Chapter 5: The Mitotic Cell Cycle

Question 1

What is the structure of a chromosome?

Answer 1

A chromosome consists of DNA wound around histone proteins, forming a compact structure.

Each chromosome is made of two identical sister chromatids joined at the centromere.

Telomeres are protective caps at the ends of chromosomes.

Question 2

What are histone proteins?

Answer 2

Histone proteins are proteins that help package and organize DNA into a compact structure in chromosomes.

Question 3

What are sister chromatids?

Answer 3

Sister chromatids are identical copies of a chromosome connected by a centromere.

Question 4

What is a centromere?

Answer 4

The centromere is the region of a chromosome where sister chromatids are joined and where the spindle fibers attach during mitosis.

Question 5

What are telomeres?

Answer 5

Telomeres are repetitive nucleotide sequences at the ends of chromosomes that protect them from degradation.

Each time a cell divides, telomeres shorten. When they become too short, the cell can no longer divide, leading to cellular aging and eventual cell death.

Question 6

What is the importance of mitosis?

Answer 6

Mitosis is crucial for the production of genetically identical daughter cells for growth, repair of tissues, replacement of damaged cells, and asexual reproduction.

Question 7

Outline the mitotic cell cycle.

Answer 7

The mitotic cell cycle includes:

Interphase (G1 phase: growth, S phase: DNA replication, G2 phase: growth)

Mitosis (prophase, metaphase, anaphase, telophase)

Followed by cytokinesis.

Question 8

What is the role of telomeres in DNA replication?

Answer 8

Telomeres prevent the loss of genes from chromosome ends during DNA replication by ensuring complete replication.

Question 9

What is the role of stem cells in tissue repair?

Answer 9

Stem cells contribute to cell replacement and tissue repair through mitosis, generating new cells to replace damaged ones.

Question 10

How can uncontrolled cell division lead to tumor formation?

Answer 10

Uncontrolled cell division can result in tumor formation when regulatory mechanisms fail, leading to excessive cell proliferation.

Question 11

Describe the behavior of chromosomes during mitosis.

Answer 11

During mitosis, chromosomes condense (Prophase) and align at the cell equator (Metaphase), separate into sister chromatids, and move to opposite poles (Anaphase) before the cell divides.

Question 12

What happens to the nuclear envelope during mitosis?

Answer 12

The nuclear envelope breaks down during prophase and re-forms during telophase as the daughter nuclei are created.

Question 13

What is the function of the spindle during mitosis?

Answer 13

The spindle fibers attach to the centromeres of chromosomes and help separate sister chromatids during mitosis.

Question 14

Explain the main stages of mitosis.

Answer 14

Prophase: Chromatin condenses into visible chromosomes, the nuclear envelope begins to break down, and the mitotic spindle forms.

Metaphase: Chromosomes align at the cell equator, with spindle fibers attaching to the centromeres.

Anaphase: Sister chromatids are pulled apart toward opposite poles of the cell as the spindle fibers shorten.

Telophase: Chromatids reach the poles, the nuclear envelope re-forms around each set of chromosomes, and the chromosomes begin to de-condense.

Question 15

What are centrioles?

Answer 15

Centrioles are cylindrical structures composed of microtubules, usually found in pairs. They play a crucial role in organizing the mitotic spindle and are involved in cell division, specifically during the formation of the spindle apparatus.

Question 16

What is a centrosome?

Answer 16

The centrosome is an organelle that serves as the main microtubule organizing center in animal cells. It contains a pair of centrioles and is essential for the formation of the mitotic spindle during cell division.

Question 17

Describe what happens during the Interphase

Answer 17

Divided into three phases:

G1 Phase (Gap 1): Cell grows and synthesizes proteins, increasing its size and preparing for DNA replication.

S Phase (Synthesis): DNA replication occurs, resulting in two sister chromatids for each chromosome.

G2 Phase (Gap 2): Further growth occurs, and the cell prepares for mitosis, checking for DNA damage and ensuring all DNA has been replicated.

Question 18

Cytokinesis

Answer 18

Cytokinesis is the final stage of cell division, where the cytoplasm divides.

In animal cells, a cleavage furrow forms, pinching the cell in two.

In plant cells, a cell plate forms along the center, leading to the formation of a new cell wall.

Question 19

What are Stem Cells

Answer 19

Stem cells are undifferentiated cells that can divide and differentiate into various cell types, enabling tissue repair and regeneration through mitosis.

Question 20

Stem Cell Potency ( Ability to Differentiate into specialized cells)

Answer 20

Totipotent Stem Cells: Can form all cell types, including embryonic and extra-embryonic tissues; present in early embryonic development.

Pluripotent Stem Cells: Can form nearly all cell types but not extra-embryonic tissues; derived from the inner cell mass of the blastocyst.

Multipotent Stem Cells: Can form a limited range of cell types within a specific tissue; found in various tissues for repair and maintenance.