Review Questions for Cell Cycle, Mitosis, Meiosis, Genetics
The Cell Cycle and Mitosis:
What are the basic phases of the cell cycle?
Interphase: the growth and preparation of the cell for duplication/division.
M (mitosis): Division of the cell and cytoplasmic content (11.5 hours)
What are the stages of Interphase and what happens during each one? What is the G phase? 0
G1: lots of growth, enlargement of the cell. Protein synthesis. Huge increase in volume. Lots of
transcription/translation. Has to enlarge membrane and fill contents of the cell. Longest
phase (89 hours). Anabolism.
S phase: Growth and DNA replication takes place. Each strand is replicated (anabolic). Pretty
long (78 hours)
G2: completion of certain growth aspects such as duplication/division of centrioles. More
specific things get ready for cell division (mitosis). Relatively short phase.
G0: quiescent phase. Adults can go into this phase.
Why is the regulation of the cell cycle important and what are some of the ways this happens?
It makes sure that the cell is not replicating mutated or damaged cells, makes sure that it is replicating enough/not too much.
During G1, cells respond to various internal and external signals.
Internal: checking for cell size, readiness for DNA replication
External: Hormones or growth factors that stimulate the cell to continue through the
cycle (cell may move out of the cycle into G0 until other signals arrive)
Within the cell, the cycle is regulated by cyclically activated kinases.
Some kinases are activated towards end of G1 to send cell into S phase, other are
activated towards end of G2 sending cell into Mitosis. Activity of kinases is regulated by
proteins (cyclins) = CdKs
*activated kinase phosphorylates some of the proteins that cause condensation of the
chromosomes, nuclear envelop breakdown, and formation of the mitotic spindle.
• MPF=mitosis phase promoting factor=the CdK that sends cell into mitosis.
What is Contact Inhibition?
Cell growth stops when it comes in contact with other cells (tells them to go into G0). A chemical signal that involves cellcell
communication. Regulation of the cell cycle.
What roles do Growth Factors play? Give some examples of GFs.
Growth factors (FGF, EGF, Erythropoietin) signal cell to continue by stimulating it to produce CdKs. Growth factor binds to
receptor, could be sending message to nucleus to express certain
gene/could be coding for a stimulating protein
Erythropoietin signals growth/division of blood cells.
What are cyclins, CdKs, p53, p21, the Retinoblastoma protein, and how are they involved in the
regulation of the Cell Cycle?
Cyclins: proteins that stimulate kinases.
CdKs: cyclin dependent kinases – signal cell to continue through cycle.
p53: gene regulatory protein – increases when there is DNA damage. This stimulates the
transcription of p21.
p21: CdK inhibitor protein – binds to Sphase cyclin CdK complexes, blocking their action and
stopping DNA replication, then possibly leading down the path of DNA repair. Retinoblastoma protein: found in the nucleus of cells. It prevents certain proteins from stimulating transcription.
When in a quiescent state without a protein binded to the receptor, retino is wrapped around another protein (that would bind to
DNA and promote transcription of a gene, likely one that would tell the cell to continue through cycle) – preventing it form doing
When phosphorylated (by a CdK which was activated by a growth factor) and changes its shape, it releases the protein needed
for transcription and then it will transcribe the gene that can lead the cell through the cycle.
*In cancers, retino is phosphorylated and can’t do its job. Too many transcription proteins are available and cell goes through too
much growth and division.
In what part of the cell cycle would you observe chromatin and when would you observe
chromosomes? How are they related to each other?
Chromatin: found in Interphase. Unpaired fibers of DNA.
Chromosomes: Found in prophase, metaphase. Paired, condensed, ribbonlike.
Chromosomes are made up of chromatin (which become chromatid when they pair).
What are centromeres, unduplicated chromosomes, duplicated chromosomes, chromatids?
Centromeres: Center where sister chromatids are connected.
Unduplicated chromosomes: Essentially chromatid
Duplicated chromosomes: Look like a butterfly. Has one centromere. Has two chromatid with
the same DNA sequence.
Chromatids: Up/down paired strand of DNA sequence in duplicated chromosomes. When would you be able to see duplicated chromosomes and when during Mitosis would you be
able to see unduplicated chromosomes?
Duplicated: Prophase and metaphase
Unduplicated: Anaphase once the chromatids are split and become their own chromosomes.
What are the phases of Mitosis, what happens in each and how would you recognize a cell in that
Prophase: Whole nuclear structure breaks down and the spindle apparatus begins to form. Spindle fibers attach to the
centromeres. (Nucleolus disappears, chromatids condense into chromosomes, microtubules disassemble)
Metaphase: All the chromosomes are lined up in the center (metaphase plate). Chromosomes attach to spindle fibers and then
get pulled from both ends, but the pulling is equal so they kind of end up in the middle.
*Centromere divides between metaphase and anaphase.
Anaphase: Each chromatid is split and has its own centromere (so is a chromosome). Then they move to each pole. Cytokinesis
(division of cytoplasmic material) begins.
Telophase: Indentation forms in the cell (cleavage furrow) as it goes into telophase. Cytokinesis continues and finishes after
telophase. Nucleolus and nuclear envelope starts forming. Cells organize and separate more. What is the spindle apparatus, what is it made of, and what gives rise to it?
It is made of spindle fibers (microtubules). Centrioles move to opposite poles of the cell and fibers pull apart and pull on
How are chromatids related to each other and how are homologous chromosomes related to each
Homologous chromosomes: two chromosomes in the pair. They have genetic information for the same trait. (Ex; both
chromosomes #2 refer to eye color).
Chromatids: The two chromatids in a duplicated chromosome are identical (genes).
How can a cell go through mitosis and end up with the same number of chromosomes as it
Because the duplicated information is given to the daughter cells, so the parent cell keeps the original half (23 pairs – 46
What is cytokinesis and when does that happen?
The division of the cytoplasmic material. Happens during anaphase and ends at end of telophase.
Where does meiosis take place and why is this process important?
It takes place in the gonads (ovaries and testes). It results in the generation of 4 cells that have only one copy of each
chromosome (haploid) and therefore half the genetic material (egg and sperm cells).
What are the overall results of this process?
Each parents contrib