3A2 Cell Reproduction and Division

Question 1

Define:

Cell cycle

Answer 1

A series of events that lead to cell division and replication.

It consists of several phases, ensuring that the cell grows, replicates its DNA, and divides properly.

Question 2

What are the 5 phases of the cell cycle?

Answer 2

1. G0 (Resting Phase)
2. G1 (Cell Growth)
3. S (DNA Replication)
4. G2 (Preparation Phase)
5. M (Cell Division/Mitosis)

Each phase of the cell cycle has a different function in the life of the cell.

Question 3

Fill in the blank:

The G0 phase is a ________ phase where cells are not actively dividing.

Answer 3

resting

Cells in this phase are in a dormant state and may not proceed through the cell cycle unless triggered by specific signals.

Question 4

What happens during the G1 phase?

Answer 4

The cell grows and prepares for DNA replication.

The cell increases in size and synthesizes proteins and organelles in preparation for DNA synthesis in the next phase, the S phase.

Question 5

What happens during the S phase of the cell cycle?

Answer 5

DNA replication

In this phase, the entire DNA content of the cell is duplicated, ensuring that each daughter cell will have a complete set of chromosomes.

Question 6

Fill in the blank:

The G2 phase ensures that ______ is intact before mitosis.

Answer 6

DNA

The G2 phase ensures DNA integrity by proofreading and repairing errors before cell division. Any errors in DNA would be copied when the cell divides, so this step is imperative.

Question 7

What happens if errors are found during G2?

Answer 7

The cell repairs the DNA or halts division.

The G2 checkpoint ensures that any DNA damage is fixed before mitosis begins.

Question 8

What is produced during the G2 phase?

Answer 8

Proteins and organelles for cell division.

The G2 phase produces structures like microtubules needed for mitosis.

Question 9

Which phase directly follows the G2 phase?

Answer 9

M phase

(Mitosis)

Question 10

Define:

Mitosis

Answer 10

The process of cell division that results in two identical daughter cells.

It ensures that each daughter cell has the same number and type of chromosomes as the original cell.

Question 11

List the steps of mitosis in order.

Answer 11

1. Prophase
2. Prometaphase
3. Metaphase
4. Anaphase
5. Telophase

Following telophase, the cells physically divide through cytokinesis. Some scientists consider cytokinesis as part of mitosis, while others consider it a separate process.

Question 12

What happens in the Prophase step of mitosis?

Answer 12

Chromosomes condense and the mitotic spindle is formed.

This first step prepares the chromosomes for separation by condensing them into very small X-shaped structures. The centrosomes of the cell move to opposite sides, initiating the formation of the mitotic spindle.

Question 13

Define

Prometaphase

Answer 13

The second stage of mitosis where the nuclear envelope breaks down and kinetochores are formed.

In this phase, the chromosomes attach to the mitotic spindles. The site where chromosomes attach to the spindle is known as the kinetochore.

Question 14

Describe what happens in the Metaphase stage of mitosis.

Answer 14

The chromosomes line up at the metaphase plate and fully attach to the mitotic spindles.

The metaphase plate is not a real structure, but refers to the region in the middle of the cell where the chromosomes line up.

Question 15

What happens in the Anaphase step of mitosis?

Answer 15

Sister chromatids separate and are pulled to opposite ends of the cell by the mitotic spindle.

The proteins that held together the chromatids break down, allowing for the separation and movement of the individual chromatids.

Question 16

True or False:

The nuclear envelope is fully reformed during anaphase.

Answer 16

False

Anaphase is when the sister chromatids are pulled apart. The nuclear envelope reforms during telophase.

Question 17

What phase involves chromosomes de-condensing and the nuclear envelope re-forming?

Answer 17

Telophase

This phase marks the near end of mitosis, where the cell prepares to divide into two.

Question 18

What is the role of spindle fibers during mitosis?

Answer 18

The attach to centromeres and pulls chromatids apart during separation.

These fibers are crucial for ensuring that each daughter cell receives an equal set of chromosomes.

Question 19

True or False:

Mitosis results in genetic variation between the daughter cells.

Answer 19

False

This process produces genetically identical daughter cells, ensuring that the genetic material is faithfully copied and distributed.

Question 20

Fill in the blank:

After telophase, the cell undergoes ________ to complete division.

