Standard 6
Emily and Cammie
Describe the roles of
mitotic and meiotic
divisions during
reproduction, growth,
and repair of cells.
What is Mitosis?
• Mitosis occurs when a eukaryotic cell reproduces.
This takes place in plant & animal cells.
• Mitosis produces cells that are exactly like the
previous ones.
• This is the way that worn out cells replace
themselves in our liver, lungs, blood etc.
Chromosome Numbers
• If there are 46 chromosomes in the
Mother cell (original) then there will also
be 46 chromosomes in each of the
daughter cells (the two cells that result)
46 is the diploid number of chromosomes
The diploid number of chromosomes is
shown as 2N
Stages of Mitosis
•
•
•
•
•
•
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Prophase
• The
chromosomes
double during
this phase.
Metaphase
• The
chromosomes
line up in the
middle and
attach to the
spindle fibers.
Meta means middle
Anaphase
• The spindle
fibers pull the
daughter
chromosomes
to opposite
sides of the
cell.
They move AWAY from the middle in ANAPHASE
Telophase and Cytokinesis
• The cell cleaves
& divides into two
cells.
Interphase
• The cell
grows.
• When it gets
to a certain
size it begins
the process
of Mitosis
Mitosis and Cell Repair
Certain body cells are
needed to be regenerated
occasionally because of
damage. When cells
repair, for example your
skin, they undergo mitosis
to create more skin cells
to heal the wound.
Mitosis and Growth
Every time a single cell
duplicates in mitosis it
causes the organism to
grow because it has
more cells. Once that cell
duplicates, it and it’s
duplicate continue to
make more identical
cells, increasing the cell
count.
• Mitosis produces cells
that are IDENTICAL.
• For this reason, it does
NOT increase variation
• Mitosis produces
• diploid cells.
What is Meiosis?
Meiosis the way that sex cells (like eggs &
sperm) divide. You begin with 46 chromosomes in
the original cell and end up with 4 cells, each with 23
chromosomes. 23 is one half of 46, so we call it our
HAPLOID number.
Meiosis is the way that “ME”
was made.
The egg & sperm both divide by
Meiosis
Me - Meiosis
Phases of Meiosis
46
Meiosis I
Meiosis II
46
23
23
46
23
All sex cells (gametes) reproduce by Meiosis.
Examples: Plant pollen & eggs, animal eggs & sperm
23
Meiosis and Variation
Crossing over is when chromosomes
exchange pieces of themselves with each
other. This produces a unique gene
combination and variation within the
species.
Meiosis leads to genetic variation
So you are a “one of a kind” combination of
your parent’s genes.
Meiosis and Reproduction
Meiosis produces a sex cell
(gamete) with ½ the number
of chromosomes of a
normal body cells.
During sexual reproduction,
the egg & sperm come
together to form a new &
unique offspring with a
combination of genes.
This diversity helps build
strong offspring
QUESTION
TIME!
Question 1
Meiosis and mitosis are two
different reproductive
processes. What happens
ONLY during meiosis?
A. Crossing over occurs
B. Replication of organelles
C. Disappearance of the nucleolus
D. Complete breakdown of the nuclear membrane
Answer 1
Crossing
over occurs
Crossing over leads to genetic variation.
Question 2
Which statement is correct?
A. Meiosis is a way to reproduce, but mitosis is not.
B. Meiosis is a way to create diversity, but mitosis is not.
C. During mitosis, chromosomes are copied, but during
meiosis chromosomes double.
D. During mitosis, chromosomes numbers double, but
during meiosis chromosome numbers remain
constant.
Answer 2
Meiosis is a way to create diversity, but mitosis
is not.
In meiosis half the genetic content is from the mom
and half is from the dad so the offspring it
produces has unique characteristics. In mitosis
the cell just splits so there is no diversity.
Question 3
Which process requires meiosis?
A. Egg production
B. Bacterial fission
C. Flatworm regeneration
D. Vegetative propagation
Answer 3
Egg production
Because egg production is done sexually
Question 4
Which statements about cell division are CORRECT?
1. Mitosis leads to variation in species.
2. Meiosis leads to variation in a species.
3. Mitosis produces haploid cells used in reproduction.
4. Meiosis produces haploid cells used in reproduction
A. Statements 1 and 3
B. Statements 1 and 4
C. Statements 2 and 3
D. Statements 2 and 4
Answer 4
Statements 2 and 4
Meiosis leads to variation in a species and meiosis
produces haploid cells used in reproduction.
Because haploid cells are used in meiosis not mitosis
Question 5
Red blood cells carry oxygen to the body
during respiration and typically have a
lifespan of four months. What is the role of
mitosis in respiration?
A.
B.
C.
D.
Allows cells to absorb oxygen from the air
Causes cells to release oxygen to the body
Helps replace cells that are destroyed or damaged
Produces molecules needed to maintain cell
structures
Answer 5
Helps replace cells that are destroyed
or damaged
It does this to maintain red blood cells.
Question 7
Which reproductive process is
MOST like the regenerative
process of skin cells?
A.
B.
C.
D.
Yeast creating buds
Ovaries forming eggs
Ferns producing spores
Muscles growing in size
Answer 7
Muscles growing in size
The cells grow because the are duplicated.
Question 8
Which cell process is represented by process 1 of reproduction?
Process 2
Process 1
n
2n
n
2n
n
2n
n
A. Meiosis
B. Mitosis
C. Respiration
D. Fertilization
Answer 8
Mitosis
Because it has a 2N or Diploid # of
chromosomes
Question 9
Study the sequence below. Which cellular process
missing from this sequence produces cells having a
chromosome number 2n?
2n
undergo
Skin cells
?
to
form
Having
Skin cells chromosome
number
A. Meiosis
C. Respiration
B. Mitosis
D. Fertilization
2n
Answer 9
Mitosis
Mitosis produces 2N # of
chromosomes.
Question 11
Which is produced by meiosis?
A. 4 Haploid cells
B. 2 Diploid cells
C. 2 Haploid cells
D. 4 Diploid cells
Answer 11
Four haploid cells
In the first stage of meiosis (mitosis) it
makes diploid cells, but in the second
stage, it makes 4 haploid cells.
Question 12
Fill in the blank. Crossing over and
_____ lead to genetic variation.
A. Duplicate Chromosomes
B. Independent assortment
C. Asexual reproduction
D. Fertilization
Answer 12
Independent assortment
Because duplicate chromosomes,
fertilization, and asexual reproduction
cannot lead to variation.
Question 13
Cytokinesis occurs under this
stage of mitosis.
A. Telophase
B. Metaphase
C. Anaphase
D. Interphase
Answer 13
Telophase
Because it is the last phase
Question 14
Fill in the blanks. Cell division is a
process that enables organisms
to _____ and ________.
A. Divide and reproduce
B. Reproduce and distribute
C. Divide and grow
D. Grow and reproduce
Answer 14
Grow and reproduce
Because during mitosis and meiosis, the
cells grow and reproduce.
Question 15
What phase of Mitosis is this cell
in?
A. metaphase
B. anaphase
C. telophase
D. interphase
Answer 15
Telophase
Because there is a cleavage furrow and the
daughter chromosomes arrive at the
poles.