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Biology 30 > Cell Division: Chapter 10-12 > Flashcards

Cell Division: Chapter 10-12 Flashcards

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1
Q

Somatic cells

A

Any of the cells of a multicellular organism except those that form gametes.

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2
Q

Cell cycle

A

The life cycle of a cell. A single cell cycle is defined as the sequence of events from one cell division to the next. New cells that arise from cell division must be able to carry on the same function as the original cell.
- Lives of somatic cells vary, based on their type and environment.

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3
Q

What are the two stages of the cell cycle?

A

Growth stage and division stage.

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4
Q

Interphase

A

(AKA interphase)

  • Composed of three phases: GI, S and G2
  • Growth stage ends when the cell begins the process of nuclear division (mitosis)
  • Most of the cell’s life is spent in interphase
  • Cell carries out its regular metabolic functions and prepares for next division
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5
Q

Growth Stage: G1

A

First phase.
“Gap phase” as early scientists couldn’t find out what was happening. Turns out, important growth processes are occurring, therefore scientists renamed it “Growth 1”. Cell grows quickly.

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6
Q

Growth Stage: S phase

A

About midway through interphase, cell’s DNA is copied exactly. The DNA in the chromatin replicates to create a second set of DNA. The two identical chromosomes, called sister chromatids, are joined at the centromere. Since new genetic material is being synthesized, it is known as the S phase.

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7
Q

Growth Stage: G2

A

“Gap 2” or “Growth 2”. DNA replication in the S phase required a lot of energy, so G2 les cell rebuild its reserves of energy to prepare for division. Cell also manufactures proteins and other molecules to make structures required for division of the nucleus and cell.

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8
Q

Sister chromatids

A

Identical chromosomes that appear in the S phase of the growth stage. Connected at a centromere.

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9
Q

DNA

A

(Deoxyribonucleic acid) is a molecule of nucleic acid that governs processes of heredity in the cells of organisms. DNA is found in the chromosome of a cell.

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10
Q

Chromosome

A

Length of DNA and its associated proteins.
- In eukaryotic cells (cells that make up protists, fungi, plants, and animals. Have a membrane-bound nucleus.), the chromosomes are found in the nucleus (has a diameter of 5μm).

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11
Q

Histones

A

Highly organized protein found in chromosomes; acts as a scaffold around which DNA winds, enabling it to fit within the small space of the nucleus.

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12
Q

Chromatin

A

Long fibres that form chromosomes and contain DNA, a small amount of RNA, and various proteins, non-condensed form of genetic material that predominates for most of the cell cycle.

  • For most of a cell’s life cycle, its genetic material appears as a mass of long, intertwined strands (chromatin).
  • As genetic material is reorganized during the processes of cellular division, threads of chromatin condense and become visible under a light microscope as distinct chromosomes.
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13
Q

Haploid

A

Cell that contains unpaired chromosomes.

  • Stems from Greek word, meaning “single”.
  • Haploid # of chromosomes are designated as n.
  • Ex. Human gametes (sperm and egg cells), are haploid and n = 23.
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14
Q

Diploid

A

A cell that contains pairs of homologous chromosomes.

  • Stems from Greek word, meaning “double”.
  • Diploid cell has 2n chromosomes. (Ex. in humans, 2n = 46)
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15
Q

Autosomes

A

Chromosome other than a sex chromosome; human somatic cells have 22 pairs of these.
- Autosomes are numbered from 1 to 22.

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16
Q

Homologous chromosome

A

Chromosome that contains the same gene sequence as another, but that may not be made up of the same alleles; human somatic cells have 22 pairs (autosomes).

  • Females have homologous pair of X sex chromosomes
  • Males are not homologous, as men have an X and a Y sex chromosome
  • Homologous chromosomes carry the same genes at the same locus.
  • Homologous genes look the same, but are not identical to each other. They actually carry different alleles of the same gene.
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17
Q

Sex chromosome

A

X or Y chromosome that carries the genes involved in determining the genetic sex of an individual.

  • Each somatic cell has two sex chromosomes that may or not be a homologous pair.
  • Female has two X chromosomes
  • Male has one X chromosome and one Y chromosome (counted as a pair, even though it is not homologous).
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18
Q

Genes

A

Areas of DNA that contain specific genetic information.