Answer 20

cytokinesis

Cytokinesis physically separates the cytoplasm of the two daughter cells, finalizing the division process after mitosis.

Question 21

True or False:

During telophase, the chromosomes begin to de-condense, and a new nuclear envelope forms.

Answer 21

True

Near the end of mitosis, the nuclear envelope reforms around the chromosomes, and the chromatin begins to unwind.

Question 22

What is meiosis?

Answer 22

The process of cell division that produces four non-identical gametes.

This process reduces the chromosome number by half, ensuring genetic diversity in offspring.

Question 23

What type of cells are produced by meiosis?

Answer 23

Gametes

(sperm and egg cells)

The process creates haploid cells, each containing half the chromosome number of the original diploid cell.

Question 24

What is a haploid cell?

Answer 24

A cell with half the number of chromosomes.

Haploid cells (like gametes) are produced during meiosis and contain one set of chromosomes.

Question 25

What is a **diploid** cell?

Answer 25

A cell with **two** complete sets of chromosomes. ## Footnote *Somatic cells* are diploid, meaning they have two sets of chromosomes, one from each parent.

Question 26

# True or False: The **purpose** of meiosis is to produce gametes with half the chromosome number for sexual reproduction.

Answer 26

True ## Footnote This process ensures genetic variation and allows for fertilization to restore the diploid number of chromosomes.

Question 27

How many **divisions** occur in meiosis?

Answer 27

Two ## Footnote **Meiosis I** reduces the chromosome number, and **Meiosis II** divides the chromosomes into four unique gametes.

Question 28

What are the phases of **Meiosis I**?

Answer 28

1. Prophase I 2. Metaphase I 3. Anaphase I 4. Telophase I ## Footnote This first round of cell division is similar to mitosis, but difers in that the resulting daughter cells half have the chromosomes of the parent cell.

Question 29

What are the phases of **Meiosis II**?

Answer 29

1. Prophase II 2. Metaphase II 3. Anaphase II 4. Telophase II ## Footnote Following Telophase II, the daughter cells undergo cytokinesis to split into the final product, 4 haploid cells.

Question 30

# Fill in the blank: \_\_\_\_\_\_\_\_ \_\_\_\_\_ is the **exchange** of genetic material between homologous chromosomes.

Answer 30

Crossing over ## Footnote Crossing over occurs during prophase I of meiosis and increases genetic diversity.

Question 31

What is **anaphase I** in meiosis?

Answer 31

The homologous chromosomes are pulled **toward** opposite poles. ## Footnote In anaphase I, the chromosome pairs separate, reducing the chromosome number by half.

Question 32

What is **telophase I** in meiosis?

Answer 32

The chromosomes arrive at opposite poles, and the cell **starts** to divide. ## Footnote Telophase I concludes meiosis I, leading to the formation of *two* haploid cells.

Question 33

What **phase** separates the sister chromatids of each chromosome?

Answer 33

Meiosis II ## Footnote Meiosis II is similar to mitosis but with haploid cells as the starting point.

Question 34

What **happens** in prophase II of meiosis?

Answer 34

Chromosomes *condense*, and the nuclear membrane *dissolves*. ## Footnote **Prophase II** prepares the haploid cells for the separation of sister chromatids.

Question 35

# True or False: Chromosomes **align** at the cell's equator during metaphase II of meiosis.

Answer 35

True ## Footnote Similar to metaphase in *mitosis*, this step ensures chromosomes will be evenly split.

Question 36

# Fill in the blank: During **anaphase II** of meiosis, \_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_ are pulled to opposite poles of the cell.

Answer 36

sister chromatids ## Footnote Anaphase II ensures that each new cell will receive one chromatid from each chromosome.

Question 37

What is **synapsis** in meiosis?

Answer 37

The **pairing** of homologous chromosomes during prophase I. ## Footnote Synapsis is crucial for crossing over and the proper alignment of chromosomes for meiosis.

Question 38

What is the role of **spindle fibers** in meiosis?

Answer 38

They help **separate chromosomes** during cell division. ## Footnote These form during both meiosis I and meiosis II to guide chromosome movement.

Question 39

# Define: Cytokinesis

Answer 39

The process where the **cytoplasm of a parental cell divides** into two daughter cells. ## Footnote This process usually occurs after mitosis or meiosis, completing cell division and resulting in two distinct cells.

Question 40

What marks the **end** of cytokinesis?

