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Biology I > Chapter 11 - The Cell Cycle and Cell Division > Flashcards

Chapter 11 - The Cell Cycle and Cell Division Flashcards

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1
Q

Cell division

A

Important in growth and repair of tissues in multicellular organisms and in the reproduction of all organisms

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2
Q

Binary fission

A

In prokaryotes, binary fission results in two new single-celled organisms; external factors such as nutrient concentration and environmental conditions are the reproductive signals; mitochondria and chloroplasts also divide through binary fission

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3
Q

4 events must occur for cell division

A

1) Reproductive signal that initiates cell division
2) Replication of DNA
3) Segregation of DNA to each new cell
4) Cytokinesis

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4
Q

Prokaryotic DNA replication

A

Prokaryotes have one single circular chromosome; the DNA is fed through a replication complex of proteins and begins at the ori (origin of replication) and moves toward the ter (terminus of replication); when replication is complete, the daughter DNA molecules are segregated at opposite ends; the plasma membrane pinches and new cell wall materials are synthesized, separating the two cells

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5
Q

Cell cycle

A

Period from one cell division to the next; compromised of mitosis, cytokinesis and interphase

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6
Q

Interphase

A

Cell nucleus is visible and typical cell functions occur, including DNA replication; begins right after cytokinesis and end when mitosis starts; cell spends most of its time in interphase: includes 3 subphases: G1, S and G2 phase

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7
Q

G0 phase

A

Metabolically active cell that is in a resting phase from the cell cycle; cells that generally do not divide go into an extended “G1” phase

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8
Q

G1 phase

A

Gap or growth phase; normal metabolizing stage of the cell; chromosomes are single, unreplicated DNA

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9
Q

S phase

A

Synthesis phase, where DNA replication occurs (DOES NOT occur in mitosis); at the end of S phase, double the amount of chromosomes are available and the sister chromatids remain together; forms two centrosomes (4 centrioles)

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10
Q

G1-to-S transition

A

Commitment is made to replicate DNA and subsequent cell division; aka restriction (R) point or checkpoint before moving forward

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11
Q

G2 phase

A

Cell prepares for cell division; microtubules and enzymes specific for cell division are formed; aka restriction (R) point or checkpoint before moving forward

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12
Q

Cyclin-dependent kinases (Cdk’s)

A

Inactive kinases on its own and always present, dependent on the presence of the protein cyclin (produced when needed); cyclin binds to the protein kinase at an allosteric site, changing the shape and exposing the active site; directs the Cdk to a specific set of target proteins, ones appropriate to the cell cycle period controlled by the cyclin; signals that trigger transition from one phase of cell division to another; variety of cyclin molecules to activate certain phases of the cell cycle; the enzyme protease will degrade the cyclin protein to return the kinase back to its inactive state

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13
Q

Retinoblastoma (RB) protein

A

At the G1-to-S transition, RB inhibits the cell cycle, but is phosphorylated by a cdk, becoming inactive and the cell cycle then continues

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14
Q

Maturation Promoting Factor (MPF)

A

The cyclin-cdk complex that functions together to initiate phases in the cell cycle

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15
Q

Growth factors

A

External chemical signals that stimulate cell division (especially for cells that no longer go through the cell cycle or enter G0 phase); ie. platelets release a protein called platelet-derived growth factor that diffuses to adjacent cells in the skin and stimulates them to divide to heal the wound; interleukin and erythropoietin stimulate the division and specialization of precursor white and red blood cells

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16
Q

Chromatin

A

DNA molecules coupled with proteins

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17
Q

Condensins

A

Proteins that coat the DNA molecules that are separated during anaphase of mitosis and compacts the DNA

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18
Q

Chromosome

A

Well-defined, linear double stranded DNA molecules bound with proteins

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19
Q

Sister chromatids

A

Chromosomes are replicated and joined together by cohesin to form 2 sister chromatids (each pair is considered one chromosome); when the sister chromatids are separated during anaphase of mitosis, each sister chromatid becomes one chromosome

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20
Q

Nucleosome

A

Beadlike units that are composed of DNA and histones that are tightly compacted together; DNA with a net negative charge attracts to the net positive histones

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21
Q

Histones

A

A nucleosome is composed of 8 protein molecules (histone octamers) that is wrapped by DNA 2x; H1 histone located outside of the octamer links the DNA to the octamer to keep the nucleosome structure in place

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22
Q

Mitosis

A

The process of a single nucleus that gives rise to two nuclei that are genetically identical to each other and to the parent nucleus