- Homologous chromosomes carry the same genes at the same locus.

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19
Q

Locus

A

Specific location on a chromosome.

- Homologous chromosomes carry the same genes at the same locus.

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20
Q

Allele

A

Different form of the same gene occurring on homologous chromosomes.
- Homologous genes look the same but are not identical to each other. They actually carry different alleles of the same gene.

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21
Q

Steps in both mitosis and cytokinesis

A
  • Growth: Enable organisms to grow from a single-celled zygote into a mature organism that may contain hundreds of trillions of cells.
  • Maintenance: They produce new cells to replace worn out or dead cells.
  • Repair: They can regenerate damaged tissues. Some organisms are able to regenerate entire body parts that have been lost.
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22
Q

Functions accomplished in both mitosis and cytokinesis

A
  • Genetic material of parent cell must be replicated
  • Replicated chromatin must be condensed and organized as chromosomes in the nucleus
  • One complete set of chromosomes must be divided into each of two new nuclei
  • Cell cytoplasm must divide to produce two complete and functional daughter cells
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23
Q

Mitosis

A

One of the two main processes in cell division: division of the genetic material and the contents of the cell’s nucleus into two complete and separate sets; results in a daughter cell receiving the exact same number of chromosomes and genetic make-up as the parent cell.

  • In G2 (interphase), cell begins manufacturing/assembling other materials it will require for mitosis and cytokinesis.
  • Mitosis has a continuous sequence. The four main phases are identified by a characteristic arrangement of chromosomes and the appearance or disappearance of other cell structures
  • Mitosis produces cells with the same amount of DNA as what is started with. Occurs anytime an organism exhibits growth
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24
Q

Prophase in mitosis

A

First of the four phases of mitosis.

  • Chromatin condenses into tightly packed chromosomes
  • The nuclear membrane breaks down, releases chromosomes into the cytoplasm
  • Nucleolus disappears
  • Pair of centrioles (cylindrical organelles) moves to opposite poles of the cells and the spindle apparatus (network of fibres made up of microtubules - hollow tubes of protein) forms between them
  • Spindle apparatus facilitates movement of chromosomes within a cell
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25
Q

Metaphase in mitosis

A

Second phase of mitosis

  • Spindle apparatus guide the chromosomes to the equator of cell
  • Spindle fibres from opposite poles attach to the centromere of each chromosome
  • One sister chromatid faces one pole, while the other sister chromatid faces the opposite pole
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26
Q

Anaphase in mitosis

A

Third phase of mitosis

  • Centromere splits apart
  • Sister chromatids separate from one another
  • Spindle fibres that link the centromeres to the poles of the cells shorten
  • As fibres shorten, sister chromatids are pulled to opposite poles
  • Other microtubules in the spindle apparatus lengthen and force the poles of the cell away from one another
  • At the end of anaphase, one complete diploid set of chromosomes have been gathered at each pole
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27
Q

Telophase in mitosis

A

Fourth phase of mitosis

  • Chromatids at either end of the cell unwind into the longer and less visible strands of chromatin
  • Spindle fibres break down
  • Nuclear membrane forms around each new set of chromosomes, and a nucleolus forms within each new nucleus
28
Q

Cytokinesis

A

Follows mitosis. It’s the division of the cytoplasm to complete the creation of two new daughter cells
→ Cytokinesis in animals:
- Indentation forms in the cell membrane along the cell equator
- Indentation deepens until the cell is pinched in two
- Cytoplasm and organelles divide equally between the two halves of the cell
- Ends with two identical daughter cells, which are now in the G1 of interphase

29
Q

Mitosis and Cytokinesis in plants

A
  • Plants do not have centrioles, but do form a spindle apparatus
  • Cell wall of plant cell is much stronger than animal cell membrane. This cell wall does not indent and pinch during cytokinesis. Instead, a cell plate is formed between the two daughter nuclei and extends across the diameter of the cell, and is reinforced by cellulose to make a new cell wall
30
Q

Cell plate

A

Make in cytokinesis in plants.

