Chapter 7: The Cell Cycle and Cell Division Flashcards
Cells
basic components of life, self-contained biological processes
reproduction
Asexual Reproduction
super duper quick (think lightning or the flash)
really effective way of making new individuals
super popular
makes clones of the parent
only variation from mutation, so less variation
clones
genetically identical
dos Olivias salen
Mutations
alterations in the DNA caused by the environment or replication mistakes
Binary fission
used by most single-celled prokaryotes
means of reproduction
Mitosis
used by single-celled eukaryotes
produces fro genetically identical cells asexually
Sexual Reproduction
the fusion of two specialized cells called gametes
result in offspring with significant variation
uses meiosis
gamete
specialized cell
half of the genetic material as the parent cell
single set of chromosomes– one homolog from each pair
n chromosomes
haploid
Mesiosis
a process of cell division that results in daughter cells with only half of the genetic material of the original cell
random separation of genetic material so daughter cells are very different
differences lead to a better adapted organism lead to natural selection
Chromosome
a single molecule of DNA and associated proteins
somatic cells
body cells which are not specialized for reproduction
two sets of chromosomes in homologous pairs
homologous pairs
the pairs in which the two sets of chromosomes that somatic cells contain are organized into
have corresponding genetic information
zygote
the fused haploid gametes
diploid
2n chromosomes
fertilization
the fusing of two haploid gametes
Do all sexual life cycles involve meiosis?
yup
sometimes, just gamete then meiosis
some haploid becomes a haploid organism which eventually creates gametes
Haplontic organism sexual life cycle
protists, fungi, green algae
zygote is the only diploid cell in the life cycle
after formation, it immediately produces more haploid cells, generally spores (the dispersal units for the organism)
Alternation of generations
plants and fungi
meiosis creates haploid spores, they mitosis it up and produce a gametophyte
in flowering plants, there are super small (pollen and embryo sac)
in mosses, they are super big
gametophyte creates gametes by mitosis, which fuse to form the diploid zygote
the zygote mitosises it up and and creates a sporophyte
Diplontic organisms
animals, brown algae, fungi
gametes only haploid cells
mature or
What is the essence of sexual reproduction?
THE RANDOM SELECTION OF HALF OF THE DIPLOID CHROMOSOME SET to make a diploid
What needs to hPpen for cell division?
reproductive signal- initiates cell division and can come from inside or outside the cell
replication of DNA must occur
the DNA must be distributed to the two new cells
enzymes and organelles must be made and material needs to be added to the membrane
cytokinesis
the division of the cytoplasm
ori
the sort where replication of the circular chromosome started
The ORIgin of replication
ter
the site where replication ends
the TERminus of replication
True or false: In prokaryotes it is common to have 8 chromosomes
False, most prokaryotes have all of their genetic information on one chromosome
True or false: Most prokaryotes have circular chromosomes
true
Where does replication begin in Binary fission and what happens as it proceeds?
it begins near the center of the cell and as replication progresses the ori moves towards the ends of the cells
this process is driven by the binding of DNA to proteins that ensure its success
cytokinesis in binary fission
the actual division of a cell and contents
starts right after chromosome segregation
starts with a pinching in of the plasma membrane caused by the contraptions of fibers on the inside surface
as this pinching occurs, new cell wall materials are deposited, leaving two separate cells
Eukaryotic DNA replication
eukaryotes have like lots of chromosome, so each one follows a process akin to that in binary fission.
