3A2 Growth and Development of Organisms

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 2 main phases of the cell cycle?

Answer 2

1. Interphase
2. Mitotic (M) Phase

Interphase includes G1, S, and G2, which focus on cell growth, copying DNA, and preparing for mitosis. The mitotic (M) phase is where the cell divides and goes through mitosis and cytokinesis.

Question 3

Define:

Mitosis

Answer 3

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 4

List the steps of mitosis in order.

Answer 4

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 5

Define:

Prometaphase

Answer 5

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 6

What happens during the G1 phase?

Answer 6

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 7

What happens in the Anaphase step of mitosis?

Answer 7

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 8

What happens during the S phase of the cell cycle?

Answer 8

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 9

Which phase directly follows the G2 phase?

Answer 9

M phase

(Mitosis)

During this phase, the cell divides, ensuring that each daughter cell receives an identical set of chromosomes.

Question 10

Describe what happens in the Metaphase stage of mitosis.

Answer 10

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 11

True or False:

Mitosis results in genetic variation between the daughter cells.

Answer 11

False

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

Question 12

Fill in the blank:

The G2 phase ensures that ______ is intact before mitosis.

Answer 12

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 13

True or False:

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

Answer 13

True

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

Question 14

Fill in the blank:

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

Answer 14

resting

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

Question 15

What happens in the prophase phase of mitosis?

Answer 15

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 16

What is produced during the G2 phase?

Answer 16

Proteins and organelles for cell division.

The G2 phase produces structures like microtubules needed for mitosis.

Question 17

What happens if errors are found during G2?

Answer 17

The cell repairs the DNA or halts division.

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

Question 18

Fill in the blank:

After telophase, the cell undergoes ________ to complete division.

Answer 18

cytokinesis

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

Question 19

True or False:

The nuclear envelope is fully reformed during anaphase.

Answer 19

False

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

Question 20

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

Answer 20

Telophase

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

Question 21

What is the role of spindle fibers during mitosis?

Answer 21

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 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 are the phases of Meiosis I?

Answer 23

1. Prophase I
2. Metaphase I
3. Anaphase I
4. Telophase I

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 24

True or False:

The purpose of meiosis is to produce gametes with half the chromosome number for sexual reproduction.

Answer 24

True

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

Question 25

What **type of cells** are produced by meiosis?

Answer 25

Gametes | (sperm and egg cells) ## Footnote The process creates haploid cells, each containing half the chromosome number of the original diploid cell.

Question 26

How many **divisions** occur in meiosis?

Answer 26

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

Question 27

What **two main factors** affect plant and animal growth?

Answer 27

1. Environmental factors 2. Genetic factors. ## Footnote *Genetic factors* determine inherited traits like height or leaf shape, while *environmental factors* (sunlight, water, nutrients) influence development and survival.

Question 28

# True or False: Only genetic factors **determine** how tall a tree grows.

Answer 28

False ## Footnote While genetics set the growth potential, *environmental factors* like soil quality, water, and sunlight impact actual growth.

Question 29

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

Answer 29

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

Question 30

What is **anaphase I** in meiosis?

Answer 30

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

Question 31

What is **telophase I** in meiosis?

Answer 31

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 32

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

Answer 32

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

Question 33

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

Answer 33

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 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

What is a **haploid** cell?

Answer 39

A cell with **half** the number of chromosomes. ## Footnote Haploid cells (like gametes) are produced during meiosis and contain *one set* of chromosomes.

Question 40

What is a **diploid** cell?

Answer 40

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 41

# Define: Cytokinesis

Answer 41

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 42

What marks the **end** of cytokinesis?

Answer 42

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

Question 43

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

Answer 43

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 44

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

Answer 44

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

Question 45

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

Answer 45

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

Question 46

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

Answer 46

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 47

What is a **multinucleated** cell?

Answer 47

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 48

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

Answer 48

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

Question 49

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

Answer 49

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 50

What is **binary fission**?

Answer 50

**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 51

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

Answer 51

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 52

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

Answer 52

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

Question 53

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

Answer 53

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

Question 54

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

Answer 54

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

Question 55

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

Answer 55

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

Question 56

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

Answer 56

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

Question 57

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

Answer 57

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

Question 58

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

Answer 58

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

Question 59

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

Answer 59

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

Question 60

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

Answer 60

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 61

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

Answer 61

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

Question 62

# True or False: All animals **reproduce** the same way.

Answer 62

False ## Footnote Animals reproduce through *sexual reproduction* (requiring two parents) or *asexual reproduction* (one parent, such as budding in hydras or fragmentation in starfish).

Question 63

Why do some animals perform **mating dances**?

Answer 63

To **attract a mate** for reproduction. ## Footnote Many species, like *birds* and *insects*, use visual signals, sounds, or scents to attract the best mates and increase their chances of successful reproduction.