I can:
Thursday
May 25, 2017

Agenda
(10) Catalyst
(15) Review Cell Cycle
(20) Quizlet Live!
(25) Trashketball (or more
Quizlet Live
(15) Daily Quiz
review the processes of mitosis and
meiosis
Catalyst
1. Grab your computer and go
to goo.gl/WQRt54 (type
EXACTLY as is)
2. Familiarize yourself with the
flashcard decks and review
options.
HW: BRF #28-38 (no #31)
135 Things… (June 2)
Biology Released Form
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Biology Released Form
If you got…
•
•
•
•
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~0-4 right  Level 1
~5 right  Level 2
~6 right  Level 3
~7-8 right  Level 4
~9 right  Level 5
The cell cycle is the series of four events that cells go
through as they grow and divide.
G1 phase
S phase
G2 phase
M phase
The cell cycle is the series of four events that cells go
through as they grow and divide.
G1 phase
Gap 1 phase: Cells
grow in size and
make new proteins
and organelles.
The cell cycle is the series of four events that cells go
through as they grow and divide.
S phase
Synthesis phase:
DNA replication
occurs
The cell cycle is the series of four events that cells go
through as they grow and divide.
G2 phase
Gap 2 phase: Cell
prepares for
mitosis.
The cell cycle is the series of four events that cells go
through as they grow and divide.
M phase
Mitotic phase: Cell
divides. Consists of 2
parts:
• mitosis – nucleus
divides
• cytokinesis –
cytoplasm and cell
membrane divide
The cell cycle is the series of four events that cells go
through as they grow and divide.
G1 phase
S phase
G2 phase
The first 3 stages of the cell
cycle are called interphase. The
cell spends most of its time in
interphase.
Mitosis is the process by which a cell divides itself one
time to produce 2 identical daughter cells.
• occurs in 4 phases
(before mitosis)
Prophase
Metaphase
Anaphase Telophase
Interphase
• DNA condenses
• chromosomes
into
line up across
• sister
the chromatids
• chromosomes begin
G1 phase
chromosomes
center of the cell
split and move
to loosen
G2 phase
• nuclear envelope
• spindle fibers attach to apart to •opposite
nuclear envelope
S phase
breaks downchromosomes
ends of the reforms
cell
DNA appears in various forms at different stages of
the cell cycle.
During interphase, the
DNA in a cell is in a loose
form called chromatin.
During the S phase, DNA is
duplicated, and each copy of DNA
is held together at an area of the
DNA called the centromere. Each
copy is called a sister chromatid.
A chromosome is a
tightly coiled molecule of
DNA packaged with
proteins. Only appears
during mitosis.
Sexual reproduction involves the contribution of genetic
material from two parents, and results in….
genetic
variation!
intercourse
Human Chromosome Number
Human body cells contain 2 copies of each of 23
chromosomes.
• 1 copy comes from each parent
copy from mom
• 2 copies = diploid (2n) copy from dad
Each set of chromosomes
is homologous – they are
the same size and contain
the same information
chromosome 19
Human Chromosome Number
Human body cells contain 2 copies of each of 23
chromosomes.
• 1 copy comes from each parent
copy from mom
• 2 copies = diploid (2n) copy from dad
Each set of chromosomes
is homologous – they are
the same size and contain
the same information
After doubling during the S phase, the
homologous chromosomes now form tetrads.
chromosome 19
Human Cell Type
Somatic Cells
Gametes
• body cells
• diploid (2n) = 2 copies of 23
chromosomes
• made by mitosis
• egg and sperm
• haploid (1n) = 1 copy of 23
chromosomes
• made by meiosis
Meiosis (aka reduction division) is the process in which
gametes are made.
Just like mitosis, except…
each cell divides two times
each cell produces 4 daughter cells
cells produced are haploid, not diploid
each cell produced is different from the parent
There are many ways in which meiosis results in genetic
variation, or different combinations of DNA.
1. Crossing-over
During prophase I of meiosis, homologous chromosomes pair up
to form a tetrad. Chromatids then cross over each other, and the
crossed sections are exchanged. This results in new combinations
of genes (DNA).
There are many ways in which meiosis results in genetic
variation, or different combinations of DNA.
2. Random (or Independent) Assortment
Chromosomes are separated into gametes randomly. That is why
you inherit traits by chance, and you get a mix of traits from each
parent.
There are many ways in which meiosis results in genetic
variation, or different combinations of DNA.
3. Mutation
Sometimes there is a mistake in the DNA that is not caught.
There are many ways in which meiosis results in genetic
variation, or different combinations of DNA.
23
46
23
4. Fertilization
Reproduction that requires 2 parents results in variation because
any combination of egg and sperm is possible. Fertilization (when
an egg and sperm combine) restores the correct chromosome
number.
There are many ways in which meiosis results in genetic
variation, or different combinations of DNA.
5. Nondisjunction
Nondisjunction is when chromosomes don’t separate correctly in
meiosis. It leads to the wrong number of chromosomes. It results
in genetic disorders like Down Syndrome.
The genetic variation produced by meiosis ensures that
there is a wide variety of traits in offspring.
QUIZLET LIVE!
It’s time for…
Trashketball!
Write On Your Board
What type of cell are egg and sperm? (gamete
or somatic)
gametes
Write On Your Board
What type of cell is a skin cell? (gamete or
somatic)
somatic cells
Write on Your Board
What type of cell is a gamete (diploid or
haploid), and how many chromosomes does it
contain?
haploid, 23
Write on Your Board
What type of cell is a somatic cell (diploid or
haploid), and how many chromosomes does it
contain?
diploid, 46
Write on Your Board
What kind of cell is made by mitosis?
somatic cells
Write on Your Board
What kind of cell is made by meiosis?
gametes
Write on Your Board
A skin cell has 36 chromosomes. How many
chromosomes are in the same organism’s
sperm?
