Cell Division

Front 1

Cell cycle

Back 1

A series of events from the time a cell forms until its cytoplasm divides.

Front 2

A typical cell spends most of its life in _____

Back 2

interphase

Front 3

interphase

Back 3

In a eukaryotic cell cycle, the interval between mitotic divisions when a cell enlarges, roughly doubles the number of its cytoplasmic components, and replicates its DNA.

Front 4

Cell cycle (image)

Back 4

Front 5

Stages of interphase

Back 5

G1, S, G2

Front 6

G1

Back 6

the first interval (or gap) of cell growth, before DNA replication

Front 7

S

Back 7

the time of synthesis (DNA replication)

Front 8

G2

Back 8

the second interval (or gap), when the cell prepares to divide

Front 9

Actually, most cells going about their metabolic business are in ___.

Back 9

G1

Front 10

During ____, they make the proteins that will drive cell division

Back 10

G2

Front 11

Mitosis

Back 11

Nuclear division mechanism that maintains the chromosome number. Basis of body growth and tissue repair in multicelled eukaryotes; also asexual reproduction in some plants, animals, fungi, and protists.

Front 12

In multicelled species, ______ and _______ increase cell number during development, and replace damaged or dead cells later in life

Back 12

mitosis; cytoplasmic division

Front 13

Asexual reproduction

Back 13

Reproductive mode by which offspring arise from a single parent only.

Front 14

______ ___________ have the same length, shape, and genes (hom– means alike). Typically, each member of a pair was inherited from one of two parents.

Back 14

Homologous chromosomes

Front 15

Homologous chromosomes

Back 15

Chromosomes with the same length, shape, and set of genes.

Front 16

Most differentiated cells in a human body are in ___, and some types never progress past that stage

Back 16

G1

Front 17

When a nucleus divides by _____, each new nucleus has the ____ chromosome number as the parent cell.

Back 17

mitosis; same

Front 18

Four main stages of mitosis

Back 18

Prophases; metaphase; anaphase; telophase

Front 19

Prophase

Back 19

Stage of mitosis during which chromosomes condense and become attached to a newly forming spindle.

Front 20

When a nucleus divides by mitosis, each new nucleus has the ____ chromosome number as the parent cell.

Back 20

same

Front 21

During __________, a cell's chromosomes are loosened to allow transcription and DNA replication

Back 21

interphase

Front 22

Stage of mitosis during which chromosomes condense and become attached to a newly forming spindle.

Back 22

Prophase

Front 23

A typical centrosome consists of two _______, which are barrel-shaped organelles that help microtubules assemble, surrounded by a region of dense ______.

Back 23

centrioles; cytoplasm

Front 24

The centrosome gets duplicated just before _____.

Back 24

prophase

Front 25

Spindle

Back 25

Dynamically assembled and disassembled network of microtubules that moves chromosomes during nuclear division.

Front 26

Plant cells have spindles and structures that organize them, but no ______.

Back 26

centrosomes

Front 27

Metaphase

Back 27

Stage of mitosis at which the cell's chromosomes are aligned midway between poles of the spindle.

Front 28

Anaphase

Back 28

Stage of mitosis during which sister chromatids separate and move to opposite spindle poles.

Front 29

Telophase

Back 29

Stage of mitosis during which chromosomes arrive at the spindle poles and decondense, and new nuclei form.

Front 30

______ begins when the two clusters of chromosomes reach the spindle poles.

Back 30

Telophase

Front 31

What is the sequence of events in mitosis?

Back 31

Each chromosome in a cell's nucleus was duplicated before mitosis begins, so each consists of two DNA molecules.

Mitosis proceeds in four stages: prophase, metaphase, anaphase, and telophase.

During these four stages, sister chromatids of the duplicated chromosomes are separated and packaged into two new nuclei. Each new nucleus contains the same number and types of chromosomes as the parent cell.

Front 32

In most eukaryotes, the cell cytoplasm divides between late ______ and the end of _____. The mechanism of division differs between plants and animals.

Back 32

anaphase; telophase

Front 33

A cell's cytoplasm usually divides after _____, so two cells form.

Back 33

mitosis

Front 34

Cytoplasmic division

Back 34

Cytokenisis

Front 35

The process of cytoplasmic division, which is called cytokinesis , differs among _____.

Back 35

Eukaryotes

Front 36

The spindle begins to disassemble during ______.

Back 36

telophase

Front 37

In a dividing animal cell, the indentation where cytoplasmic division will occur.

Back 37

Cleavage furrow

Front 38

Cyotplasmic division (image)

Back 38

Front 39

Cell plate

Back 39

After nuclear division in a plant cell, a disk-shaped structure that forms a cross-wall between the two new nuclei.

Front 40

When the cell ____ attaches to the membrane, it partitions the cytoplasm.

