Cell Division

Question 1

Telophase Events

Answer 1

Microtubule spindle fibers disintegrate

The nuclear membrane reforms around the daughter chromosomes

Chromosomes uncondensed and coil back to become no longer visible

During the entire process of mitosis, the cell undergoes cytokinesis and ends in telophase

Question 2

Prokaryotic and Eukaryotic Cells Division

Answer 2

Prokaryotic divides through binary fission
Eukaryotic divides through mitosis

Question 3

Cytokinesis in Animal Cell

Answer 3

A contractile protein ring forms around the equator of the cell and pulls the plasma membrane inwards. This inward pull is called the cleavage furrow, and when the cleavage furrow reaches the center of the cell it is pinched apart to form two daughter cells

Question 4

Prophase I Events

Answer 4

Replicated chromosomes condense by supercoiling and becoming visible

Replicated homologous chromosomes pair up to form bivalent and undergo crossing over

Spindle fibers form and stretch out from each pole to the equator

The nuclear membrane starts to break down

Question 5

How do Chromosomes Move

Answer 5

Kinetochores and Microtubules

Kinetochores are protein complexes that form on the centromere during cell division, and provide an attachment point for spindle fibers with the centromere region

Microtubules are hollow cylinders that can rapidly assemble and disassemble at the centrosome

Microtubules and Kinetochores work together by lengthening and shortening the microtubules to move chromosomes during cell division

Question 6

Meiosis

Answer 6

Reduction division in which the chromosome number is halved from diploid o haploid, resulting in genetically different cells

Question 7

Benign VS Malignant

Answer 7

Slow pace
Rapid and uncontrolled pace

Do not spread from site of origin
Detach and spread throughout the body

Unlikely to cause harm
Can cause harm and made of the same type of cell as the primary tumor

Not life-threatening
Life-threatening, known as cancer

Question 8

Importance of Centromere

Answer 8

Essential for the proper segregation of chromosomes during cell division

Question 9

Down Syndrome and Non-disjunction

Answer 9

Non-disjunction is when chromosomes fail to separate during gamete formation

Can happen in Anaphase I or II

In Anaphase I, the chromosomes pair fail to separate properly which results in the formation of 4 abnormal cells

In Anaphase II, the sister chromatids fail to separate properly which results in the formation of 2 abnormal cells

Question 10

Cell Growth during Interphase

Answer 10

DNA Replication: DNA is doubled through replication

Cytoplasmic Growth: Volume of the cytoplasm increases

Organelle Duplication: Mitochondria and chloroplast divide, mb-bound bud off from existing ones, and non-mb bound are assembled from the beginning

Protein Synthesis Cell synthesizes more proteins for more cellular processes

Question 11

Haploid and Diploid

Answer 11

Haploid: Contains one set of chromosomes and formed by meiosis

Diploid: Contains two sets of chromosomes and formed by mitosis

Question 12

Mitosis VS Meiosis

Answer 12

Takes place in body cells
Takes place in germ cells

Produces body cells
Produces gametes

Has 1 division
Has 2 divisions

2 identical diploid daughter cells are formed
4 different haploid daughter cells are formed

No crossing over
Crossing over

No variation
Variation

Question 13

Metaphase Events

Answer 13

Nuclear membrane disappears completely

Microtubules grow and attach to centromere’s kinetochores, and move them to align both sister chromatids towards the equator of the cell

Each sister chromatid faces a pole, and the spindle fibers are fully developed

Question 14

Prophase Events

Answer 14

Chromatin condense into chromosomes by supercoiling and becoming visible

The nuclear membrane starts disappearing

Centrosomes move to opposite poles of the cell and the microtubules start to form

Kinetochores start to appear on centromeres

Question 15

Cyclins

Answer 15

Proteins that control the progression of cells through the cycle, and act as checkpoints between two stages to ensure every task is performed

Cyclins bind to enzymes named CDK’s (cyclin dependent kinases) which phosphorylate specific proteins therefore making them become active and carry out tasks to continue the cell cycle. After the event occurred, the cyclin is degraded and the CDK is inactive

Question 16

Interphase Stages

Answer 16

G1: Where the cell grows and duplicates organelles and synthesizes proteins

S: Where DNA is replicated

G2: Where the cell continues to grow and make proteins needed for metabolic reactions in mitosis

