Cell cycle and
Reproduction
BIO…
LIFE….
THINK ABOUT THIS:
What do we do in our lifetime?
What are the major stages of our life?
What are the Major stages of
physical development in our lives?
 What would it look like
if we put this into a pie
chart?
Imagine you are a bacteria:
What are the major stages in your
life?
TRY ME:
 What is A? B? C?
 What is D/E/F/G collectively
called?
 What is D?
 What is E?
 What is F?
 What is G?
The life of a cell
 Cells have a life cycle just like we do- born, grow, reproduce,
and die.
 They only spend part of
their life cycle reproducing (M)- mitosis
Cell Cycle
1. Interphase (G1, S, G2) – cell grows,
prepares to divide (G phases) and DNA
replicates (S phase)
2. Mitosis: nucleus divides; each nuclei
winds up with the same # and kind of
chromosomes as the parent (P-M-A-T)
3. Cytokinesis: division of cytoplasm
COMING UP IN THIS CLASS…
 In the upcoming months, we will be analyzing what happens stages
in great detail. Which stage do you think the following upcoming
material will focus on?
Topics to cover:
- DNA structure and replication?
- DNA structure and making
Proteins (growth and homeostasis)?
- Cell reproduction (asexual- bacteria)?
- Cell reproduction (growth- multicellular)?
 Cell cycle: repeating sequence of cellular
growth and division during the life of an
organism; check points trigger the next
stage of the cycle
https://www.youtube.com/watch?v=65SO
DTL_QsA
WHY?
THINK: Why do we have cycles and cells split? Why doesn’t
the cell just get bigger and bigger?
 LIMITS TO CELL GROWTH AND LIFE CYCLE- PART 1
- NOTES- Handout AND PPT
So what happens when cells get
TOO LARGE????
 THEY SPLIT- MITOSIS.
 BUT BEFORE WE TALK ABOUT WHAT CELLS DO
EXACTLY IN MITOSIS, LET’S THINK ABOUT WHY CELLS
DON’T JUST SPLIT ALL THE TIME????
Or in other words….
What happens if things go
wrong with checkpoints?
THINK ABOUT THIS!!!!
 Loss of Control of the Cell Cycle
 If checkpoints are not working properly,
the cell cycle can cause the cell to grow
uncontrollably
 leads
to cancer .
THINKING QUESTION:
What biomolecule controls checkpoints?
AMEOBA SISTERS:
https://www.youtube.com/watch?v=lpAa4TWjHQ4&list=PLwL0Myd7Dk1F1ppDaLx3ygO_7xA-yyd4&index=2
PROTEINS AND CELL CYCLE
REGULATION: 10.3
 CYCLINS, GROWTH FACTORS, APOPTOSIS AN D
CANCER.- Section 10.3-
And what controls the making of proteins? DNA
SO WHAT’S THE DIFFERENCE BETWEEN
PROKARYOTIC AND EUKARYOTIC DNA
How Is the DNA in Eukaryotic
Chromosomes Organized?

Eukaryotic chromosomes differ from prokaryotic chromosomes
in important
ways
 Eukaryotic chromosomes are separated from the
cytoplasm by a membrane-bound nucleus
 Eukaryotic cells always have multiple chromosomes
 Eukaryotic chromosomes are longer and have more
DNA than prokaryotic chromosomes (human
chromosomes are 10 to 80 times longer and have 10
to 50 times more DNA)
 These differences account for the complexity of
eukaryotic cell division
How Is the DNA in Eukaryotic
Chromosomes Organized?
 The eukaryotic chromosome consists of a linear DNA
double helix bound to proteins