Back 40

plate

Front 41

Plant cell cytoplasmic division (image)

Back 41

Front 42

How do eukaryotic cells divide?

Back 42

After mitosis, the cytoplasm of the parent cell typically is partitioned into two descendant cells, each with its own nucleus.

In animal cells, a contractile ring pinches the cytoplasm in two. In plant cells, a cell plate that forms midway between the spindle poles partitions the cytoplasm when it reaches and connects to the parent cell wall.

Front 43

______ protect eukaryotic chromosomes from losing genetic information at their ends.

Back 43

Telomeres

Front 44

_____ telomeres are associated with aging.

Back 44

Shortening

Front 45

Telomeres

Back 45

Noncoding, repetitive DNA sequence at the end of chromosomes; protects the coding sequences from degradation.

Front 46

The chromosomes of a normal eukaryotic body cell _____ by about 100 bases with each replication

Back 46

shorten

Front 47

Why can cells only divide a certain number of times?

Back 47

When telomeres get too short, checkpoint gene products come into play to halt the cell cycle. The cell stops dividing, and it dies shortly thereafter.

Front 48

What types of cells retain the ability to divide indefinitely in adults?

Back 48

Stem cells

Front 49

Why are stem cells immortal?

Back 49

Stem cells are immortal because they continue to make telomerase, a molecule that consists of a non-coding RNA and a replication enzyme.

Front 50

What is the function of telomeres?

Back 50

Telomeres at the ends of chromosomes provide a buffer against loss of genetic information.

Telomeres shorten with every cell division in normal body cells. When they get too short, the cell stops dividing and dies.

Front 51

On rare occasions, controls over cell division are lost and a ____ forms.

Back 51

neoplasm

Front 52

Cancer develops as cells of a neoplasm become _____.

Back 52

malignant

Front 53

_____ is a nuclear division process that occurs only in cells set aside for sexual reproduction.

Back 53

Meoisis

Front 54

Meiosis reduces the chromosome number by sorting chromosomes into ___ new nuclei.

Back 54

4

Front 55

During ____, homologous chromosomes swap segments, then are randomly sorted into separate nuclei. Both processes lead to novel combinations of ___ among offspring.

Back 55

meoisis; alleles

Front 56

Gametes form by different mechanisms in males and females, but____ is part of both processes.

Back 56

meoisis

Front 57

In most plants, ____ occur between meiosis and gamete formation.

Back 57

spores

Front 58

Nuclear division process that halves the chromosome number. Basis of sexual reproduction.

Back 58

Meiosis

Front 59

Sexual reproduction mixes up _____ from two parents.

Back 59

alleles

Front 60

Meiosis, the basis of sexual reproduction, is a nuclear division mechanism that occurs in____ _______ ______ of eukaryotes.

Back 60

immature reproductive cells

Front 61

Except for a pairing of nonidentical sex chromosomes, _____ chromosomes carry the same set of genes

Back 61

homologous

Front 62

Different forms of a gene are called _____.

Back 62

Alleles

Front 63

The two chromosomes of a homologous pair are typically not identical. Why not?

Back 63

Mutations that inevitably occur in chromosomes change their DNA sequence. Over time, unique mutations accumulate in separate lines of descent, and some of those mutations occur in gene regions. Thus, any gene may differ a bit in sequence from the corresponding gene on the homologous chromosome.

Front 64

Alleles

Back 64

Forms of a gene with slightly different DNA sequences; may encode slightly different versions of the gene's product.

Front 65

Gamete

Back 65

Mature, haploid reproductive cell; e.g., an egg or a sperm.

Front 66

Sexual reproduction involves the fusion of _____reproductive cells—gametes —from two parents.

Back 66

haploid

Front 67

Immature reproductive cell that gives rise to haploid gametes when it divides.

Back 67

Germ cells

Front 68

Gametes have a single set of chromosomes, so they are ____

Back 68

haploid (n)

Front 69

Haploid

Back 69

Having one of each type of chromosome characteristic of the species.

Front 70

The diploid chromosome number is restored at ______ , when two haploid gametes (one egg and one sperm, for example) fuse to form a _____ , the first cell of a new individual.

Back 70

fertilization; zygote

Front 71

Fusion of two gametes to form a zygote

Back 71

Fertilization

Front 72

Zygote

Back 72

Diploid cell formed by fusion of two gametes; the first cell of a new individual.

Front 73

Meiosis ____ the chromosome number.

Back 73

halves

Front 74

During meiosis, chromosomes of a _____ nucleus become distributed into four ____ nuclei.

Back 74

diploid; haploid

Front 75

____and the ___ ___ of chromosomes into gametes result in new combinations of traits among offspring of sexual reproducers.

