Chapter 8: The Cell Cycle Flashcards
cell division is used for?
- reproduction
- growth
- regeneration
unicellular organisms use cell division primarily for
reproduction
in multicellular organisms cell division is important to
growth and repair of tissues
What are the four events that must occur for cell division?
- reproductive signal
- replication
- segregation
- cytokinesis
What is a reproductive signal?
a signal that initiates cell division
Segregation refers to…
the distribution of DNA into the two new cells
What is cytokinesis?
the separation of the two new cells
In prokaryotes, what results in two new cells?
binary fission
What are the signals for replication of prokaryotes?
external factors
What two types of external factors signal for binary fission?
- nutrient concentration
2. environmental conditions
For many bacteria what speeds up the division cycle?
an abundant supply of food
Explain the 3 steps in binary fission
- a single circular chromosome replicates and separates
- cytokinesis
- new cell wall materials are synthesized -> separation of two cells
What happens during cytokinesis of binary fission
protein fibers form a ring and pinch off the plasma membrane
single-cell eukaryotes replicate by
budding
complex eukaryotes originate from
a single cell, the fertilized egg (zygote)
complex eukaryotic cells results from the union of….
gametes containing genetic material from both parents
What are the two cell types?
- germ cells
2. somatic cells
germ cells produce
gametes
gametes only contain…
one set of chromosomes
A haploid number of chromosomes is=
1n
fertilization is when…
two haploid gametes fuse
-female egg and male sperm
fertilization forms a
diploid zygote
a diploid zygote only contain…
2n
gametes are specialized for..
reproduction
gametes reside in
primary sex organs
- testis
- ovaries
somatic cells are NOT
specialized for reproduction
somatic cells contain…
23 homologous pairs of chromosomes with corresponding genes
each parent contributes one
homolog (23 chromosomes)
meiosis occurs in
germ cells
meiosis produces
4 haploid (1n) daughter cells genetically diff. from each other and from parent cell
mitosis results in
2 identical diploid (2n) sister cells identical to the parent cell
most of the lifetime of a cell is NOT spent doing
cell division
the cell cycle are a series of events that
occur to produce two eukaryotic cells from one
What are the phases the cell cycle consists of?
1.
2.
What are the 3 sub-phases of interphase?
- G1
- S phase
- G2
G1 is located between
the end of mitosis and S phase
What occurs during the S phase?
DNA replicates; each chromosome is now a pair -> two sister chromatids
During G2…
the cell prepares for mitosis
interphase DOES NOT involve
mitosis
the cell remains in G1 until
a signal of replication is received
The M phase is where ______ and ______ occurs
mitosis and cytokinesis
Where does chromatin form?
forms when replicated DNA is complexed with proteins
What coats the DNA to make it more compact?
condensins
sister chromatids are held together by cohesions at the
centromere
what are histones?
proteins that attract phosphate groups of DNA
chromosomes that have histones causes the formation of
nucleosomes
How does chromatin appear during mitosis and meiosis?
coiled and condensed until chromatids move apart
kinetochores are
the area where microtubules attach to chromosomes
As DNA replicates the ______ doubles.
centrosome
centrosomes consist of
two centrioles
prophase is known as the ______ phase
preparation
during prophase cohesion _______ and ______ become visible
disappears
chromatids
during prophase _____ forms the centromere regions
kinetochores
microtubules form the
mitotic spindle
during prometaphase the nucleus
“disappears”
during prometaphase kinetochores attach to
the microtubules and push towards the equatorial plate
during metaphase the centromeres….
arrive at the equatorial plate
the centromere at the equator of the cell is critical for
equal division of chromosomes into daughter cells
during anaphase the sister chromatids
separate and move to opposite ends of the spindle
name two motor proteins
kinesin
dynein
motor proteins attach to
kinetochores and microtubules
during anaphase MT….
shorten pulling chromosomes toward poles
what are the four things that happen in telophase?
- spindle breaks down
- nuclear envelope reform
- chromosomes uncoil
- two daughter nuclei are formed with identical genetic information
cytokinesis is when
the cell membrane pinches off, separating the two newly formed daughter cells
how is cytokinesis distinguished in animal cells?
by the formation of a cleavage furrow
the cleavage furrow is formed by
actin filaments
cytokinesis distinguished in plant cells by the formation of
a cell plate
how is the cell plate formed?
vesicles containing the cell wall material align and then fuse
what are the two irreversible points of the cell cycle?
- replication of DNA
2. separation of sister chromatids
what two check point can put the cycle on hold?
- DNA checked for accuracy
2. cell is able to respond and make repairs
the cell cycle is the most highly controlled
physiological process
two things that happen during the G1/S checkpoint
- cell “divides”
2. primary external signal influence
what happens during the G2/M checkpoint?
- cell commits to mitosis
2. assesses success of DNA replication
what happens during the late metaphase (spindle) checkpoint?
ensures that all chromosomes are attached to the spindle
transitions of the cell cycle depend on what protein?
cyclin-dependent kinase (Cdk)
How is Cdk activated?
by binding to cyclin
the cyclin Cdk complex triggers the transition from
G1 to S
cyclin and Cdk act like
on/off switches
growth factors trigger
intracellular signaling systems
platelet-derived growth factor signals
cells at a wound site to divide
growth factor signals override…
controls that normally inhibit cell division
list 3 ways that cancer cells can be mutated
- make their own growth factor
- divide without a growth factor signal
- bypass the cell-death control system
cancer is known as
uncontrolled growth of cells
what are the two genes that can promote cancer when mutated?
- tumor-suppressor genes
2. proto-oncongenes
what is the function of the tumor-suppressor genes?
to stop the cell cycle if DNA is damaged leads to a repair that is stimulated
what are proto-oncogenes?
normal cellular genes that become oncogenes when mutated
what was the first tumor suppressor that was identified?
retinoblastoma
what is the break mechanism that launches cellular death?
p53 protein
asexual reproduction produces offspring that are
genetically identical to the parent
meiosis produces gametes that
differ genetically from the parents
what are the two different types of cells?
- somatic cells
2. germ cells
in somatic cells each parent contributes one
homolog
germs cells only contain
one set of chromosomes
in most animals which state dominates?
the diploid state
the sexual life cycle is made up of
meiosis and fertilization
in meiosis DNA is ONLY
replicated once
the nuclear divisions of meiosis occur during
meiosis I and meiosis II
meiosis ensures that each gamete has
a single full set of chromosomes
meiosis includes two rounds of
division
when does synapsis occur?
during early prophase I
synapsis occurs the formation of
synaptonemal complexes
tetrad/ bivalents
what is crossing over?
genetic recombination between non-sister chromatids
during crossing over homologues exchange
chromosomal genetic material
what is chiasmata?
the site of crossing over
the sister chromatids remain together until after
metaphase II
in meiosis II the sister chromatids may not be identical due to
crossing over
what are the two opportunities for diversity?
- crossing over
2. independent assortment
what are the three differences between meiosis I and mitosis?
- synapsis and crossing over
- sister chromatids remain joined throughout meiosis I
- homologous pairs separate randomly at anaphase I
