Cell Division (Handout) Flashcards
process by which cells
reproduce themselves
cell division
Cell division enables multicellular
organism
to grow and develop
to replace worn out or damaged tissues
cell division consists of two activities:
karyokinesis
cytokinesis
nuclear
division
karyokinesis
cytoplasmic
division
cytokinesis
- two kinds of nuclear cell division:
mitosis
meiosis
a cycle that a cell
undergoes that the cell undergoes
that a time it is formed until it
prepares itself for cell division
cell cycle
molecules synthesized in G1
RNA
proteins
- 3 types of RNA molecules:
rRNA
tRNA
mRNA
how many hydrogen bonds
between adenine and thymine
2 bonds
how many hydrogen bonds
between cytosine and guanine
3 hydrogen bonds
most critical stage of the
cell cycle
s stage
arranged to be
spindle fibers
microtubules
binding sites for
spindle fibers
kinetochore
a protein structure that connects chromosomes to spindle microtubules during cell division.
kinetochore
come
from centrioles attach to kinetochore
kinetochore microtubule
grow
outward but do not attach to
kinetochore
non kinetochore microtubule
radiate outward,
important in the stability of the
location of centrioles
aster microtubule
– cells divide how many times
in mitosis
once
cells divide how many times
in meiosis
twice
meiosis I is also
called this
reduction division
– meiosis II is
called this
equatorial division
homologous
chromosomes (1-22nd pairs)
autosomes
– determines the sex of the
child
father
can detect a person’s
genetic defect
karyotyping
also known as down
syndrome
trisomy 21
spermatogenesis/oogenesis
gatemogenesis
main organ of the male
reproductive system
testes
immature cells (2n)
in sperms
spermatogonia
spermatogonia undergo
what to become a primary
spermatocyte
mitosis
after undergoing
mitosis has the complete set of
chromosomes
spermatocyte
after undergoing
mitosis has the complete set of
chromosomes
secondary spermatocyte
the primary spermatocyte
undergoes this to become the
secondary spermatocyte
meiosis I
the secondary
spermatocyte undergoes this to
become the early spermatid
meiosis II
– number of chromosomes of
a early spermatid
haploid
early spermatid
undergoes this to become a late
spermatid
maturation
the late spermatid
undergoes maturation to become
this
spermatozoa
spermatogenesis ratio
1:2:4
- 1 primary spermatocyte > 2
secondary spermatocyte > 4
spermatozoa
primary reproductive
organ of females
ovaries
prior to birth, the
female gametes are these
oogonium (2n)
during
childhood, the ovary of a female child
has this
primary oocyte
– each month the primary
oocyte undergoes this to become a
secondary oocyte
meiosis I
this is the stage
where the egg is released
secondary oocyte
contains half the
number of chromosomes (n)
first polar body
when the egg meets
the sperm, the secondary oocyte
undergoes meiosis II when this
happen
fertilization
when the secondary oocyte is
fertilized by a sperm this forms
ootid
as a result of
meiosis II in oogenesis, this can form
second polar bodies
ratio in oogenesis
1:2:4
ratio of viability in oogenesis
1:1:1
production of sperm
occurs when
every day
production of egg cells
occurs when
monthly
study oogenesis labels
+1
a series of activities through which a cell passes from the time it is formed until it
reproduces
cell cycle
- last for about 90% of the cell cycle
cell cycle
§ referred to as the “resting stage” of the cell
interphase
it is during this stage that the replication of DNA, centrosomes, and
centrioles occurs and the RNA and protein needed to produce
structures required for doubling all cellular components are
manufactured
interphase
§ three distinct periods of interphase:
G1
G2
S
during which cells are
engaged in growth, metabolism, and the production of
substances required for DNA synthesis and cell division
G1 (growth period)
highly changeable ranging from non-existent in
rapidly dividing cells to days, weeks, or years;
however, it usually takes 8-10 hour
G1
cells that are intended to never divide again are
permanently arrested in this phase
g1 phase
most nerve cells are in this state because after about
6 months of development they become permanent
cells of the central nervous system
g1 phase
is the period of interphase during
which chromosomes are replicated (Figure 6.2)
s period
ü during DNA ___ , its double helical structure
partially unwinds and the two strands separate at the
points where hydrogen bonds join base pairs.
replication
ü during DNA replication, its double helical structure
partially unwinds and the two strands separate at the
points where ___ ____ join base pairs.