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23
Q

Prophase

A

2 centrosomes (4 centrioles) move to opposite poles; sister chromatids become more visible and the nuclear envelope becomes faint

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24
Q

Prometaphase

A

Nuclear envelope breaks down, the sister chromatids are attached to the spindle apparatus and spindle formation is completed, centrosomes are at opposite poles

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25
Q

Metaphase

A

Sister chromatids are lined up at the midline of the cell along the metaphase plate

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26
Q

Anaphase

A

The sister chromatids separate, now becoming separate chromosomes and move away toward opposite poles; total of 92 chromosomes, 46 at each end of the cell

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27
Q

Kinetochore microtubules

A

Microtubules that attach to the chromosome at the centromere during mitosis; moves chromosomes to opposite poles by depolymerizing or shortening to separate the sister chromatids

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28
Q

Nonkinetochore (polar) microtubules

A

Microtubules that elongate whole cell during anaphase of mitosis

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29
Q

Centromere

A

Region that binds the two sister chromatids together that is comprised of a non-coding DNA sequence that is recognized by the kinetochore complex

30
Q

Kinetochore

A

Assemblage of proteins that bind to the centromeric region of the sister chromatids; kinetochore microtubules bind to the chromatids at this region

31
Q

Separase

A

Enzyme that hydrolyzes the cohesin protein that holds the sister chromatids together at the end of metaphase

32
Q

Anaphase-promoting complex (APC)

A

Separation of sister chromatids is controlled by the M-phase cyclin-cdk; APC activates separase to hydrolyze cohesin and separate the sister chromatids

33
Q

Spindle assembly checkpoint

A

A cell cycle checkpoint at the end of metaphase that verifies that all sister chromatids are properly attached to the spindle; if properly attached, anaphase-promoting complex is activated, cohesin is removed and the chromatids are separated

34
Q

Telophase

A

Reformation of the nuclear envelopes and endomembrane organelles; chromosomes become less compact

35
Q

Cytokinesis

A

A cleavage furrow is formed from the pinching of the cell, contractile ring composed of actin and myosin shrinks and contracts to pinch the cell into two

36
Q

Function of meiosis

A

To generate genetic diversity, to reduce chromosome number from diploid to haploid and to ensure each haploid has a complete set of chromosomes

37
Q

Somatic cells

A

Cells not specialized for reproduction; each cell contain two sets of chromosomes (one set from each parent (2n)

38
Q

Gametes

A

Sex cell that contains only a single set of chromosomes; considered a haploid cell (n)

39
Q

Zygote

A

2 haploid gametes fuse to form a diploid zygote with two sets of chromosomes

40
Q

Homologous pairs

A

Each somatic cell contains homologous pairs of chromosomes; homologous chromosomes are similar but not identical, each carries the same genes in the same order, but the alleles for each trait may not be the same; one chromosome of each homologous pair comes from the mother (called a maternal chromosome) and one comes from the father (paternal chromosome)

41
Q

Gene

A

Segment of DNA that provides instructions for building a protein that determines the observable features of an organism; program specific traits

42
Q

Karyotype

A

Ordered display of an individual’s chromosomes; shows homologous pairs of chromosomes; can aid in the diagnosis of chromosomal abnormalities

43
Q

Diploid cell

A

A cell containing two sets of chromosomes (2n) or 46 chromosomes

44
Q

Haploid cell

A

A cell containing one set of chromosomes (n) or 23 chromosomes

45
Q

Meiosis

A

Formation of gametes containing a haploid set (n) of chromosomes for the purpose of reproduction; 2 nuclear divisions that together reduce the number of chromosomes to the haploid number; DNA is replicated ONCE

46
Q

Meiosis I

A

Homologous pairs separate but individual chromosomes (2 sister chromatids) remain intact

47
Q

Synapsis

A

During prophase I, homologous chromosomes pair by adhering along their lengths; chromosomes of maternal origin pair with their paternal homologs, forming a tetrad

48
Q

Crossing over

A

During prophase I, exchange of genetic material occurs between non-sister chromatids at the chiasmata (x-shaped appearance of the tetrad), the site of cross over; results in recombinant chromatids

49
Q

Independent assortment

A

Matter of chance at which of a homologous pair goes to which daughter cell during anaphase I; depends on the way the homologous pairs line up at metaphase I; promotes genetic diversity

50
Q

Meiosis II

A

Sister chromatids are separated to form 4 haploid daughter cells (n); not preceded by DNA replication; stages are very similar to mitosis