Each human chromosome contains a single DNA double helix, about 50 million to 250
million nucleotides long
Most of the time, the DNA in each chromosome is wound around proteins called histones
These DNA-histone spools are further folded into coils
Another layer of folding occurs as the coiled strand folds into loops, which are then
attached to protein scaffolding, so that the chromosome is 1,000 times shorter than the
extended DNA molecule
During cell division, more proteins fold up the DNA and histones, until it is 10 times
shorter than during its resting state
Figure 9-4 Chromosome structure
DNA double helix
histone proteins
DNA wound
around histone
proteins
Coiled DNA/histone beads
Loops attached
to a protein scaffold;
this stage of partial
condensation typically
occurs in a nondividing
cell
protein scaffold
Folded
chromosome,
fully condensed
in a dividing cell
DIFFERENCES Cont…
WHAT DO THE AMEOBA SISTERS HAVE TO SAY
ABOUT THIS???
https://www.youtube.com/watch?v=ruBAHiij4EA
HOW ARE THESE TERMS RELATED?
FIRST…Find out what they mean.
WE WILL REVIEW…
THEN…Make a concept map.
 DNA HISTONES GENES SISTER CHROMATIDS CENTROMERE
 CHROMOSOMES LOCI TELOMERE-
GENES, CHROMOSOMES, and DNA
The DNA in a chromosome consists of two long strands
of nucleotides wound around each other, as a ladder
would look if it was twisted into a corkscrew shape
 This structure is called a double helix
 The units of inheritance, called genes, are segments
of DNA
 The specific sequence of nucleotides in genes spells
out the instructions for making the proteins of a cell
 When a cell divides, it replicates its DNA to make two
identical copies, and gives each daughter cell one of
the two copies
9.3 How Is the DNA in Eukaryotic
Chromosomes Organized?
 Genes are segments of the DNA of a chromosome
 Genes are sequences of DNA from hundreds to
thousands of nucleotides long
 Each gene occupies a specific place, or locus
(plural, loci) on the chromosome
9.3 How Is the DNA in Eukaryotic
Chromosomes Organized?
 In addition to genes, every chromosome has
specialized regions that are crucial to its structure and
function
 Two telomeres
 One centromere
 The two ends of a chromosome consist of repeated nucleotide sequences called
telomeres, which are essential for chromosome stability
9.3 How Is the DNA in Eukaryotic
Chromosomes Organized?
 Genes are segments of the DNA of a chromosome (continued)
 The second specialized region of the chromosome is
the centromere, which has two principal functions
1. It temporarily holds two daughter DNA double helices together after DNA
replication
2. It is the attachment site for microtubules that move the chromosomes during cell
division
Eukaryotes
 Chromosomes carry the DNA…but you need
two IDENTICAL COPIES of DNA to go to the 2
cells
 chromosome #
varies between
species
 humans46
chromosomes
(23 pairs)
REMEMBER: The life of a cell
 Before cells
can divide,
DNA needs to be replicated
So the code can be
passed on.
Which phase does this happen in????
 DNA Replication
 Process of copying a double stranded
DNA to form 2 double stranded
molecules
 Basis of biological inheritance used by
all living things
 Occurs before a cell divides (mitosis)

DNA Replication
1. Enzymes break the hydrogen bonds between the
bases so the chains of DNA can separate or
unwind

DNA Replication
2. Other enzymes add
new nucleotides,
which form new
hydrogen bonds
with their
complimentary
nucleotide.
Red = original strand
Blue = new strand

DNA Replication
 Results in 2 semi-conservative double
stranded molecules
WHAT IS THE ROLE OF:
HelicaseSSBReplication fork-
DNA Polymerase-
ANIMATIONS OF DNA REPLICATION
http://www.bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.s
wf
http://www.mcb.harvard.edu/Losick/images/TromboneFINALd.swf
http://highered.mcgrawhill.com/sites/0072556781/student_view0/chapter11/animation_quiz_2.html
http://www.sinauer.com/cooper/4e/animations0601.html
AMEOBA SISTERS:
https://www.youtube.com/watch?v=5qSrmeiWsuc&index=1&list=PLwL0Myd7Dk1F1p
p-DaLx3ygO_7xA-yyd4
NOW ONCE THE DNA IS REPLICATED, THE CELL
CAN DIVIDE!
Asexual Reproduction
(Mitosis)