hydrogen bond
each exposed base then picks up a
complementary base
S phase takes about __ hours
6-8
once a cell goes through the S-phase, it is committed
to enter
cell division
– the mitochondria divide and the cell continues to
grow in preparation for cell division
what phase
g2 period
since the _-phases are stages when there are no
events related to chromosomal replication, they are
thought of as gaps or interruptions in DNA synthesis
G
karyokinesis (mitosis) is divided into
prophase
metaphase
anaphase
telophase
s finalizes cell division
cytokinesis
the time required for ___differs with the kind of cell, its location
and other factors such as temperature
mitosis
mitosis and takes cytokinesis about
1-2 hours
- somatic “body” cell division
mitosis
a parent cell divides once to produce two identical cells called
daughter
the process ensures that each daughter cell has the same number and kind of
chromosomes as the original parent cell (diploid)
mitosis
study mitosis phase page 4
+1
this kind of cell division allows growth of multicellular organisms, asexual
reproduction, and wound healing
mitosis
the chromatin condenses and shortens into chromosomes
prohpase
since DNA replication takes place during interphase, each prophase
chromosome contains a pair of identical double-stranded DNA
molecules called
chromatids
§ each chromatid pair is held together by a small spherical body called
a __that is required for the proper segregation of
chromosome
centromere
attached to the outside of each centromere is a protein complex
known as
kinetochore
the nucleoli disappear, and RNA synthesis also stops, and the nuclear
envelope breaks down and is absorbed in the cytosol
prophase
a centrosome and its centrioles each move to opposite poles of the
cell and as they do so the centrioles start to form th
mitotic spindle
as the mitotic spindle continues to develop, three types of
microtubules form:
non kinetochore microtubule
kinetochore microtubule
aster microtubule
grow from centrosomes,
extend inward, but do not bind to kinetochores
non kinetochore microtubule
grow from centrosomes, extend
inward, and attach to kinetochores
kinetochore microtubule
grow out of centrosomes but radiate
outward from the mitotic spindles
aster microtubule
is the attachment site for chromosomes and also distributes
chromosomes to opposite poles of the cell
spindl
by late prophase the chromosomes move towards th
equator of the cell
the period when maximum condensation of chromosomes is very
evident
metaphase
the centromeres of the chromatid pairs line up at the exact center of
the mitotic spindle; this midpoint region is called the
metaphase plate
equatorial plain region
§ characterized by the splitting and separation of centromeres and the
movement of the two sister chromatids of each pair towards the
opposite poles of the cell
anaphase
the sister chromatids are referred to as
daughter chromosomes
the movement of the chromosomes is due to the shortening of
___microtubules and elongation of the ___
microtubule
kinetochore
nonkinetochore
§ begins as soon as chromosomal movement stops
telophase
§ opposite of prophas
telophase
the identical sets of chromosomes at the opposite poles of the cell
uncoil and revert to their threadlike ___form.
chromatin
____ microtubules disappear, and ___
microtubules elongate even mor
kinetochore
nonkinetochore
§ a new nuclear envelope reforms around each chromatin mass
telophase
new nucleoli reappear in the daughter nuclei and mitotic spindle
breaks up
telophase
- division of the parent cell’s cytoplasm and organelles
cytokinesis
occurs during the telophase stage with formation of the ___ ___(a slight
indentation of the plasma membrane extends around the center of the cell)
cleavage furrow
the ___ gradually deepens until opposite surfaces of the cell make contact and the
cell is split in two
cleavage furrow
when cytokinesis is complete, ___ begins
interphase
- the result of cytokinesis is ___ separated daughter cells, each with separate portions
of cytoplasm and organelles and its own set of identical chromosomes
two
- reproductive “gamete” cell division
meiosis
- a parent cell divides twice producing four haploid nuclei
meiosis
can exchange genetic material before being
separated, therefore the daughter cells are genetically different from the parent cell
(and from each other)
homologous chromosomes
- the mechanism by which gametes (sex cells) are produced, this is the basis of sexual
reproduction
meiosis
without ___, the number of chromosomes of asexually reproducing species
would be doubled in each generation
meiosis
two successive divisions of meiosis
meiosis I and II
also called Reduction Division since the number of chromosomes in a cell is
halved (2n → n)
meiosis I
preceded by interphase apparently identical as that of mitosis, DNA and
organelles are duplicated and stored ATP is used
meiosis I
stage of meiosis I
prophase I
metaphase I
anaphase I
telophase I
prophase I is further divided into the following substages:
leptonema
zygonema
pachynema
diplonema
diakinesis
“thin threads”
leptonema/leptotene
ü chromosomes appear like “beads-on-a-string”
leptonema
initiation of homology search
leptonema
“yoked threads”
zygonema
condensation continues in meiosis I
zygonema
“rough pairing” – initial alignment of homologous
chromosome
what stage of meiosis I
zygonema
formation of bivalents (# of bivalents = n)
zygonema
= “thick threads”
pachynema
homologous chromosomes are already distinguished
under the microscope
pachynema
– intimate pairing of homologous
chromosomes
synapsis (pachynema)
ü four sister chromatids are evident and form a tetrad
pachynema
study meiosis I label (page 8)
+1
e = ‘double threads”
diplonema
one or more areas of
the non-sister chromatids remain in contact; sites of
crossing over (genetic exchange between maternal
and paternal chromosomes)
chiasmata
= “moving apart”
diakinesis
chromosome separation proceeds but as this
happens, the chiasmata move towards the end of
each tetrad
what phase
diakinesis
what process where chromosome separation proceeds but as this
happens, the chiasmata move towards the end of
each tetrad (
diakinesis
ü disintegration of nucleolus and nuclear membrane
what phase in meiosis I
diakinesis
ü centromeres of each tetrad attach to mitotic spindle
what phase in meiosis I
diakinesis
maximum condensation of chromosomes is attained
Ø terminal chiasmata of each tetrad are visible and appear to be
the only factor holding the non-sister chromatids together
metaphase I
Ø movement of homologous chromosomes to metaphase plate
metaphase I
Ø tetrads separate and dyads move towards opposite poles
anaphase I
Ø new nuclear membrane reforms
Ø nucleus enters into a short interphase
Ø some cells proceed directly to Meiosis II
telophase I
o also called Equatorial Division since the haploid cells produced by meiosis I
divide producing 4 haploid cells that are genetically different from one
another
equatorial division
very similar to mitosis in that it results in the separation of sister chromatids
meiosis II
each dyad is made up of two sister chromatids joined
together by a common centromere
prohpase II
Ø alignment of centromeres at metaphase plate in meiosis II
metaphase II
study mitosis and meiosis figure page 10
+1
Ø splitting of centromeres and movement of monads towards
opposite poles of the cell
anaphase II
monads reach opposite poles
telophase II
Ø nucleolus and nuclear membrane reform
Ø chromosomes uncoil and become inconspicuous; cytokinesis
occurs
telophase II
no. of daughter cells formed per cycle (mitosis vs meiosis)
two
four
