Cell Growth, Division and
Reproduction
B1
B1. Basic Biological Principles
1. Describe the events that occur during 3 stages of the
cell cycle: interphase, nuclear division, cytokinesis.
2. Compare and contrast processes and outcomes of
mitosis and meiosis.
3. Explain how genetic information is inherited.
4. Explain the functional relationships between DNA,
genes, alleles and chromosomes and their roles in
inheritance.
B1. Vocabulary
Allele
genetics
Allele frequency inheritance
Cell cycle
meiosis
Chromosomes
mitosis
Crossing over
nondisjunction
Cytokinesis
nucleus
Deoxyribonucleic acid (DNA)
DNA replication
Gene
gamete
Cell Size
1. Information Overload
– Large cells place more demands on the DNA to provide
what the cell needs to live
ANALOGY: What would
happen to a growing town
if it continued to grow?
Cell Size
2. Exchanging Materials
– Cells rely on movement of material across the cell
membrane
– Large cells have trouble moving enough nutrients in and
wastes out
ANALOGY: Traffic Problems
Cell Size
ANALOGY: Lots of
Growth can mean
lots of trouble both
in a town and in a
cell
Cell Size
A process by which a cell divides into two new cells
• Solves the problem of overloading DNA and not
being able to get enough materials in or out
Model it…
• How does the surface area of a cube change as its
volume increases?
• How does the relationship support the
information learned today.
The Process of Cell Division
• Cells store information in DNA
• DNA is packaged into chromosomes
– Prokaryotes = single circular chromosome
– Eukaryotes = many chromosomes
•
Chromatin = all of the chromosomes in the nucleus
The Process of Cell Division
• DNA is copied before cell
division (replication)
• When a cell is not dividing,
DNA is uncoiled (chromatin)
• During division, DNA coils up
(condenses) and individual
chromosomes can be seen
Which is easier to separate?
Chromosomes during cell division
Chromosomes before cell division
The Process of Cell Division
• Once replicated, each
chromosome consists of
two identical sister
chromatids held
together at the
centromere
The Process of Cell Division
 The series of events a cell goes through as it grows
and divides
– growth
– DNA replication
– Cell division
 End Result = two new daughter cells genetically
identical to the parent cell
The Process of Cell Division
•
•
•
•
•
happens quickly
begins when the cell reaches a certain size
is a form of asexual reproduction
results in a new organism being formed
called binary fission
The Process of Cell Division
Multiple stages with checkpoints
1. Interphase
a) G1: Cell Growth
b) S: DNA Replication
c) G2: Preparation for division
2. Cell division (also called M phase)
a) Mitosis: division of the nucleus
i.
ii.
iii.
iv.
Prophase
Metaphase
Anaphase
Telophase
b) Cytokinesis: division of the cytoplasm
The Process of Cell Division
The Process of Cell Division
 PROPHASE
–
–
–
–
–
First phase of mitosis
Chromosomes are visible
Nucleus disintegrates
Spindle fibers form
Centrioles migrate
The Process of Cell Division
 METAPHASE
– Second phase of mitosis
– Chromosomes line up across
the center of the cell
The Process of Cell Division
 ANAPHASE
– Third phase of mitosis
– Sister chromatids separate
and move to opposite sides
of the cell
The Process of Cell Division
 TELOPHASE
– Final phase of mitosis
– Chromosomes unwind
– Nucleus reforms around
each new set of
chromosomes
– Spindles break down
Take a Break…QUICK CHECK
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Cell Division and Reproduction
•
•
•
•
Cell division that results in a new organism
Reproduction by a single parent
Offspring are clones of parent
Advantages: Quick - organisms well suited for an
environment can reproduce very quickly
• Disadvantages: Lack of genetic diversity
Cell Division and Reproduction
•
•
•
•
Results from the joining of two different cells
Offspring have a mix of DNA from both parents
Advantages: Offspring are genetically different
Disadvantages: Slow – takes time to mature and
find a mate
Think about this…
• How many chromosomes do you have in your
cells?
• How many of those chromosomes came from
dad?
• How many of those chromosomes came from
mom?
Cell Division and Reproduction
• Homologous chromosomes = chromosomes that
carry the same types of genes
– An organism with two parents must receive a set of
genes from both parent
• Reproductive cells therefore can only carry a half of
the chromosomes
• When an organism produces reproductive cells
(sperm and egg), homologous chromosomes must
separate
– Meiosis is the process that ensures the separation of
homologous chromosomes
Cell Division and Reproduction
Cell Division and Reproduction
• Cell division that produces reproductive cells
• Begins with interphase (DNA replicated)
• Two rounds of division
– Meiosis I – homologous chromosomes
– Meiosis II – sister chromatids
– Each round of division consists of prophase,
metaphase, anaphase and telophase
Cell Division and Reproduction
• End result of meiosis is different from mitosis
– 4 cells produced
– Each cell contains half the # of chromosomes that are
needed in the organism (haploid)
– Cells that form are genetically different
Cell Division and Reproduction
• Begins with interphase (DNA replicated)
• Two rounds of division
– Meiosis I – homologous chromosomes
– Meiosis II – sister chromatids
– Each round of division consists of prophase,
metaphase, anaphase and telophase
Cell Division and Reproduction
 Prophase I
• Homologous chromosomes pair up
• Crossing over occurs between homologous
chromosomes (exchange of genetic info)
– Produces new combinations of genes
Keystone Prep Questions
1. Which statement best describes the
phase of the cell cycle shown?
A. The cell is in prophase of mitosis because the number of
chromosomes has doubled.
B. The cell is in prophase I of meiosis because the number of
chromosomes has doubles.
C. The cell is in telophase of mitosis because the cell is
separating and contains two copies of each chromosome.
D. The cell is in telophase of meiosis because the cell is
separating and contains two copies of each chromosomes
Keystone Prep Questions
2. Mitosis and Meiosis are processes by which animal
and plant cells divide. Which statement best
describes a difference between mitosis and meiosis?
A.
B.
C.
D.
Meiosis is a multi-step process.
Mitosis occurs only in eukaryotic cells.
Meiosis is used in the repair of an organism.
Mitosis produces genetically identical daughter cells.