Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology > 5 Mitotic cycle > Flashcards

5 Mitotic cycle Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

General info on the mitotic cycle

A
  • When body cells reach a certain size they divide into two cells.
  • Nuclear division occurs first, followed by division of the cytoplasm.
  • The mitotic cell cycle of eukaryotes involves DNA replication followed by nuclear division. - This ensures the genetic uniformity of all daughter cells.
  • During cell cycle both mass of DNA and mass of cell as whole changes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How do cells divide?

A
  • All cells arise from existing cells by division.
  • Division occurs in two main stages: nuclear division (mitosis, meiosis) and cytokinesis (cell division)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Mitosis

A
  • Results in two daughter nuclei that are identical to parent nuclei.
  • Diploid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Meiosis

A
  • Four daughter nuclei with half the number of chromosomes as parent nucleus.
  • Haploid
  • Nuclei have a different genetic composition to parent one.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Cytokinesis (cell division)

A

Whole cell divides, cytoplasm is shared out.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the three stages of the mitotic cell cycle (overview?)

A

Interphase
- G1 phase
- Synthesis
- G2 phase

Mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase

Cytokinesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How long is a cell cycle typically?

A

Typically, cell cycle of mammalian cell is 24 hours.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe interphase

A
  • Longest phase of cell cycle.
  • Sometimes known as resting phase as no division is occurring.
  • Intense period of chemical activity.
  • G1, S and G2 phases.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

G1

A
  • Proteins (enzymes) and organelles are synthesised, and biochemicals produced.
  • Great quantity of mRNA for polypeptide synthesis at ribosomes (preparing for transcription and translation).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

S

A
  • DNA is replicated.
  • After replication each interphase chromosome is composed of two identical sister chromatids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

G2

A
  • Further protein synthesis.
  • Energy stores increased. Replication of centriole pair completed in animal cells.
  • Large store of microtubules (9 + 2 microtubule arrangement see Chapter 1). for formation of spindle.
  • Centriole replication complete
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the concept of “checkpoints” during the mitotic cell cycle?

A
  • As cell goes through mitotic cell cycle it has to reach and pass ‘quality control’ checkpoints which check for any kind of defects.
  • G1: If DNA is damaged the cell cycle will slow so that it can be repaired.
  • If DNA can’t be repaired cell death is triggered.
    -This system is not 100% foolproof, and where DNA has not been checked properly sometime mutations can occur or lead to tumour formation.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the structure of chromosomes:

A
  • Only visible when a cell is dividing – otherwise just see a mass of darkly staining chromatin.
  • When first visible appear as long, thin threads around 50 um.
  • Two identical sister chromatids joined by a centromere in the middle.
  • Capped with telomeres.
  • Highly coiled and folded, held in place by histone proteins.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Chromosome is made mainly up of:

A
  • Histone proteins (70%)
  • DNA (15%), about 2m each cell
  • Chromatin (complex formed from histone proteins and DNA, beaded appearance).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Nucleosome

A

portion of DNA that is: 146 base pairs wrapped around histone proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why do telomeres prevent the loss of genes from the ends of chromosomes?

A
  • Telomeres protect genes further along chromosome as they “cap” the end and do not contain genetic information.
  • Means that during cell division when replication enzymes cant reach end of chromosome telomere section is eroded and no actual genetic information is lost.
  • Length of telomere determines the life span of a cell/cellular aging. The longer a telomere is, the more a cell can divide, more a cell can divide and replicate, the longer it lives.
  • Telomeres can be lengthened in dividing cells through enzyme telomerase.
  • Telomerase is not present in non-dividing cells.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Telomere

A

a sequence of nucleotide bases repeated many times at the end of a chromosome (a “cap” of sorts).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why do cancer cells produce more telomerase

A

so that cells can divide more rapidly and live longer (tumor is uncontrolled cell division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Karytotype

A

photographical organisation of chromosomes cut out and pasted into logical format, showing full diploid set.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Uses of mitosis (overview)?

A
  • Growth of multicellular organisms
  • Cell replacement
  • Tissue repair
  • Asexual reproduction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does mitosis facilitate growth of multicellular organisms?

