Cell Cycle Study Guide - KEY
Define the following terms.
1. Binary fission – asexual reproduction by bacteria (splitting in 2)
2. Cell Cycle – life cycle of a cell (interphase, mitosis, cytokinesis)
3. Nuclear Envelope – nuclear membrane
4. Centromere – holds sister chromatids together in a chromosome
5. Kinetochore – protein on the centromere that allows spindle fibers to attach to chromosomes
6. Centrosome (which contains centrioles in animals) – contains centrioles which make/anchor
spindle fibers
7. Cleavage furrow – indention made in the cell membrane during cytokinesis
8. Cell plate – Plants can’t have a cleavage furrow because of their cell wall. They instead
make a new cell wall between the 2 new cells. This developing cell wall is called a cell plate.
9. Somatic cell – diploid “body” cell
10. Sister chromatids – identical copies on left and right side of a chromosome – made during
interphase
11. Homologous chromosomes – chromosomes that are the same size, shape, and carry the same
genes. These are the “pairs” of chromosomes that we all have (1 from mom and 1 from dad)
12. Gametes – haploid sex cells
13. Zygote – 1 cell baby made by fertilization of sperm and egg
14. Autosomes – homologous chromosome pairs 1-22. They are the same for boys and girls
15. Sex chromosomes – 23rd homologous chromosome pair. XX = girls and XY = guys
16. Crossing over – swapping of DNA segments between homologous chromosomes (during
prophase I)
17. Karyotype – picture of homologous chromosome pairs ordered from largest to smallest
Questions
18. How are prokaryotic and eukaryotic DNA different (Hint: talk about the # and shape of the
chromosomes)?
Prokaryotes have a single, circular strand of DNA.
Eukaryotes have multiple linear chromosomes that occur in pairs
19. What is binary fission?
asexual reproduction by bacteria (splitting in 2)
20. Amoebas are classified as Protists which means they are eukaryotes (have nucleus and membrane
bound organelles) but they are unicellular. Like bacteria, they are unicellular and reproduce
asexually. Even so, they must reproduce by mitosis and not binary fission. Why? (Do not write
“because they are eukaryotes”. What is it about being eukaryotic that makes them us mitosis
instead of binary fission?)
They can’t do binary fission because they can’t just “split in 2” because of their nucleus and
multiple chromosomes. They must do mitosis which still results in 2 clone cells.
21. Draw a eukaryotic chromosome and label the following: DNA, gene, chromatid, centromere,
kinetochore.
The chromosome is 1 piece of DNA. There are multiple genes (segments of DNA) on each
chromosome that would be the same on the left and right side. The kinetochore would be a
protein located on the centromere.
22. How are chromatin and chromosomes different?
Chromatin is DNA that is loose because it is not wrapped around histone proteins (looks
like spaghetti). DNA is in this form in interphase where it can be used but not divided.
Chromosomes are the exact same genetic material, but it is wrapped tightly around histone
proteins. DNA is in this form during mitosis where it cannot be used but can be divided
easily.
23. Draw a diagram showing how much time a cell spends in each stage of the cell cycle (I phase =
Interphase, M phase = Mitosis, C phase = cytokinesis).
24. Describe what occurs in each of the 3 phases of interphase. (Gap/Growth 1, Synthesis, and
Gap/Growth 2). Note: Gap/Growth 0 (G0) is the name given to a cell if it IS NOT going to
divide. These cells stay in interphase forever.
G1: Growth of the cell after division
S: replication of DNA
G2: continued growth of the cell to prepare for cell division
25. We talked about 4 stages of mitosis. List those 4 stages in order and describe what occurs during
each of these stages.
Prophase
 Hint to remember: Pro- means before. This stage is everything that must happen BEFORE
the cell can divide
 3 major occurrences of prophase:
o Chromatin becomes more tightly coiled, forming chromosomes so it can be divided
evenly
o Centrosomes (with centrioles in animals) make spindle fibers made of microtubules
o The nucleus & cytoskeleton are broken down and used to make the spindle fibers.
The nucleolus also disappears.
Metaphase
 Motor proteins connected to the spindle fibers have lined up chromosomes in the equator of
cell. This is called the metaphase plate.
 The two kinetochores of the chromatids face opposite poles of the spindle.
 Hint to remember: Metaphase = middle
Anaphase
 Spindle fibers pull the centromeres of each chromosome apart, separating the sister
chromatids.
 Once separated each chromatid is now considered a full fledged daughter chromosome.
 Chromosomes are then pulled away from each other to the poles of the cell.
 Hint to remember: “AAA” = Anaphase, Apart, Away
Telophase
 Telophase is the end of mitosis; therefore, it is the exact opposite of prophase.
 Cell elongation continues.
 Daughter nuclei appear at the two poles.
 Nuclear envelopes form around the chromosomes.
