M4: Growth and Division of the Cell

Question 1

The cell cycle can be divided into a _ phase and a _ phase.

Answer 1

The cell cycle can be divided into a growth phase and a division phase.

Question 2

The part of the cycle without division was named “_.”

Answer 2

The part of the cycle without division was named “interphase.”

Question 3

Three phases can be detected during interphase.

Answer 3

G₁, S, and G₂

Question 4

The cell is recovering from division.

It conducts most of its normal metabolism.

Nucleotides are synthesized to be used for DNA replication.

In general, _ is the longest part of the cell cycle.

After cell cycle arrest, a cell may stay in a state similar to G₁ for life (Go).

Answer 4

G₁

Question 5

Genes in the nucleus are replicated.

Thousands of genes are attached in a linear sequence forming a chromosome.

Most plants have between 5 and 30 chromosomes.

Histones complex with DNA and give it both protection and structure.

Answer 5

S

Question 6

A chromosome has a centromere and is capped by a telomere on each end.

After replication, the two duplicates remain attached at the centromere.

Collectively they are referred to as a chromosome.

Each duplicate is a chromatid; sister chromatids

Answer 6

S

Question 7

Many cells stay in G₁ after they stop dividing.

Some enter S and replicate one or more times before differentiating: endoreduplication

Gene amplification

Only some genes are replicated.

Usually those needed for the specialized metabolism of the mature cell.

Answer 7

S

Question 8

Cells prepare for division.

The α- and β-tubulins necessary for spindle microtubules are synthesized.

The cell produces proteins for processing chromosomes and breaking down the nuclear envelope.

G₁, S, and G₂ constitute interphase.

After G₂, division can occur.

Answer 8

G₂ phase

Question 9

Division of the nucleus is called _.

Answer 9

karyokinesis

Question 10

There are two types of division:
_ − Duplication division
_ − Reduction division

Answer 10

Mitosis − Duplication division
Meiosis − Reduction division

Question 11

Division of the cytoplasm is _.

Answer 11

cytokinesis

Question 12

_ occurs as the body grows and increases in cell number.

The copies of the genome created in S phase are separated from each other.

Sister chromatids are separated into daughter cells in four phases.

Each is packed into its own nucleus.

Answer 12

Mitosis

Question 13

Mitosis is divided into phases:

Answer 13

Prophase
Metaphase
Anaphase
Telophase

Question 14

Chromosomes condense by coiling.

The nucleolus becomes invisible.

The nuclear envelope breaks into vesicles.

The spindle is composed of microtubules coming from opposite poles.

Spindle fibers attach to the __—a protein layer on each chromatid.

Answer 14

Mitosis Prophase

kinetochore

Question 15

Microtubules push and pull the chromosomes toward the cell center to form the metaphase plate.

At the end of metaphase, an enzyme breaks down the connection between sister chromatids.

Answer 15

Mitosis Metaphase

Question 16

Spindle microtubules shorten and pull the twin chromatids toward opposite poles of the cell.

Answer 16

Mitosis Anaphase

Question 17

Mostly a reversal of prophase

As the chromatids reach each pole of the cell, complete nuclear envelopes form and surround each group of chromatids.

Chromosomes uncondense.

New nucleoli appear.

The spindle depolymerizes and disappears.

Answer 17

Mitosis Telophase

Question 18

Division Phase: Cytokinesis

No matter how the protoplast divides, each half typically contains:

Answer 18

Mitochondria
Plastids
Endoplasmic reticulum (ER)
Vacuoles

Question 19

Division Phase: Cytokinesis

During prophase, the preprophase band forms just inside the plasma membrane.

Identifies the plane of division.

Marks the region where the new cell wall will attach to the existing wall.

Answer 19

Division Phase: Cytokinesis
+

Question 20

The _ is a set of short microtubules that forms in the center of the cell.

Answer 20

phragmoplast

Question 21

Phragmoplast traps dictyosome vesicles.

The vesicles fuse into a large, flat, plate-like vesicle.

Within this structure two new primary walls and a middle lamella begin to form.

Answer 21

Division Phase: Cytokinesis

Question 22

The phragmoplast, vesicle, and walls are called the _ _.

These grow outward until they fuse with those of the mother cell.