Asexual Reproduction
 Purpose of cell division:
 in simpler organisms: reproduction of
offspring
 in complex organisms: increase number
and size of cells; repair damaged cells
 only 1 parent is required
 parent DNA is passed onto offspring,
therefore, offspring are IDENTICAL to parent
MITOSIS: PHASES
WHAT ARE THE PHASES
OF MITOSIS
WHAT HAPPENS IN EACH
PHASE???
DNA replicates in
interphase?
Which part of cell
cycle???
What happens in
each:
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html#
no cell wall
cell wall
Mitosis
parent
cell
46
chromosomes
92
chromosomes
46
chromosom
es
daughter
cells
46
chromosom
es
AMEOBA SISTERS:
https://www.youtube.com/watch?v=gwcwSZIf
KlM&list=PLwL0Myd7Dk1F1ppDaLx3ygO_7xA-yyd4&index=3
Figure 9-8 The eukaryotic cell cycle
G1: cell growth and
differentiation
G2: cell
growth
and
preparation
for cell
division
S: synthesis
of DNA;
duplication of
chromosomes
CATEGORIES OF CELLS?
 Most multicellular organisms have three categories of
cells
1.Stem cells
2.Other cells capable of dividing
3.Permanently differentiated cells
STEM CELLS
 SO WHAT’S SO SPECIAL ABOUT STEM CELLS
ANYWAYS???
 Stem cells have two important characteristics: selfrenewal, and the ability to differentiate into a variety of
cell types
 Stem cells self-renew because they retain the ability to divide, perhaps for the entire
life of the organism
 Stem cells include most of the daughter cells formed by the first few cell divisions of
a fertilized egg, as well as a few adult cells
STEM CELLS….
 When a stem cell divides, usually one daughter remains a stem cell, thus
continuing the line; the other daughter eventually differentiates
 Some stem cells in early embryos can produce any of the specialized cell types of
the entire body
TYPES OF CELLS
 Other cells capable of dividing
 Many cells of the bodies of embryos, juveniles, and adults can divide
 Each type of cell typically differentiates into only one or two types of cells
 Dividing liver cells, for example, can only become
more liver cells
 Permanently differentiated cells differentiate and
never divide again
Why Do Cells Divide?
 Cell division is required for growth and asexual reproduction
 Reproduction in which offspring are formed from a
single parent, without having a sperm fertilize an egg,
is called asexual reproduction
 Clones are offspring genetically identical to the
parent and to each other, produced through asexual
reproduction
ASEXUAL REPRODUCTION
 Bacteria and single-celled eukaryotic organisms
reproduce asexually
 Some multicellular organisms, like Hydra, reproduce
asexually
 Many plant and fungi reproduce both asexually and
sexually
 Groves of aspen may be produced asexually by shoots growing up from the root system
of a single parent tree
 Aspen may also reproduce sexually from seeds
Figure 9-2 Cell division enables asexual reproduction
The trees in this grove
have already lost their
leaves
Dividing bacteria
The trees in this grove
have begun to change
color
Cell division in Paramecium
The trees in this grove
are still green
bud
Hydra reproduces asexually by budding
A grove of aspens often consists of genetically
identical trees produced by asexual reproduction
 Asexual Reproduction
ALL substances must pass through a cell membrane
to enter and exit a cell
 smaller cells  higher surface-area-to-volume
ratio  can exchange materials faster
 cell division occurs when a cell reaches a certain
size
 Types of Asexual Reproduction
Prokaryotes
(bacteria):
 binary fission:
1 bacteria cell
divides into
2 bacteria cells
of the same size

Types of Asexual Reproduction
Eukaryotes
 budding: part of
the parent organism
pinches off and
forms a new
organism.
Yeast
(fungus
Hydra
(protist
)