 Chromosomes begin to uncoil, into chromatin.
 Nucleolus reappear.
 Mitotic spindle disappears.
 Add: Hint to remember – Telophase - Two
26. What is cytokinesis, and how is it different between plants and animals?
Division of the cytoplasm. Plants = cell plate and animals = cleavage furrow
27. During what stage(s) of the cell cycle is DNA in chromatin form (Interphase or Mitosis)? Why?
Interphase so it can be used
28. During what stage(s) of the cell cycle is DNA in chromosome form (Interphase or Mitosis)?
Why?
Mitosis so it can be divided
29. During what phase of mitosis does the nuclear envelope disappear and when does it reappear?
Disappears in prophase so the DNA can be taken out of the nucleus and reappears in
telophase after the cell is done dividing
30. Which phase of mitosis is essentially the opposite of prophase in terms of nuclear changes? Why?
Telophase. Prophase begins cell division and telophase ends it.
31. Very important to know. During S phase of interphase you duplicate your DNA so you have
doubled the amount DNA. Even so, the number of chromosomes remains the same. Explain.
(Hint: use the terms centromere and sister chromatid)
You count the number of chromosomes by the number of centromeres. When you duplicate DNA,
you still have the same number of centromeres. You now just have 2 copies of the same DNA.
32. Very important to know. During anaphase of mitosis, you double the number of chromosomes
because you separate the sister chromatids into daughter chromosomes. How do you count the
number of chromosomes in a cell? Count the number of centromeres
Use the following diagram to answer questions 33-38
1
2
3
4
33. Write the name of each of the phases above.
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
34. During what stage do the spindle fibers eventually connect to the chromosomes? At the end of
prophase/start of metphase
35. What stage shows the nuclear envelope being reformed? telophase
36. Which stage shows the chromosome number doubling? Anaphase (because the sister
chromatids are separated there are now double the centromeres)
37. Which stage shows chromatin condensing to chromosomes? Prophase (preparing to divide)
38. Which stage shows centrosomes making spindle fibers? Prophase (to prepare to divide)
39. What is cancer? Uncontrolled cell division
40. What is metastasis? Cancer spreading through the blood
41. What is the difference between Carcinomas, Sarcomas, & Lymphomas?
 Carcinomas – cancer originating in the external or internal coverings of the body.
(skin, intestine)
 Sarcomas – cancer arising in tissues that support the body. (bone & muscle)
 Leukemias & Lymphomas – cancer arising from blood forming tissues. (bone
marrow, spleen, & lymph nodes)
42. What is the difference between a Benign & Malignant tumor?
Benign means it is not moving through metastasis. Malignant means the cancer is spreading
to other parts of the body through blood.
43. What are cells that are not a sperm or egg called? What are chromosomes not involved in
determining sex of an organism called?
Somatic cells; autosomes
44. We talked about the 4 stages of Meiosis 1. List those 4 stages in order and describe what happens
in each phase.
 Prophase I – duplicated homologous chromosomes fuse at the centromere in synapsis.
o Each of these pairs (4 chromatids) form a tetrad.
o Crossing over occurs between homologous non-sister chromatids.
 Metaphase I – tetrads (not individual chromosomes) line up in the center of the cell (called
the metaphase plate).
 Anaphase I – homologous pairs of chromosomes separate, but the sister chromatids stay
together.
 After Telophase I, there are two haploid cells, but each chromosome has two sister
chromatids.
45. What is synapsis and during what phase of meiosis does this occur?
Pairing of homologous chromosomes – prophase I
46. What is a tetrad and during what stage of meiosis does this occur?
The combined homologous chromosomes (tetrad because 4 sister chromatids) after synapsis
47. What type of cells does mitosis produce? What type of cells does meiosis produce?
Somatic cells; gametes
48. Complete the following table to compare mitosis and meiosis (very important to know this
information).
Mitosis
Meiosis
Number of choromosomal duplications
1
1
Number of cell divisions
1
2
Number of daughter cells produced
2
4
Number of chromosomes in daughter cells
46
23
Genetic relationship of daughter cells to
identical
Different (haploid)
parent cell (identical or different)
Functions performed in human body
Grow, repair, replace
Sex cells
49. If an intestinal cell in a grasshopper contains 24 chromosomes, a grasshopper sperm cell contains
how many chromosomes? 12 chromosomes (haploid = half)
50. If a frog gamete has 10 chromosomes, how many chromosomes are in its somatic cells?
20 (diploid = couble)
51. Why is it important that EVERY SEXUALLY REPRODUCING ORGANISM (humans, plants,
everything) be capable of alternating between a haploid and diploid stage in their life cycles. (For
humans, we are diploid and our reproductive cells are haploid).
So that we can get ½ DNA from mom and ½ from dad to make 1 whole baby