Answer 40

The formation of **two separate daughter cells**. ## Footnote The two daughter cells have their *own* cytoplasm, organelles, and membrane.

Question 41

What **structure** forms in plant cells during cytokinesis?

Answer 41

The cell plate. ## Footnote In *plant cells*, the cell plate forms in the middle and eventually develops into the cell wall, separating the two daughter cells.

Question 42

# True or False: Cytokinesis occurs **before** mitosis.

Answer 42

False ## Footnote Cytokinesis occurs **after** mitosis or meiosis, finalizing the division of the cell into two daughter cells.

Question 43

# Fill in the blank: In animal cells, cytokinesis involves the **formation** of a \_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_.

Answer 43

cleavage furrow ## Footnote This pinches the cell membrane in two, eventually splitting the cell into two daughter cells.

Question 44

What **forms** during the process of cleavage furrow formation?

Answer 44

A **contractile ring** of actin filaments. ## Footnote This helps to tighten and pinch the membrane, leading to the division of the cell's cytoplasm.

Question 45

What happens if cytokinesis **does not occur properly**?

Answer 45

It can lead to **multinucleated cells** or **cell division errors**. ## Footnote This can result in cells with more than one nucleus or other cell division abnormalities.

Question 46

What is a **multinucleated** cell?

Answer 46

A cell with **more than one nucleus** due to incomplete cytokinesis. ## Footnote They can result from failed cytokinesis, where the division of the cytoplasm doesn’t occur correctly.

Question 47

# True or False: Cytokinesis is the **final** stage of cell division.

Answer 47

True ## Footnote Cytokinesis marks the final step of cell division, ensuring the formation of *two* daughter cells.

Question 48

# Fill in the blank: During cytokinesis, the \_\_\_\_\_\_ \_\_\_\_\_\_\_ moves **toward** the center of the dividing cell in plant cells.

Answer 48

cell plate ## Footnote The cell plate grows in the **center** of the plant cell and eventually fuses with the membrane to separate the daughter cells.

Question 49

What is **binary fission**?

Answer 49

**Asexual reproduction** where one cell divides into two identical cells. ## Footnote It is common in *prokaryotes* like bacteria and some single-celled eukaryotes, enabling rapid population growth.

Question 50

What is the main **advantage** of binary fission?

Answer 50

It allows for **rapid** reproduction. ## Footnote This process enables prokaryotes to quickly increase their population in favorable conditions.

Question 51

What is the **first** step in binary fission?

Answer 51

DNA replication ## Footnote Before a cell can divide, it must *replicate* its DNA so each daughter cell receives an identical copy.

Question 52

# True or False: Binary fission **requires** a partner organism.

Answer 52

False ## Footnote Binary fission is an *asexual* process, meaning it does not require a mate for reproduction.

Question 53

# Fill in the blank: Binary fission is most **commonly** observed in \_\_\_\_\_\_\_\_\_\_.

Answer 53

prokaryotes ## Footnote Bacteria and archaea use binary fission as their primary mode of reproduction.

Question 54

What happens to the **replicated DNA** during binary fission?

Answer 54

It **moves to the opposite sides** of the cell. ## Footnote This step ensures that each daughter cell inherits one copy of the DNA.

Question 55

What is the **dividing structure** in bacterial binary fission?

Answer 55

The septum ## Footnote The **septum** is a dividing wall formed during binary fission that separates the two daughter cells.

Question 56

# True or False: Binary fission is **faster** than mitosis.

Answer 56

True ## Footnote This is a simpler and quicker process compared to mitosis because it does not involve a complex nucleus.

Question 57

# Fill in the blank: Binary fission **produces** \_\_\_\_\_\_\_\_\_\_ copies of the parent cell.

Answer 57

identical ## Footnote The daughter cells have identical genetic material unless a mutation occurs during DNA replication.

Question 58

How does binary fission **benefit pathogenic bacteria**?

Answer 58

It allows them to **rapidly infect** a host. ## Footnote Bacteria like Salmonella or E. coli use binary fission to multiply quickly, increasing their ability to spread and cause disease.

Question 59

Why is binary fission important in **microbiology**?

Answer 59

It explains how **microorganisms reproduce** and grow. ## Footnote Understanding binary fission helps scientists **study** bacterial behavior, antibiotic resistance, and disease transmission.