Question 17

Anaphase I Events

Answer 17

Homologous chromosomes pairs are pulled to opposite poles thus halving the chromosome number

Centromeres do not split

Question 18

Purpose of Control of Cell Division

Answer 18

Ensures that each daughter cell receives an exact copy of their parent’s DNA

Maintains proper cell numbers by preventing uncontrolled division

Allows for cell differentiation to create various cell types

Allows for organism growth, tissue repair, and wound healing

Question 19

Metaphase I Events

Answer 19

The nuclear membrane is fully broken down

The paired up homologous chromosomes line up at the equator randomly and independently of each other

The spindle microtubules attach to the centromeres of the homologous chromosomes

Question 20

Interphase Processes

Answer 20

DNA Replication

Organelle Duplication

Cell Growth

Transcription and Translation

Protein Synthesis

Question 21

Mitotic Index

Answer 21

A measure of how fast cells are dividing

Formula is:

Cells in mitosis / total number of cells

Question 22

Budding Unequal Cytokinesis

Answer 22

A small bud sticks out from the parent yeast cell

The cytoplasm and organelles are unequally distributed, with the bud receiving a smaller portion compared to the parent cell

Over time, the bud grows and separates from the parent cell and becomes a new independent yeast cell

Question 23

Anaphase Events

Answer 23

Kinetochores use spindle fibers to split the centromere of each sister chromatid, thus pulling them to opposite poles

Each sister chromatid becomes a chromosome

Question 24

The 4 Phases of Mitosis

Answer 24

Prophase

Metaphase

Anaphase

Telophase

Question 25

Oogenesis Unequal Cytokinesis

Answer 25

Oogonia grows into primary oocyte

Primary oocyte undergoes Meiosis I which results in unequal cytokinesis

A large secondary oocyte forms which contains most of the cytoplasm which will become the mature egg, but the other daughter cell (polar body) has very little cytoplasm and eventually degenerates

Question 26

Condensation of Chromosomes

Answer 26

Nucleosomes wrap in a helical fashion to form a thick supercoil that stack over each other forming a single thick fiber named chromatin

Chromatin coils even further to form chromosomes which carries genetic information in the form of genes

Question 27

Homologous Chromosomes

Answer 27

Pairs of non-identical chromosomes in a diploid cell that are inherited from parents. They have same length, gene sequence, centromere positions, and same gene locus. They only differ from each other by alleles

Question 28

Cytokinesis in Plant Cell

Answer 28

Vesicles that come from the Golgi move to the center of the cell, and fuse together to form a cell plate. The cell plate continues to develop until it joins with the cell’s plasma membrane which completes the division of the cytoplasm, then both daughters secrete cellulose to form their new cell walls.

Question 29

Independent Assortment

Answer 29

In Metaphase I, bivalents line up randomly and independently of each other on the equator

Since they line up in any orientation on the equator, they segregate randomly

The possible combination of gametes depends on the number of homologous pairs and is calculated using 2^n,where n is the haploid number of chromosomes

Question 30

Meiosis I VS Meiosis II

Answer 30

Synapsis and crossing over occurs in Prophase I
Synapsis and crossing over doesn’t occur in Prophase II

Homologous pairs of chromosomes line up in the equator
Sister chromatids line up in the equator

Homologous pairs of chromosomes separate and move to opposite poles of the cell
Sister chromatids separate and move to opposite poles of the cell

2 haploid cells are formed
4 haploid cells are formed

Question 31

Characteristics of Cancer Cells

Answer 31

Do not differentiate

Have abnormal nuclei

Form tumor

Undergo metastasis

Question 32

Telophase I Events

Answer 32

Spindle microtubules disintegrate, and each chromosome from the homologous pair is found at opposite poles

A nuclear membrane starts reforming around each daughter nucleus

The membrane divides through Cytokinesis I

Chromosomes uncondensed and uncoil

Question 33

Crossing Over and Process

Answer 33

Exchange of alleles between non-sister chromatids of homologous chromosomes

In Prophase I, homologous chromosomes undergo synapsis thus forming a bivalent

A cut called SSB (Single Stranded Break) is made at the same part of DNA of each of the non-sister chromatids

Each non-sister chromatid re-joins with its homologous partner where they can then exchange genetic material through the chiasmata.

The chromatids formed after crossing over are called recombinant chromatids