IN EUKARYOTES IT CAN ONLY OCCUR IN ONE STAGE IN THE CELL CYCLE
Eukaryotic DNA segregation
the chromosomes are all hanging out close together after replication and they must be separated so each daughter cell has a full lest after division
This is done by condensing them and pulling them to opposite ends of the cell
Cytokinesis in Eukaryotes
animals (just cell membrane) and plants (also cell wall) have different processes for cell division
Cell cycle
the period from one division to the next
eukaryotes- mitosis and cytokinesis (M phase)
and interphase
Interphase
the nucleus is visible typical cell stuff is happening
lasts from the end of cytokinesis to the start of mitosis
G1 S G2
G1
part of interphase gap 1 time varies, can last a ridiculously long time point of no return the cell is just being a regular cell
S
part of interphase
synthesis
DNA replication occurs here
G2
part of interphase
the cell is getting ready for mitosis (like making microtubulues and stuff like that)
gap 2
Mitosis
A SINGLE NUCLEUS GIVES RISE TO TWO DAUGHTER NUCLEI THAT EACH CONTAIN THE SAME NUMBER OF CHROMOSOMES AS THE PARENT NUCLEUS four phases Prophase Prometaphase Metaphase Anaphase Telophase
Prophase
start of mitosis
condensation of chromosomes
formation of mitotic spindle
Sister chromatids
the two identical strands that make up the X shaped DNA present after division
Centromere
the region that holds together the sister chromatids
kinetochores
special proteins that go on the centromeres, with one on each chromatid
karyotype
the number and sizes of the condensed chromosomes
Centrosomes
determine the orientation of the spindle apparatus
made of a pair of centrioles
determine the plance at which the cell divides/the spatial relationships between the new cells
serve as poles toward which the chromosomes move
centrioles
hollow tubes formed with nine triplets of microtubulues
9 by 3
Spindle
the micrtobules that come from the centrosome and from the poles
forms during prophase
Polar Microtubules
form the frame of the spindle and keep the two poles apart
Kinetochore microtubules
form after polar microtubules
attach to kinetochores on the chromosomes
ensure that the chromatids move to opposite sides
Daughter chromosomes
separated sister chromosomes
What is the central feature of mitosis?
separation of the daughter chromosomes
Prometaphade
nuclear envelope breaks down and the compacted chromosomes attach to the kinetochore microtubules
second stage of mitosis
Metaphase
chromosomes line up at the midline of the cell
third stage of mitosis
Anaphase
the chromatids separate and the daughter chromosomes move away from each other toward the poles
fourth stage of mitosis
What mechanisms move the chromosomes to the poles?
The kinetochores have a protein called cytoplasmic dyne in that acts as a molecular motor, using up atp and creating energy for the movement of chromosomes
the kinetochores also shorted to draw the microtubules towards them
Telophase
last stage of mitosis
occurs after the chromosomes have separated
nuclear envelope forms around each new set of chromosomes, nucleoli reform, the chromosomes become less compact, and the spindle disappears
two nuclei in one cell
Cytokinesis
division of the cytoplasm
final stage of cell reproduction
Cytokinesis in animal cells
starts with a furrowing of the plasma membrane
this is produced by a contractile ring and in made of microfilaments of actin and myosin, which interact to form a contraction
the microfilaments assemble rapidly
Cytokinesis in plant cells
Cell walls
after spindle break down, vesicles from the Golgi appear along the plane of cell division, about halfway between two daughter nuclei
these are sent along microtubules by kinesin and fuse to create a new membrane
they also contribute to a cell plate: the start of anew wall the will separate the two new cells
True or false: cell reproduction can go on continuously and definitely
falseeeee
if a single celled organism did that, it would like take over the environment and starve to death
Growth factors
stimulate cell division and differentiation
G1-S transition/G checkpoint
key point
R/restriciton point
point of no return
commits the cell to the cell cycle
What causes a cell to enter the S or M phases?
substances control these stages/ activate them
protein kinases
Cyclin-dependent kinases (Cdk’s)
protein kinases that bind to the protein cyclin
this causes the active site to be exposed #allosteric regulation
regulate at checkpoints
each is regulated by its own cyclin which is made at the right time and then broken down
What causes cyclin synthesis?
many things including growth factors
How do cdks work for the G1-S transition?