Back 75

Crossovers; random sorting

Front 76

Crossing over

Back 76

Process in which homologous chromosomes exchange corresponding segments during prophase I of meiosis.

Front 77

Two kinds of multicelled bodies form during the life cycle of a plant:

Back 77

sporophytes and gametophytes

Front 78

Sporophyte

Back 78

Diploid, spore-producing stage of a plant life cycle.

Front 79

Gametophyte

Back 79

A haploid, multicelled body in which gametes form during the life cycle of land plants and some algae.

Front 80

Animal gametes arise by meiosis of __ __ __

Back 80

diploid germ cells

Front 81

Sperm formation

Back 81

Front 82

Egg formation (image)

Back 82

Front 83

What is a chromosome?

Back 83

A structure that consists of DNA and associated proteins
Carries part or all of a cell’s genetic information

Front 84

Chromosome structure

Back 84

Front 85

Each duplicated chromosome has two DNA strands (sister chromatids) attached to one another at the ______

Back 85

centromere

Front 86

Division of a eukaryotic cell typically occurs in two steps:

Back 86

nuclear division followed by cytoplasmic division

Front 87

What are the three stages of the cell cycle?

Back 87

Interphase, mitosis, and cytoplasmic division

Front 88

Describe interphase

Back 88

Interphase consists of three stages, during which a cell increases in size, doubles the number of cytoplasmic components, and replicates its DNA
G1: Interval of cell growth and activity
S: Interval of DNA replication (synthesis)
G2: Interval when the cell prepares for division

Front 89

____ is a nuclear division mechanism that maintains the chromosome number.

Back 89

Mitosis

Front 90

What is the function of mitosis?

Back 90

In multicelled species, mitosis and cytoplasmic division increase cell number during development and replace damaged or dead cells later in life

Front 91

During ______, a cell’s chromosomes are loosened to allow transcription and DNA replication

Back 91

interphase

Front 92

Why do chromosome condense to prepare for nuclear division?

Back 92

Tight condensation keeps the chromosomes from getting tangled and breaking during nuclear division

Front 93

What happens in prophase?

Back 93

Chromosomes condense
Microtubules form a bipolar spindle
Nuclear envelope breaks up
Microtubules attach to the chromosomes

Front 94

What is a centrosome?

Back 94

A region near the nucleus that organizes spindle microtubules; usually includes two centrioles

Front 95

What is a spindle?

Back 95

A dynamic network of microtubules that forms during nuclear division
Grows into the cytoplasm from opposite poles of the cell and attaches to duplicated chromosomes
Microtubules from opposite poles attach to different sister chromatids and separate them

Front 96

What happens in metaphase?

Back 96

All duplicated chromosomes line up midway between the spindle poles

Front 97

What happens in anaphase?

Back 97

Microtubules separate the sister chromatids of each chromosome and pull them to opposite spindle poles

Front 98

What happens in telophase?

Back 98

Two clusters of chromosomes reach the spindle poles
A new nuclear envelope forms around each cluster
Two new nuclei are formed, each with the same chromosome number as the parent cell

Front 99

What is cytokenisis?

Back 99

The process of cytoplasmic division

Front 100

Describe cytokensis in animal and plant cells?

Back 100

Animal cells
A cleavage furrow partitions the cytoplasm
A band of actin filaments rings the cell midsection, contracts, and pinches the cytoplasm in two

Plant cells
A cell plate forms midway between the spindle poles; it partitions the cytoplasm when it reaches and connects to the parent cell wall

Front 101

What is the cell cycle?

Back 101

The sequence of stages through which a cell passes during its lifetime (interphase, mitosis, and cytoplasmic division) is called the cell cycle

Front 102

Mitosis is the basis of body size _____ and tissue ____ in multicelled eukaryotes; it is also the basis of asexual reproduction in single-celled and some multicelled eukaryotes

Back 102

increases; repair

Front 103

Most differentiated human cells are in ___– some types never progress past that stage

Back 103

G1

Front 104

When a cell divides is determined by ___ ___ ___; some cause the cell cycle to advance, others stop the cycle from proceeding

Back 104

gene expression controls

Front 105

There are three major checkpoints in the eukaryotic cell cycle, each regulated by protein complexes. What are they?

Back 105

G1 to S:
G2 to mitosis
Metaphase to anaphase

Front 106

_____ occurs in immature germ cells to create mature reproductive structures called gametes.

Back 106

Meiosis

Front 107

In asexual reproduction, there is no variation in offspring unless there is a ______.

Back 107

mutation

Front 108

A nuclear division mechanism that precedes cytoplasmic division of immature reproductive cells in sexually-reproducing eukaryotic species

Back 108

Meiosis

Front 109

In meiosis, DNA is replicated ___ and divided ___.

Back 109

once; twice

Front 110

Name 9 differences between meiosis and mitosis

Back 110