Structure across a dividing plant cell that signals the location of new plasma membranes and cell walls

31
Q

Chromosome

A

Length of DNA and its associated proteins.
- In eukaryotic cells (cells that makeup protists, fungi, plants, and animals. Have a membrane-bound nucleus.), the chromosomes are found in the nucleus (has a diameter of 5μm).

32
Q

Cancer and tumor creation

A

Group of diseases associated with uncontrolled, rapid cell division
- Instead of spending most of their time in interphase, cancerous cells quickly move from one division to the next which results in a fast-growing mass of non-functional cells, called a tumour

33
Q

Function of mitosis

A
  • Growth: Enable organisms to grow from a single-celled zygote into a mature organism that may contain hundreds of trillions of cells.
  • Maintenance: They produce new cells to replace worn out or dead cells.
  • Repair: They can regenerate damaged tissues. Some organisms are able to regenerate entire body parts that have been lost.
34
Q

Two outcomes of meiosis

A

Reduction division: Form of cell division that produces daughter cells with fewer chromosomes than the parent cells
Recombination: Products of meiosis have a different combination of genes, which gives rise to offspring that are genetically distinct from one another and their parents

35
Q

Meiosis I: Prophase I

A
  • Synapsis: Homologous chromosomes align side by side and pair up
  • Tetrad: As chromosomes consists of two chromatids, a pair is made up of four chromatids which create a tetrad.
  • Non-sister chromatid: In the middle of a tetrad is two homologous but not identical chromatids, which are called non-sister chromatid, lie side by side (one chromatid from each pair)
36
Q

Meiosis I: Metaphase I

A
  • Spindle fibre attaches to the centromere of each chromosome
  • Spindle fibre from one pole attaches to one pair of sister chromatids in the tetrad
  • Spindle fibre from opposite pole attaches to the other pair of sister chromatids
  • Spindle fibres guide each tetrad to the equator of the cell
  • Chromosomes line up as homologous pairs, in each pair one homologous chromosome is positioned on one side of the cell’s equator, and the other homologous chromosome is positioned on the other side
37
Q

Meiosis I: Anaphase I

A
  • Spindle fibres shorten which causes the homologous chromosomes to separate from one another
  • Homologues move to opposite poles of the cell
  • Since the sister chromatids are still held together, the centromeres do not split (like they do in mitosis)
  • Results in a single chromosome made up of two sister chromatids from each homologous pair moves to each pole of the cell
38
Q

Meiosis I: Telophase I

A
  • Some cells move directly from anaphase I to meiosis II
  • Homologous chromosomes begin to uncoil
  • Spindle fibres disappear
  • Cytoplasm is divided
  • Nuclear membrane forms around each group of homologous chromosomes, and two cells are formed.
  • Each of these new cells contains one set of sister chromatids and is now haploid
39
Q

Meiosis II

A
  • Each cell that enters meiosis II is haploid but consists of replicated chromosomes
  • At the end of meiosis II, the daughter cells are still haploid, but they contain single unreplicated chromosomes
40
Q

Independent assortment

A

In metaphase I, chromosomes are arranged in homologous pairs along the equator. In each pair, the chromosome of maternal origin is oriented toward one pole of the cell while the chromosome of paternal organ is oriented toward the other pole. This orientation of each pair of homologous chromosomes is independent of the orientation of the other pairs. Therefore, some maternal homologues and some paternal homologues face each pole of the cell

41
Q

Crossing over

A

While homologous chromosomes are lined up side by side during prophase I, non-sister chromatids may exchange pieces of chromosome in a process known as crossing over.

  • A section of chromosome that is crossed over may contain hundreds or even thousands of genes. As a result of crossing over, individual chromosomes contain some genes of maternal origin and some genes of paternal origin.
  • Crossing can happen at many different locations on the non-sister chromatid
42
Q

Nondisjunction

A

Failure of homologous chromosomes pairs or sister chromatids to separate during meiosis I and meiosis II, respectively. (Specifically, during anaphase I and II.) This leads to gametes that have either too few or too many chromosomes.

