Download Cell Cycle Notes 16

Cells & Heredity Unit- The Cell Cycle
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Cells pass through different stages in their life cycle.
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The cell cycle starts when a cell is ___________ and ends when the cell ___________ to
make new cells.
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Before division, the cell makes a copy of its ________ that is stored in its chromosomes.
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Prokaryotic and Eukaryotic cells have different processes for cell division.
★ Prokaryotic Cell Cycle and Division
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Prokaryotes are a _________ cell with no organelles and their DNA is found on one
__________________ chromosome.
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Prokaryote cells ___________ using a simple process
called binary fission.
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Steps:
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DNA is _______________
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Cell ___________ and splits in half
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End result= 2 _______________ cells
★ Eukaryotic Cell Cycle & Division
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Cell division is more ______________ in eukaryotic cells.
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Occurs in 3 stages
1. Interphase- DNA ____________
2. Mitosis- Nucleus ______________
3. Cytokinesis- Cytoplasm ____________ and the cell divides
★ Interphase- the ______________ stage of the cell cycle
1. Growth phase 1 (G1)
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The cell ____________ rapidly
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Duplicates its ______________
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Cell spends ___________ of its lifetime in this phase
2. Synthesis phase (S)
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The cell copies its ______. This is DNA replication. This
makes a copy of each _________________.
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The 2 copies are called __________ chromatids and
attach at a ____________ point called the centromere.
3. Growth phase 2 (G2)
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The cell ____________ more and gets ready to divide.
★ Mitosis
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division of the ____________ including the chromosomes
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occurs in ____________ phases
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produces 2 genetically ______________ cells
★ Prophase- Prepare
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Sister _______________ have formed
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The nuclear ______________ breaks down
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Fibers called ____________ form to help the chromatids move.
★ Metaphase- Middle
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Sister chromatids line up in the _____________ of the cell
★ Anaphase- Away
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Spindle fibers ________ the sister chromatids toward the
opposite poles of the cell.
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This gives each pole a complete set of _______________.
★ Telophase- Two nuclei
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The chromosomes _______________
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New nuclear _________________ form
★ Cytokinesis- when the cell ______________
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This stage overlaps with the last step in mitosis, telophase.
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The cytoplasm _______________
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In animal cells- a cleavage ____________ forms and
separates the daughter cells
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In plant cells- a cell __________ divides the cell walls of the
daughter cells
★ Cell Feedback
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Cell cycle is controlled by ________________.
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When the cell is ___________ and healthy, the proteins in the cell get a “green light”
and the cell starts to copy its organelles and chromosomes.
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If there is a DNA ________________, the proteins that control cell division may not
control the cell properly.
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This can cause Cancer- uncontrolled ______________ of cells.
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DNA mutations can cause cells to speed up the cell ___________ or cause cells to never
stop dividing.
★ Reproduction
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Reproduction is how organisms produce ______________.
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There are two types of reproduction: _____________ or _______________
★ Chromosomes
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A chromosome consists of DNA and protein molecules coiled together.
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_______________ shape in prokaryotes
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________________ shape in eukaryotes
Humans have ___________ pairs of chromosomes. The last pair determine our ______.
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XX = _____________
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XY = _____________
★ Asexual Reproduction
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Asexual reproduction is simpler than sexual reproduction.
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It involves just one ______________.
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The offspring are genetically ______________ to each other and to the parent.
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All __________________ and some eukaryotes reproduce this way.
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There are several different methods of asexual reproduction including binary fission,
fragmentation, and budding.
★ Binary fission
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occurs when a parent cell simply ___________ into two daughter cells
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___________ reproduce this way
★ Fragmentation
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occurs when a _______________ breaks off from a parent organism
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the piece develops into a new organism
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______________ can reproduce this way
★ Budding
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occurs when a parent cell forms a ____________________ bud
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the bud stays attached to the parent while it ______________ and develops
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it ______________ away from the parent only after it is fully formed
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_______ can reproduce this way
★ Sexual reproduction
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Is more complicated
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It involves two ____________
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Special cells called gametes (sex cells) are produced by the parents that have
___________ of the chromosomes.
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In humans, a gamete produced by a _____________ parent is called an egg,
while a gamete produced by a ____________ parent is called a sperm.
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An offspring forms when two gametes _____________.
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The union of the two _____________ is called fertilization.
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The ____________ cell that forms when two gametes unite is called a zygote.
★ Chromosome Numbers
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In species with sexual reproduction, each ____ cell has two copies of each chromosome.
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The number of ___________ types of chromosomes
is called the haploid number.
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Ex: human beings have 23 different chromosomes. Each body cell contains two
of each chromosome, for a total of 46 chromosomes.
In humans, the haploid number is _______.
The number of chromosomes in normal ________
cells is called the diploid number. The diploid
number is twice the haploid number.
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In humans, the diploid number is two times
23, or _______.
★ Homologous Chromosomes
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The two members of a given pair of chromosomes are called
homologous chromosomes.
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We get one of each homologous pair, or 23 chromosomes,
from our ___________. We get the other one of each pair, or
23 chromosomes, from our ____________.
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A gamete must have the _________ number of
chromosomes. That way, when two gametes unite, the
zygote will have the ____________ number.
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How are haploid cells produced? The answer is ___________.
★ Meiosis
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Meiosis is a special type of cell division that
produces ____________ (sex cells).
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It produces haploid __________ cells.
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Cells prepare for meiosis by replicating their
__________.
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Next they go through ___________ divisions,
meiosis I and meiosis II.
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Meiosis I and meiosis II each have ___________ phases: prophase, metaphase,
anaphase, and telophase.
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This results in _________ haploid daughter cells.
★ Advantage of Asexual Reproduction
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Asexual reproduction can happen very _____________.
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Under ideal conditions, 100 bacteria can divide to produce millions of bacteria in
just a few hours!
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Most bacteria don’t live under ideal conditions. Even so, rapid reproduction may
allow asexual organisms to be very successful.
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They may crowd out other species that reproduce more slowly.
★ Advantages of Sexual Reproduction
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Sexual reproduction is typically ________. However, it also has an advantage. Sexual
reproduction results in offspring that are all ______________ different. This can be a big
plus for a species. The ______________ may help it adapt to changes in the
environment.
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How does genetic variation arise during sexual reproduction? It happens in three ways:
crossing over, independent assortment, and the random union of gametes.
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Crossing over occurs during prophase of meiosis I. The paired chromosomes
exchange bits of DNA. This _____________ their genetic material.
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Independent assortment occurs during metaphase of meiosis I. Chromosomes
line up ______________ and which ones end up together at each pole is a
matter of chance.
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The union of gametes occurs _____________. In sexual reproduction, two
gametes unite to produce an offspring. Which two gametes is a matter of
chance. Due to these sources of variation, each human couple has the potential
to produce more than 64 trillion unique offspring. No wonder we are all
different!