Answer 22

cell plate

Question 23

Vacuole division is accomplished with a phragmosome.

A set of microtubules, actin filaments, and cytoplasm

Question 24

_ is referred to as reduction division.

In order to have a _ , haploid sex cells () must fuse together.

Meiosis produces _ 1N cells from _ 2N cell.

Meiosis occurs only in the production of _ cells.

Answer 24

Meiosis

diploid zygote; gametes

four; one

reproductive cells

Question 25

Meiosis involves two rounds of division:
_
_
The _ phase does not occur after the first division.

Answer 25

Meiosis I and meiosis II

S

Question 26

_ is very similar to prophase of mitosis.

Exceptions are some unique chromosomal interactions.

Prophase I is divided into five stages:

Answer 26

Meiosis Prophase I

Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis

Question 27

_—chromosomes begin to condense and become distinguishable but indistinct.

Answer 27

Leptotene

Question 28

_—synapsis of homologs

A structure, the synaptonemal complex, is present between the paired homologous chromosomes.

A synapsed pair of homologous chromosomes is called a _.

Answer 28

Zygotene

bivalent

Question 29

_
Chromosomes shorten and thicken.

Crossing-over occurs between maternal and paternal homologs (involves the synaptonemal complex).

If the genes on the paternal and maternal chromosomes are slightly different, the new chromosomes that result are slightly different from the originals

Answer 29

Pachytene

Question 30

The homologous chromosomes move away from each other, but are held together by the centromeres.

They are tangled together at points called _.

Answer 30

Diplotene

chiasmata

Question 31

The homologs continue to separate
.
Chiasmata move toward ends until they become untangled.

They are paired only at the centromeres

Answer 31

Diakinesis

Question 32

Spindle microtubules move the homologs to the center of the cell, forming a metaphase plate.

Answer 32

Meiosis Metaphase I

Question 33

The homologs separate, moving to opposite ends of the spindle.

Two new haploid nuclei have formed.

Answer 33

Meiosis Anaphase I

Question 34

_ —usually occurs partially.
The chromosomes begin to uncoil.

The nuclear envelope forms and nucleoli appear.

If the cells progress to interphase, the S phase does not occur—_.

Answer 34

Meiosis Telophase I

interkinesis

Question 35

Prophase II prepares the nucleus for division (if telophase I has occurred).

Centromeres divide at the end of metaphase II, separating the chromatids into two chromosomes.

Anaphase II pulls the separated chromosomes to each side of the cell.

In telophase II, new nuclei form.
Each nucleus is haploid.

Answer 35

Meiosis II

Question 36

Less Common Types of Division

In numerous tissues, karyokinesis occurs without cytokinesis.

Multinucleate cells are formed called _.

Cell division may occur without nuclear division.

This is most common in algae, fungi, and the nutritive tissues of seeds.

Answer 36

coenocytes

Question 37

Groups of organisms with unusual nuclear characteristics may represent lines of evolution that originated earlier than plants and animals.

In many algae and fungi, the nuclear envelope and nucleoli do not break down until late in mitosis, if at all.

Nuclei of dinoflagellates have no histones and chromosomes remain mostly condensed.

Answer 37

Cell Division in Algae: Nuclei

Question 38

In unicellular algae with no walls, cytokinesis occurs similarly to animals, but in those with walls, cell division is similar to plants.

In some green algae, cytokinesis occurs by use of a phycoplast.

Phycoplasts are associated with divisions where the nuclear envelope does not break down.

In red algae, cell division occurs by a phragmoplast, but the new wall grows inward from the pre-existing walls.

Answer 38

Cell Division in Algae: Cytokinesis

Question 39

Division by binary fission; mitosis and meiosis |do not occur.

Circular DNA replicates attached to the cell membrane.

The replicates are separated by membrane growth.

Cytokinesis occurs by a process of _.

The plasma membrane pulls inward and pinches in two.

Answer 39

Cell Division: Prokaryotes

infurrowing

Question 40

The circular DNA is replicated as in prokaryotes.

Division occurs either by infurrowing or by being pulled in two.

The replication of organelles and their DNA is episodic.

Replication appears to be continuous throughout interphase

Answer 40

Division: Chloroplasts and Mitochondria