  • Anaphase I: Nondisjunction occurs when homologous chromosome pairs do not separate to opposite poles and one entire pair is pulled to the same pole together
  • Anaphase II: Nondisjunction occurs when sister chromatids do not separate to opposite poles and both sister chromatids are pulled toward the same pole together
43
Q

Steps in meiosis: prophase I and II

A

Synapsis: Homologous chromosomes align side by side and pair up
Tetrad: As chromosomes consists of two chromatids, a pair is made up of four chromatids which create a tetrad.
Non-sister chromatid: In the middle of a tetrad is two homologous but not identical chromatids, which are called non-sister chromatid, lie side by side (one chromatid from each pair)

44
Q

Factors that regulate the cell cycle

A

→ Cells must divide only at certain times and must stop dividing at the correct time, a balance achieved by regulatory signals

  • Specific protein interactions “start” or “stop” signals for cell division
  • External factors also play a role (ex. presence of hormones, availability of nutrients, contact with other cells)
45
Q

Meiosis

A

The cellular process that produces haploid gametes from diploid cells in the ovaries and testes

46
Q

Two outcomes of meiosis

A

Reduction division: Form of cell division that produces daughter cells with fewer chromosomes than the parent cells
Recombination: Products of meiosis have a different combination of genes, which gives rise to offspring that are genetically distinct from one another and their parents

47
Q

Difference in meiosis and mitosis: Type of reproduction

A

Meiosis: Sexual
Mitosis: Asexual

48
Q

Difference in meiosis and mitosis: Genetically ___

A

Meiosis: Different
Mitosis: Identical

49
Q

Difference in meiosis and mitosis: Crossing over?

A

Meiosis: Yes, mine of chromosomes can occur
Mitosis: No, crossing over cannot occur

50
Q

Difference in meiosis and mitosis: Pairing of homologs?

A

Meiosis: Yes
Mitosis: No

51
Q

Difference in meiosis and mitosis: Number of daughter cells produced

A

Meiosis: 4 haploid cells
Mitosis: 2 diploid cells

52
Q

Independent assortment

A

In metaphase I, chromosomes are arranged in homologous pairs along the equator. In each pair, the chromosome of maternal origin is oriented toward one pole of the cell while the chromosome of paternal organ is oriented toward the other pole. This orientation of each pair of homologous chromosomes is independent of the orientation of the other pairs. Therefore, some maternal homologues and some paternal homologues face each pole of the cell

53
Q

Cohesins

A

a ring-shaped protein that holds sister chromatids together at the centromere region

54
Q

Condensins

A

a ring-shaped protein that holds DNA in loops, used to compact eukaryotic chromosomes

55
Q

Four proteins in meiosis

A

Cohesins, condensins, microtubules, and nuclear lamins

56
Q

Polar microtubules

A

microtubules that form during mitosis and meiosis and that extend from a spindle apparatus of and overlap with each other in the middle of the cell

57
Q

Kinetochore microtubules

A

microtubules that attach to the centromere

58
Q

Kinetochore

A

a protein structure at the centromere where kinetochore microtubules attach to the sister chromatids of a replicated chromosome

59
Q

Prometaphase

A

Nuclear envelope breaks down and kinetochore microtubules attach to kinetochores on chromosomes (in between prophase and metaphase)

60
Q

Cleavage furrow

A

a pinching-in of the plasma membrane that occurs as cytokinesis begins in animal cells and deepens until the cytoplasm is divided

61
Q

Mitosis promoting factor (MPF)

A

a complex of a cyclin and cyclin-dependent kinase that phosphorylates a number of specific proteins needed to initiate mitosis in eukaryotic cells
- deactivated by negative feedback

62
Q

Cyclins

A

one of several regulatory proteins whose concentrations fluctuate cyclically throughout the cell cycle

63
Q

Cyclins-dependent kinase (Cdk)

A

any of several related protein kinases that are active only when bound to a cyclin, involved in control of the cell cycle

64
Q

Synapsis

A

Homologous chromosomes pairing together

65
Q

Tetrad

A

Pair of homologous

66
Q

Chiasma

A

X-shaped structure formed during meiosis by crossing over between non-sister chromatids in a pair of homologous chromosomes

Biology 30 (7 decks)

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