Bio 188: Study Guide Four

Front 1

Distinguish between fission and mitosis.

Back 1

Fission is the reproduction of a prokaryote by division of a cell into two comparable progeny cells while mitosis is nuclear division in eukaryotes leading to the formation of two daughter nuclei, each with a chromosome complement identical to that of the original nucleus.

Front 2

Describe the four phases of the cell cycle.

Back 2

The cell cycle consists of four distinct phases: G1 phase, S phase (synthesis), G2 phase (collectively known as interphase) and M phase (mitosis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's chromosomes are divided between the two daughter cells, and cytokinesis, in which the cell's cytoplasm divides forming distinct cells. Activation of each phase is dependent on the proper progression and completion of the previous one. Cells that have temporarily or reversibly stopped dividing are said to have entered a state of quiescence called G0 phase. They are described in the terms below.

Front 3

What is G0?

Back 3

The G0 phase (G sub 0) is a period in the cell cycle where cells exist in a quiescent state. G0 is sometimes referred to as a "post-mitotic" state since cells in G0 are in a non-dividing phase outside of the cell cycle. Cells enter the G0 phase from a cell cycle checkpoint in the G1 phase, such as the restriction point (animal cells) or the start point (yeast). During the G0 phase, the cell cycle machinery is dismantled and cyclins and cyclin-dependent kinases disappear. Cells then remain in the G0 phase until there is a reason for them to divide.

Front 4

Where are the checkpoints located in the cell cycle? What is the purpose of check points?

Back 4

5 checkpoints: restriction checkpoint controlled by growth factors, DNA damage checkpoints in late G1 and S, DNA replication checkpoint in late G2, spindle checkpoint in M checks for prper spindle attachment. The purpose is

Front 5

What is the function of kinase?

Back 5

It is an enzyme that transfers a phosphate group from ATP to another molecule. Protein kinases transfer phosphate from ATP to specific proteins, playing important roles in cell regulation.

Front 6

What are the phases of mitosis? What are the distinguishing features of each phase?

Back 6

The phases of mitosis are interphase, preprophase, prophase, prometaphase, metaphase, anaphase, and telophase. They are described in the terms below.

Front 7

What are chromatids? How many chromatids does a homologous pair of chromosomes have?

Back 7

Chromatids are each pair of new sister chromosomes from the time at which the molecular duplication occurs until the time at which the centromeres separate at the anaphase of nuclear division. Each homologous pair of chromosomes have two sister chromatids.

Front 8

What are homologous chromosomes?

Back 8

One of a pair of chromosomes having the same overall genetic composition and sequence. In diploid organisms, each chromosome inherited from one parent is matched by an identical chromosome from the other parent.

Front 9

Distinguish between mitosis and meiosis.

Back 9

Meiosis is the division of a diploid nucleus to produce four haploid daughter cells. The process consists of two successive nuclear divisions with only one cycle of chromosome replication. In meiosis I, homologous chromosomes separate but retain their chromatids. The second division meiosis II, chromatids separate. Mitosis is the nuclear division in eukaryotes leading to the formation of two daughter nuclei, each with a chromosome complement identical to that of the original nucleus.

Front 10

Distinguish between anaphase I and anaphase II of meiosis.

Back 10

In anaphase I the chromatids holding the chromosomes together loosen. The two homologous chromatids of each tetrad are separated into separate poles. Anaphase II separates the dyads into individual chromatids. Each sister chromatid ends up on one side of the cell.

Front 11

What is the role of the centrosome in cell division?

Back 11

The major microtubule organizing center of an animal cell.

Front 12

What is the role of the centromere in mitosis?

Back 12

It the location where the sister chromatids join.

Front 13

When do chromatids separate in mitosis? When do chromatids separate in meiosis?

Back 13

Chromatids separate in meiosis II and in mitosis at anaphase.

Front 14

Define: Anaphase

Back 14

The stage in nuclear division at which the first separation of sister chromatids occurs.

Front 15

Define: Histone protein

Back 15

Any one of a group of basic proteins forming the core of a nucleosome, the structural unit of a eukaryotic chromosome.

Front 16

Define: Anaphase I

Back 16

the chromatids holding the chromosomes together loosen. The two homologous chromatids of each tetrad are separated into separate poles.

Front 17

Define: Homologous chromosome

Back 17

One of a pair of chromosomes having the same overall genetic composition and sequence. In diploid organisms, each chromosome inherited from one parent is matched by an identical chromosome from the other parent.

Front 18

Define: Anaphase II

Back 18

Anaphase II separates the dyads into individual chromatids. Each sister chromatid ends up on one side of the cell

Front 19

Define: Interphase

Back 19

The period between successive nuclear divisions during which the chromosomes are diffuse and the nuclear envelope is intact. It is during this period that the cell is most active in transcribing and translating genetic information. G1, S, and G2 phase.

Front 20

Define: Cell cycle

Back 20

The stages through which a cell passes between one division and the next. Includes all stages of interphase and mitosis.

Front 21

Define: M Phase

Back 21

The portion of the cell cycle in which mitosis take place.

