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CELL DIVISION AND REPRODUCTION
Unit 7
FLASHCARD WARMUP
Chromosome
DNA is coiled to conserve space
and this structure is called a
chromosome. When the DNA
copies to prepare for mitosis, the
two copies are each called
chromatids and are connected
for a while in a doubled
chromosome.
REASONS FOR CELL DIVISION

1. Maintain a workable
volume to surface area ratio;
volume increases faster than
surface area in cells

a larger surface area: volume
ratio is preferable.
2. Growth- multicellular
organisms must increase in
the number of cells to grow
 3. Repair and replacement of
cells lost due to injury or cell
death requires cell division.

Larger
surface area:
volume ratio
Smaller
surface area:
volume ratio
EUKARYOTIC CELL CYCLE

Interphase: Longest part
of the cell cycle; DNA
replication takes place,
carries out life functions
Chromatin: condensed
DNA and proteins, (will
form a chromosome)
 Chromatid: identical
copies of DNA making up a
duplicated chromosome,
attached at centromere
 Doubled chromosome:
nicely packaged and
duplicated DNA
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MITOSIS
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Prophase: Chromosomes
visible, spindles form
Metaphase: chromosomes
move to middle (equator) of
the cell
Anaphase: doubled
chromosomes separate,
chromatids move to opposite
ends of cell
Telophase:spindles
breakdown, nuclear envelope
appears
Cytokinesis: Division of
cytoplasm


Plant Cells: cell plate is
produced and will become cell
wall
Results: Two identical cells
,diploid (2n) –ex. Our cells
have 46 chromosomes
PROBLEMS WITH MITOSIS

Cancer: Uncontrolled cell
division
A cancerous lung tumor
 Benign when it is localized
to one area, malignant when
cancer cells are in blood
stream and move to another
part of the body

TICKET OUT THE DOOR
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Identify the stages
of the cell cycle in
the picture. Write
out the correct
order as given and
match the letter
with the correct
phase.
Interphase
prophase
metaphase
anaphase
telophase
FLASHCARD WARMUP
Mitosis
Meiosis
This type of ASEXUAL
cell division makes
exact copies of a cell. It
is part of a cell’s life
cycle, after normal
growth. The phases of
mitosis are Prophase,
Metaphase, Anaphase,
and Telophase.
(PMAT) One parent
cell divides to become
two daughter cells.
A form of sexual
reproduction. This type of cell
division creates gametes or
sex cells. These are haploid
or have ½ the number of
chromosomes so that the
zygote has the correct
number after fertilization.
TYPES OF REPRODUCTION
Asexual: one source of genetic material,
identical daughter cells
 Advantages: reproduction is fast, less
energy needed, no mate needed,
 Disadvantages: lack of genetic variation
(one thing could wipe out entire population)

TYPES OF ASEXUAL
REPRODUCTION
Binary Fission: cell divides
into 2 equally sized cells
 Budding: produce smaller cells
than parents (ex. hydra and
yeast)
 Sporulation - produces spores

TYPES OF ASEXUAL REPRODUCTION
Vegetative
propagation: a portion
of one plant produces
a new identical plant
 Regeneration: part of
animal is repaired
through cell division

SEXUAL REPRODUCTION
Sexual: two sources of genetic material, makes
four haploid sex cells (gametes)
 Gametes: sperm and egg
 Advantages: genetic variation,
 Disadvantages: requires more time for mating,
risk of unfavorable genetic combinations

Fertilization
TICKET OUT THE DOOR
Give two examples of asexual reproduction and
briefly explain.
 What are the advantages and disadvantages of
asexual reproduction?

FLASHCARD WARMUP
Homologous
Chromosomes
Diploid and
haploid
Each species has a specific
number of chromosomes.
Humans have 46
chromosomes in 23
homologous pairs. Each
homologous pair has one
from the mother and one
from the father.
Homologous chromosomes
have the same traits.
Somatic (body) cells are
diploid, meaning that they
have pairs of chromosomes.
When a cell undergoes
meiosis to prepare for
sexual reproduction, the
chromosome number must
be reduced by half, creating
a haploid cell.
MEIOSIS:
REQUIRES 2 DIVISIONS:
PHASES THE SAME AS MITOSIS

Meiosis I (1st
division):

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Reduces the
chromosome
number;
Result: 2 genetically
different daughter
cells
(1n) 23 chromsomes
(doubled genetic
material)
Meiosis Animation
Meiosis II
 (2 division):
Reduces the
genetic
material
 Result: _all
genetically
different

MEIOSIS ALLOWS FOR LOTS OF VARIATION
(DIFFERENCES)
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Variation as a result of:
Crossing Over: a part of
one chromosome can
switch places with the
same part another
homologous chromosome .
 Random Assortment: of
chromosomes allows a
mix of chromosomes from
both parents
 Random Fertilization :
of any egg by any sperm
allows for lots of variation

PROBLEMS WITH MEIOSIS:
Mutations: changes in
the DNA before meiosis
or mitosis begins
 Nondisjunction:
homologous
chromosomes do not
separate resulting in
one too many or one too
few chromosomes
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Ex. Down syndrome :
trisomy 21
Karyotype- a picture of
the chromosomes
NONDISJUNCTION
COMPARISON OF MITOSIS AND MEIOSIS
TICKET OUT THE DOOR
How many cells are produced as a result of
Meiosis?
 If a parent cell has 4 chromosomes and goes
through MEIOSIS, how many chromosomes
would the daughter cells contain?
 Meiosis is uses for (sexual or asexual)
reproduction?
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