

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