Biology Megan ch 12 The Cell Cycle

Cell division produces genetically _____ daughter cells

identical

What is the beginning point for a multicellular organism?

a single cell (that then divides into two)

What is the role of cell division in a single-celled organism?

new organisms (via cell division)

What are the 2 roles of cell division in multicellular eukaryotes?

(1) embryonic development (2) renewal and repair

T/F--cell division produces two daughter cells with identical genetic material

True (it is remarkably accurate)

Define "genome"

all the DNA in a cell

What makes up the genome of a prokaryote?

a single DNA molecule

What makes up the genome of a eukaryote?

several DNA molecules

What makes up a chromosome?

the DNA molecules in a cell (with 100s to 1000s of genes per chromosome)

What is the material that makes up eukarytic chromosomes?

chromatin

Chromatin is comprised of what two elements?

(1) DNA (2) protein

How many sets of chromosomes are found in somatic cells?

two sets (diploid or 2n)

What kind of cells have two sets of chromosomes?

somatic cells

How many sets of chromosomes are found in gametes?

half as many as the somatic cells (haploid or 1n)

What are two examples of gametes?

(1) eggs (2) sperm

What are the three components of cellular division?

(1) interphase (2) mitosis/karyokinesis (3) cytokinesis

Another way to ask the question of cellular division would be to divide it into 2 phases--name those. (instead of 3)

(1) interphase (2) mitotic phase (including cytokinesis in this)--see slide 9

During what phase of cell division does the cell grow and chromsomes duplicate?

interphase

During what specific part of interphase do the chromosomes replicate?

S phase

When a chromosome replicates, the duplicated chromosome consists of two ______ _______ joined by certain proteins. Name the proteins as well.

sister chromatids, cohesins

What is the term for the "waist" where the two sister chromatids meet?

the centromere

Once the two sister chromatids separate and move into the new nuclei, what are they then called?

chromosomes

What are the two components of eukaryotic cell division that come after interphase?

(1) mitosis/karyokinesis--where the genetic material divides (2) cytokinesis--the cytoplasm division

What different type of cell division is used by gametes?

meiosis

What are the two key differences between mitosis and meiosis?

(1) daughter cells are nonidentical (2) daughter cells contain half as many chromosomes as the parent cell

How much of the cell cycle is taken up by interphase?

90%

What are the three phases that make up interphase?

(1) G1 phase (gap/growth) (2) S phase (DNA synthesis) (3) G2 phase (gap/growth)

What happens during G1 and G2?

growth

What happens during S phase?

DNA synthesis (and growth also happens--see slide 10)

What 3 checkpoints are found in the cell cycle?

(1) G1 checkpoint (2) G2 checkpoint (3) M checkpoint

T/F the three checkpoints have both internal AND external regulation

True

What happens if the cell doesn't get a "go-ahead" signal at the G1 checkpoint?

the cell enters G0

What happens if the cell DOES get a "go-ahead" signal at the G1 checkpoint?

It proceeds in the cell cycle

What is vital at the M checkpoint to get a "go-ahead" signal?

the chromosomes have to be attached (looks like the signal is about prometaphase to metaphase? check with her)

What kinds of proteins are involved in the cell cycle control? 2 points

(1) cyclins (2) cyclin-dependent kinases

Where does the term cyclin come from?

their concentrations fluctuate cyclically in the cell (look at figure 12.16a--they rise during S and G2 and peak in M and flatten out by G1)

Name an important cyclin-kinase complex involved in cell cycle

MPF (maturation-promoting factor)--note that it rises when cyclin rises in figure 12.16a

Name the mitotic phases in order

prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis

What is a centrosome?

the microtubule organizing center of the cell (MTOC)

When does the centrosome duplicate/replicate?

during interphase

What is found within the centrosome?

a pair of centrioles

What are centrioles made of?

microtubules

If centrosomes duplicate/replicate during interphase, when do they migrate to opposite ends of the cell?

prophase/prometaphase

During G2--what is the status of the centrosomes and what is the status of the chromosomes?

(1) centrosomes are duplicated but at one pole (2) chromosomes are duplicated but uncondensed

During prophase, what is the status of the centrosomes and the chromosomes?

The centrosomes start to migrate toward the poles and the chromosomes condense into sister chromatids joined at the centromere.

What begins to form during prophase

the mitotic spindle

What is the mitotic spindle?

microtubules that control chromosomes movement during mitosis

What are the components of the mitotic spindle?

(1) the centrosomes (at opposite ends of the cell by end of prometaphase), (2) the aster (3) the spindle microtubules

What is the aster?

a radial array of microtubules that sticks out from the centrosome

The spindle microtubules are two kinds with two functions. Name the two kinds

Kinetichore and nonkinetochore microtubules

What is the function of kinetochore microtubules?

attach to the kinetochore (a protein complex at each centromere of the sister chromatids) to help move them

What is the function of the nonkinetochore microtubules?

they overlap from opposite poles and push against each other to make the cell enlongate

What happens to the nuclear envelope during prometaphase?

it fragments (so the kinetochore microtubules can now reach the kinetochores)

What happens during metaphase?

the chromosomes line up along the metaphase plate (middle of the cell)

What happens during anaphase?

sister chromatids separate and move toward the poles of the cell (they are now called chromosomes)

During anaphase, what important enzyme is needed to help the sister chromatids split apart?

separase

What does separase do during anaphase?

cleave the cohesins

During anaphase as the chromatids move, what end of the kinetochore microtubule shortens?

the kinetochore end (it spits off tubulin subunits)

What protein helps "walk" the chromosome along the microtubule during anaphase?

motor proteins (see fig 12.9)

What happens in telophase?

cytokinesis, the spindle disassembles, the nuclear envelope and the nucleolus form

What different ways does cytokinesis happen in an animal vs a plant cell?

(1) animal--cleavage furrow (2) plant--cell plate

What is the kind of cell division for prokaryotes e.g. bacteria?

binary fission

In binary fission, where does chromsome replication begin?

the origin of replication

In binary fission, after chromosome replication completes, what two things happen?

(1) the daughter chromosomes move apart (2) the plasma membrane pinches in and divides into two cells (I don't know what to ask on figure 12.13--just look at it)

In what 3 ways can cancer cells be abnormal?

(1) ignore normal signals (2) don't need growth factors (3) have abnormal cell cycle controls

What is the term for a cell that can divide indefinitely?

they have undergone transformation

What is different about a benign tumor?

the abnormal cells are at the original site but they don't invade/spread

What is different about a malignant tumor?

they can invade/spread cells (metastasize to other sites and make new tumors)

What have most cancer cells lost?

the ability to repair DNA damage

What is the mechanism to many cancer drugs (chemotherapy)?

they target the cell cycle

Because many chemotherapy drugs target the cell cycle, what other tissues do they tend to affect?

rapidly dividing tissue (like hair--you lose it, nails--they get brittle, GI tract--nausea and diarrhea)