51
Q

Origins of genetic variation via meiosis

A

1) Crossing over between non-sister chromatids during prophase I 2) Independent assortment during anaphase I 3) Random fertilization where a random egg fertilizes with a random sperm 4) Mutations

52
Q

Nondisjunction

A

Homologous pairs fail to separate at anaphase I or sister chromatids fail to separate at anaphase II

53
Q

Aneuploidy

A

Due to nondisjunction (failure for homologous pairs or chromosomes to separate), the haploid cells result in excess or lacking chromosomes; generally not viable cells; may be caused by a lack of cohesins that hold the homologous pairs together

54
Q

Translocation

A

A piece of chromosome may break away and become attached to another chromosome during meiosis

55
Q

Polyploid

A

Organisms with complete extra sets of chromosomes resulting from nondisjunction of all chromosomes during meiosis I; triploid (3n), tetraploid (4n), etc; typical of crop plants where cells tend to be larger

56
Q

Cancer cells

A

Lose control over cell division and the growth control mechanism is bypassed and can migrate to other parts of the body and establish new tumors (metastasis); no anchorage dependence and no density-dependent inhibition (the termination of cell division during overcrowding)

57
Q

Metastasis

A

Cancer cells migrate to other parts of the body and establish malignant tumors

58
Q

Tumor

A

Solid or diffuse masses of dedifferentiated cells

59
Q

Benign tumor

A

Tumor that is unable to metastasize; cells are differentiated and holds the characteristics of a differentiated functional cell

60
Q

Cancer genes code for

A

Growth factors, growth factor receptors, intracellular signaling molecules and telomerase to enable the cancer cell to continuously divide

61
Q

Angiogenesis

A

Malignant cancer cells signal the formation of new blood vessels to aid in cancer cell growth

62
Q

Hayflick limit

A

Normal cells have a limited number of divisions, usually about 50 per lifespan; telomeres associated with each cell’s DNA will get slightly shorter with each new cell division until they shorten to a critical length and die

63
Q

Gene alterations resulting in the formation of cancers

A

Spontaneous mutations or environmentally-induced mutations: chemical carcinogens, x-rays, certain viruses (tumor viruses - ie. HPV)

64
Q

Oncogenes

A

Mutated proto-oncogenes: a normal cellular gene that encodes a protein usually involved in regulation of cell growth or proliferation and that can be mutated into a cancer-promoting oncogene, either by changing the protein-coding segment or by altering its expression; produce proteins that are positive regulators in cancer cells and result in expression of oncoprotein at the wrong time, overexpression of oncoprotein, hyperactive oncoproteins

65
Q

Tumor suppressors

A

Negative regulators such as retinoblastoma (RB) (inhibits cell cycle at the G1-to-S transition during interphase) and p53 (inhibits cell division during cell cycle checkpoints) become inactive in cancer cells; ie. HPV produces a protein that inactivates RB

66
Q

Knudson’ Two-Hit Hypothesis

A

Formulated the idea of “genetic predisposition” to a specific cancer vs sporadic development of cancer; suggested that the first mutation was inherited in the DNA, and any second mutation would rapidly lead to cancer

67
Q

Necrosis

A

Cell death in which cell tissues are damaged by mechanical means or toxins or are starved of oxygen or nutrients; the cell swells and bursts, releasing its contents into the extracellular environment and causes inflammation

68
Q

Apoptosis

A

Programmed cell death where either the cell is no longer needed or the cells have reached an old age and are prone to cancer; the cell detached from its neighbors, chromatin is digested, form membranous lobes called “blebs” that break into fragments that are ingested by surrounding living cells

69
Q

Blebbing

A

A result of apoptosis in which fragments of the cells form membranous lobes that are ingested and recycled by surrounding living cells

70
Q

Signals that initiate apoptosis

A

Hormones, growth factor, viral infections, toxins, extensive DNA damage

71
Q

Capase

A

Protease enzyme that is activated during apoptosis that hydrolyzes membrane proteins in the nuclear envelope, nucleosomes, and plasma membrane

72
Q

Cancer treatments

A

Surgical removal of benign tumor, drugs that prevent cell division; chemotherapy (stops the mitotic spindle from progressing, terminating cell division), radiation treatment (beam of high energy radiation damages the DNA of the cancer cells and the cancer cells undergo apoptosis), oncolytic virotherapy (uses modified viruses to attack cancer cells)

Biology I (12 decks)

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