18
Write on Your Board
A nerve cell has 102 chromosomes. How many
chromosomes are in the same organism’s eggs?
51
Write on Your Board
An egg cell has 48 chromosomes. How many
chromosomes are in the same organism’s liver
cell?
96
Write on Your Board
A sperm cell has 22 chromosomes. How many
chromosomes are in the same organism’s bone
cells?
44
Write on Your Board
Mitosis or meiosis:
produces 2 cells
mitosis
Write on Your Board
Mitosis or meiosis:
produces cells that are identical to
the parent
mitosis
Write on Your Board
Mitosis or meiosis:
produces cells that are genetically
different from the parent
meiosis
Write on Your Board
Mitosis or meiosis:
produces 4 cells
meiosis
Write on Your Board
Mitosis or meiosis:
chromosome # is the same as
parent
mitosis
Write on Your Board
Mitosis or meiosis:
has half as many chromosomes as
parent cell
meiosis
Write on Your Board
Mitosis or meiosis:
increases genetic diversity
meiosis
Write on Your Board
Mitosis or meiosis:
chromosome number is divided in
half
meiosis
Write on Your Board
Mitosis or meiosis:
results in clones
mitosis
Write on Your Board
Mitosis or meiosis:
crossing-over occurs
meiosis
Write on Your Board
Mitosis or meiosis:
asexual reproduction
mitosis
Write on Your Board
Mitosis or meiosis:
makes gametes
meiosis
Write on Your Board
Mitosis or meiosis:
part of sexual reproduction
meiosis
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Mitosis or meiosis:
makes somatic cells
mitosis
Write on Your Board
Mitosis or meiosis:
occurs in reproductive organs
(ovaries, testes)
meiosis
Write on Your Board
Mitosis or meiosis:
occurs in somatic cells
mitosis
Write on Your Board
What does crossing-over result in?
different combinations
of DNA (genes)
What stage?
What stage?
What stage?
What stage?
What stage?
The cell spends most of its time in…
what stage?
Which is a result of mitosis?
A. four sex cells
B. four haploid cells
C. two diploid daughter cells
D. two haploid daughter cells
2 pts.
Why is cytokinesis important in cell division?
A. The cell grows
B. The nucleus divides
C. Chromosomes are duplicated
D. The cytoplasm and cell membrane split,
forming two daughter cells
2 pts.
Before the process of mitosis can start,
which must occur?
A. DNA replication
B. RNA transcription
C. Protein translation
D. Microtubule formation
2 pts.
Which is most likely occurring when animal
cells undergo mitosis at an abnormally high
rate?
A. Gametes are being produced
B. Cells are undergoing cytolysis
C. Haploid cells are being created
D. Cancerous tumors are developing
4 pts.
Some species of starfish can reproduce by
breaking off an arm or splitting in half. Each
arm or half then becomes a whole new
organism genetically identical to the parent.
Which type of cell division occurs in this
process?
A. Meiosis
B. Mitosis
C. Budding
D. Conjugation
4 pts.
Why does meiosis promote genetic
variability?
A. Meiosis undergoes one cell division
producing diploid cells.
B. Meiosis undergoes one cell division
producing haploid cells.
C. Meiosis undergoes two cell divisions
producing diploid cells.
D. Meiosis undergoes two cell divisions
producing haploid cells.
4 pts.
An individual has three number 21
chromosomes. Which is most likely the
cause?
A. Disjunction
B. Crossing over
C. Gene mutation
D. Nondisjunction
4 pts.
Which explains the significance of meiosis in
the development of gametes?
A. Meiosis produces identical daughter cells.
B. Meiosis reduces the chromosome number
by one-half.
C. Meiosis combines an egg and a sperm to
form a zygote.
D. Meiosis increases the number of offspring
an organism can produce.
4 pts.
What is a result of crossing over during
meiosis?
A. Genetic variation
B. Extra chromosomes formed
C. Loss of chromosomes
D. Production of gametes
4 pts.
How does crossing over contribute to
greater genetic diversity?
A. It results in the exchange of proteins.
B. It produces new combinations of alleles.
C. It reduces the number of chromosomes in
each cell.
D. It separates the chromosomes at the
centromeres.
6 pts.
During which actions can an exchange of
genetic information occur during meiosis,
rather than during mitosis?
A. assortment and alignment
B. alignment and crossing over
C. crossing over and replication
D. assortment and crossing over
6 pts.
Meiosis produces cells in the haploid state.
In which process is the chromosome number
restored to the diploid state?
A. ovulation
B. fertilization
C. nondisjunction
D. spermatogenesis
6 pts.
Which best describes the purpose of sexual
reproduction?
A. to produce offspring that are nonviable
B. to produce offspring that are genetically
identical
C. to produce offspring that exhibit greater
genetic variations
D. to produce offspring that are genetically
identical to their parents
6 pts.
Nondisjunction during meiosis results in an
abnormal number of chromosomes in one or
more gametes. In some cases of nondisjunction,
a single chromosome fails to separate. In
others, none of the chromosomes separate.
Suppose an egg is produced in which none of
the chromosomes separate during meiosis II.
What is the chromosome number of the zygote
that results if this egg is fertilized by a normal
sperm?
A. 1n
B. 2n
C. 2n+1
D. 3n
6 pts.
The skin cells of an adult female rat has 40
autosomes and 2 sex chromosomes. A
healthy egg cell would contain which
number and type of chromosomes?
A. 20 autosomes and 1 X chromosome
B. 20 autosomes and 1 Y chromosome
C. 40 autosomes and 2 X chromosomes
D. 40 autosomes and 2 Y chromosomes
6 pts.