Chapter 10: Cellular Division: Mitosis

Question 1

Describe the structure of prokaryotic and eukaryotic genomes

Answer 1

Prokaryotic genome: commonly consists of a single DNA molecule

Eukaryotic genome: commonly consist of multiple DNA molecules

Question 2

Dyad chromosomes

Answer 2

consist of two sister chromatids

Question 3

Sister Chromatids

Answer 3

Identical pairs of chromatids

Question 4

Describe the eukaryotic cell cycle

Answer 4

G1 (gap phase 1) Primary growth phase, longest phase

G1 checkpoint – the primary point at which it
must choose whether or not to divide,

S (synthesis) Replication of DNA; Centrosome is duplicated

G2 (gap phase 2) Organelles replicate, microtubules organize

G2 checkpoint – checks for DNA
damage, DNA replication completeness

M (mitosis) Subdivided into 5 phases

C (cytokinesis) Separation of 2 new cells

IF A CELL EXITS THE CELL CYCLE, IT IS CONSIDERED TO BE IN
G0 (G ZERO)

Question 5

Discuss the progression and phases of mitosis

Answer 5

Prophase - Chromosomes condense, Start seeing centrosomes, Micro Tubule Organization Center (MTOC)

Prometaphase - Explosion of nuclear envelope, you will see nuclear envelope fragments, microtubules start to connect to kinetochore

Metaphase - Meet in the middle, Aligned

Anaphase - Chromatids separate

Telophase - Daughter nuclei starts to form, Cell elongates, Cleavage furrow appears

Question 6

Distinguish the role of checkpoints

Answer 6

Cell cycle checkpoints are control mechanisms in the eukaryotic cell cycle
which ensure its proper progression.

Each checkpoint serves as a potential
termination point along the cell cycle

Question 7

Describe how the cell cycle is controlled by positive

mechanisms

Answer 7

Two groups of proteins, called cyclins and cyclin-dependent
kinases (Cdks), are responsible for the progress of the cell through the
various checkpoints.

Question 8

Describe how the cell cycle is controlled by negative

mechanisms

Answer 8

The role of normal p53 is to monitor DNA and the supply of
oxygen (hypoxia is a condition of reduced oxygen supply). If damage is
detected, p53 triggers repair mechanisms. If repairs are unsuccessful, p53
signals apoptosis.

Question 9

Explain how the three internal control checkpoints occur at the end of G1, at the
G2/M transition, and during metaphase

Answer 9

i. G1/S checkpoint
1. Cell “decides” to divide •Primarily influenced by internal and
external signals; Monitors size cell has achieved –Evaluates
condition of DNA
ii. G2/M checkpoint
1. Cell makes a commitment to mitosis
2. Assesses success of DNA replication
3. Monitors if DNA replication is incomplete –Monitors damaged
DNA
iii. Late metaphase (spindle) checkpoint
1. Cell ensures that all chromosomes are attached to the spindle
2. Monitors successful formation of spindle fiber system and
attachment to kinetochores

Question 10

How does Binary Fission work?

Answer 10

Prior to cell division, the bacterial DNA molecule replicates. The
replication of the double-stranded, Circular DNA mole- cule that
constitutes the genome of a bacterium begins at a specific site,
called the origin of replication
2. The replication enzymes move out in both directions from that site
and make copies of each strand in the DNA duplex. The enzymes
continue until they meet at another specific site, the terminus of
replication
3. As the DNA is replicated, the cell elongates, and the DNA is
partitioned in the cell such that the origins are at the ¼and ¾
positions in the cell and the termini are oriented toward the
middle of the cell.
4. Septation then begins, in which new membrane and cell wall
material begin to grow and form a septum at approximately the
midpoint of the cell. A protein molecule called FtsZ (orange dots)
facilitates this process.
5. When the septum is complete, the cell pinches in two, and two daughter cells are formed