once they are activated, the phosphorylate the protein inhibiting/blocking the cell cycle, changing its structure and inactivating it
How many nuclear divisions are involved in meiosis?
two nuclear divisions
this brings the chromosome number down to the haploid number
How many times does the DNA replicate in meiosis?
once
The products of meiosis are…..
genetically different from one another and the parent
What are the goals of meiosis?
reduce the chromosome number from diploid to haploid
ensure that the haploid products have complete chromosomes set
generate genetic diversity
What are the two unique characteristics of meiosis I
homologous chromosomes come together and line up along their entire lengths
watch with envy green eyes mitosis because you don’t get to do that
Homologous chromosome pairs separate but the individual chromosomes (each with two sister chromatids) remain intact
meiosis two can look on and appreciate the awesome, but it can not join this cool group
True or false: meiosis I is preceded by an interphase with an S phase
true, gotta get that DNA replication
True or false, meiosis II is preceded by an interphase with an S phase
False, the sister chromatids separate in meiosis II, producing four cells each with half the number of chromosomes
True or false: the products of meiosis are genetically identical
false
the products are four haploid cells that are NOT genetically identical
Crossing over
Occurs in prophase I in meiosis I
homologous chromosomes pair up along lengths in a process called synapsis
these pairs last until the end of metaphase I
form tetrads
then the material gets all exchanged and stuffs
Tetrad
what the four chromatids form during crossing over
come from the chromosomes from the two partners in each homologous pair
Chiasma
attachment points
x shaped
during crossing over
keep them together when the chromosomes begin to repel one another
where genetic material is exchanged between nonsister chromatids
not visible until after crossing over starts
True or false: mitosis is shorter than meiosis
so false
mitosis takes so much less time
Independent Assortment
meiosis
another source of genetic diversity
which daughter a chromosome goes to during anaphase I is all chance
Having more or less chromosomes increasing genetic diversity
More
#independent assortment
The greater the number of chromosomes, the lower the probability of reestablishing the original parental combinations, and the greater the potential for genetic diversity
True or false: meiosis II is similar to mitosis
True
Nondisjunction
meiotic error
Homologous Chromosome pair fails to separate at anaphase II or pair of chromatids doesn’t separate at anaphase II
Aneuploidy
having an extra (trisomy) or missing a chromosome (monosomy)
incorrect #
Polyploidy
triploif ot tetraploid organisms or higher polyploid nuclei may form
many reasons
extrra DNA replication or no spindle in meiosis II
occurs naturally in some animals and lots of plants
triploid can’t undergo normal meiosis— infertile
Translocation
meiosis I
chromatids from non-homologous pairs can break and rejoin, resulting in translocation
Necrosis
type of cell death
cells are damaged by mechanical means or toxins or starved of oxygen or nutrients
often burst and spill their like inner stuffs all over the place
can cause inflammation
less common type of cell death
Apoptosis
genetically programmed series of events that result in cell death
Reasons for apoptosis in animal cells
- cell is no longer needed by organism (ex. no more webbed fingers in people)
- The longer cells live, the more prone they are to genetic damage that could lead to cancer (ex/ skin cells exposed to lots of stuff)
Steps of apoptosis
cell detaches from neighbors, hydrolyzes DNA into teeny tiny parts, and forms blebs that break up into cell fragments
surrounding living cells ingest that stuff, rest digested by lysosomes
Hypersensitive response
plants
defense involving apoptosis
undergo apoptosis at an infection site
Do plant cells form blebs like animal cells?
cell walls lget in the way
plant cells digest own cell contents in vacuole and release these digester bits into the vascular system
Caspases
enzymes
proteases that hydrolyze target molecules in a cascade of events
cell dies as they hydrolyze proteins
triggered by internal and external signals
Oncogene
cancer cells
come from normal positive regulators, but they are mutated to be overly active
make cancer cell divide more often
Tumor suppressors
negative regulators of the cell cycle in normal cells
inactive in cancer cells