Front 22

Define: Centromere

Back 22

The region where sister chomatids join.

Front 23

Define: Meiosis

Back 23

Division of a diploid nucleus to produce four haploid daughter cells. The process consists of two successive nuclear divisions with only one cycle of chromosome replication. In meiosis I, homologous chromosomes separate but retain their chromatids. The second divison meiosis II, chrmatids separate.

Front 24

Define: Centrosome

Back 24

The major microtubule organizing center of an animal cell.

Front 25

Define: Metaphase

Back 25

The stage in nuclear division at which the centromeres of the highly supercoiled chromosomes are all lying on a plane perpendicular to a line connecting the division poles.

Front 26

Define: Chromatid

Back 26

Each pair of new sister chromosomes from the time at which the molecular duplication occurs until the time at which the centromeres separate at the anaphase of nuclear division.

Front 27

Define: Metaphase I

Back 27

Homologous chromosomes pair with each other to form tetrads of four chromatids and they align themselves along a single plane in the centre of the cell. Homologous recombination generally occurs during this stage. This stage ends as soon as the homologous chromosomes start being pulled away from each other, to opposite ends of the cell.

Front 28

Define: Chromosome

Back 28

In bacteria and viruses, the DNA molecule that contains most or all of the genetic information of the cell or virus. In eukaryotes, a structure composed of DNA and proteins that bears part of the genetic information of cells.

Front 29

Define: Metaphase II

Back 29

The chromosomes become arranged on the metaphase plate, much as the chromosomes do in mitosis, and are attached to the now fully formed spindle.

Front 30

Define: Cyclin

Back 30

Proteins that activate cyclin-dependent kinases, bringing about transitions in the cell cycle.

Front 31

Define: Mitosis

Back 31

Nuclear division in eukaryotes leading to the formation of two daughter nuclei, each with a chromosome complement identical to that of the original nucleus.

Front 32

Define: Cyclin dependent kinase (Cdk)

Back 32

A kinase whose target proteins are involved in the transitions in the cell cycle and which is active only when complexed with additional protein subunits, called cyclins.

Front 33

Define: Mitotic spindle

Back 33

The array of microtubules and associated proteins that forms between the opposite poles of a eukaryotic cell during mitosis and serves to move the duplicated chromosomes apart.

Front 34

Define: Cytokinesis p21 protein

Back 34

Stops the cell cycle by blocking Cyclin D .

Front 35

Define: Daughter chromosome

Back 35

During mitosis, the separated chromatids from the beginning of anaphase onward.

Front 36

Define: Prophase

Back 36

The first stage of nuclear division, during which chromosomes condense from diffuse, threadlike material to discrete, compact bodies.

Front 37

Define: Diploid

Back 37

Having a chromosome complement consisting of two copies (homologs) of each chromosome. Designated 2n.

Front 38

Define: Pro-metaphase

Back 38

The phase of mitosis following prophase and preceding metaphase, in eukaryotic somatic cells. The nuclear envelope breaks into fragments and disappears. Microtubules emerging from the centrosomes at the poles (ends) of the spindle reach the chromosomes, now highly condensed. At the centromere region, each sister chromatid has a protein structure called a kinetochore. Some of the spindle microtubles attach to the kinetochores, throwing the chromosomes into agitated motion. Other spindle microtubules make contact with microtubules coming from opposite pole. Forces exerted by protein "motors" associated with spindle microtubules move the chromosomes toward the center of the cell.

Front 39

Define: Fission

Back 39

The phase of mitosis following prophase and preceding metaphase, in eukaryotic somatic cells. The nuclear envelope breaks into fragments and disappears. Microtubules emerging from the centrosomes at the poles (ends) of the spindle reach the chromosomes, now highly condensed. At the centromere region, each sister chromatid has a protein structure called a kinetochore. Some of the spindle microtubles attach to the kinetochores, throwing the chromosomes into agitated motion. Other spindle microtubules make contact with microtubules coming from opposite pole. Forces exerted by protein "motors" associated with spindle microtubules move the chromosomes toward the center of the cell.

Front 40

Define: Prophase I

Back 40

The two homologs are joined, forming two homolgous chromosomes with two sister chromatids.

Front 41

Define: Prophase II

Back 41

The chromosomes become visible, the nuclear envelope disappears and the centrioles form the spindle fibres.

Front 42

Define: G1

Back 42

In the cell cycle, the gap between the end of mitosis and the onset of the S phase; cell growth

Front 43

Define: retinoblastoma (RB) protein

Back 43

A protein that inhibits an animal cell from passing through the restriction point; inactivation of this protein is necessary for the cell cycle to proceed.

Front 44

Define: G2

Back 44

In the cell cycle, the gap between the S (synthesis) phase and the onset mitosis.

Front 45

Define: S Phase

Back 45

In the cell cycle, the stage of interphase during which DNA is replicated.

Front 46

Define: Haploid

Back 46

Having a chromosome complement consisting of just one copy of each chromosome; designated 1n or n.