A
  • Cells divide by mitosis to produce new cells of the same kind. In any given cell entire genome is present but only certain gene(s) being expressed.
  • Some cells can differentiate to become specialized cells e.g., xylem cells in plants and muscle cells in animals.
  • All cells must be replicated to be genetically identical so that new cell can perform sam function and have same structure.
  • Mitosis therefore facilitates the growth of a multicellular organism through increasing the number of cells.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Why can mitosis be said to produce “genetically identical” but not “identical” cells?

A

During cytokinesis cytoplasm and organelles may be unequally distributed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does mitosis facilitate cell replacement?

A

Allows new cells to be produced to replace damaged or “dead” cells. E.g., a red blood cell only has a life span of 120 days.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How does mitosis facilitate the repair of tissues?

A
  • Allows genetically identical new cells to be produced that perform same structure and function as damaged tissue so that tissue can continue to function effectively.
  • Replaces damaged cells.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How does mitosis facilitate asexual reproduction?

A
  • Mitosis is how certain organisms carry out asexual reproduction, and in doing so create “clones” of themselves.
  • In eukaryotes mitosis IS asexual reproduction.
26
Q

Advantages of asexual reproduction

A
  • Parents well adapted to current environment so conditions for offspring should be well-suited and favorable too – as long as conditions do NOT change. E.g., a disease could wipe out whole population at once because no genetic variation.
  • Rapid form of reproduction – large numbers can be built up quickly to form a population.
  • The whole area can be colonized by this species and species can gain competitive advantage – especially for light by this means.
  • if offspring is not genetically identical could be due to a mutation.
  • bacteria do not produce by mitosis but binary fission.
27
Q

Adult stem cells

A
  • undifferentiated, continuously dividing cells that occur in animal tissues. E.g., found in inner lining of small intestine, in skin, in lining of gas exchange system, in bone marrow.
  • stem cells cannot divide indefinitely
28
Q

How do daughter stem cells work?

A
  • the genetically identical undifferentiated daughter cells of stem cells can divide to produce even more adult stem cells.
  • When necessary a daughter cell can differentiate and become specialised for a specific role and therefore serve as a replacement for damaged cells.
29
Q

Why are adult stem cells not completely undifferentiated

A
  • adult stem cells can only specialise/develop into cell type/types in the specific region they are located.
  • They are therefore not completely undifferentiated
30
Q

Where are stem cells found?

A
  • Adult stem cells found in mature organisms.
  • Embryonic stem cells occur at earliest stage of development of an embryo.
  • Embryonic stem cells are completely undifferentiated and can divide an infinite number of times.
31
Q

How does mitosis work in malignant tumours?

A
  • faster rate of division
  • when malignant tumour cells are carried into bloodstream they can invade/infiltrate other healthy tissues and form secondary or metastatic tumours
32
Q

How does mitosis work in benign tumours?

A
  • grow in a contained area (encapsulated) with a slower rate of division.
  • Do not infiltrate surrounding tissue
33
Q

How does mitosis enable tumour formation and how are tumours formed?

A
  • Formation of tumour occurs through uncontrolled cell division, which can be caused by the damage of genes that regulate mitosis.
  • Proto-oncogenes can mutate and become oncogenes. This causes the cell to continue to grow and divide.
  • Tumour suppressor genes (regulate cell division) can become switched off as a result of mutation.
  • Common mutagens – radiation. (check with chapter 6).
  • Checkpoints that regulate and control mitosis do not function properly in tumour cells.
  • Tumour cells do not undergo apoptosis (programmed cell death) and can live indefinitely.
  • Cells become less differentiated with each division. Lose ability to function properly.

All these factors combine to cause group of abnormal cells to form. This is called a tumour.

  • Healthy cells stop functioning when coming into contact with cells, known as contact-inhibition.
  • Tumour cells are not affected by contact-inhibition so they keep growing and expanding.
  • Tumours can be cancerous (malignant) or benign. Can develop in any part of body.
  • Can occur in plants too.
34
Q

Tumour

A

group of abnormal cells

35
Q

Contact-inhibition

A

when healthy cells come into contact with other cells and stop functioning.

36
Q

Apoptosis

A

programmed cell death

37
Q

Brief description of mitotic cell stages?

A

Prophase – chromosomes become visible and nuclear envelope disassembles.

Metaphase – chromosomes arrange themselves at equator (also known as metaphase plate) of cell.

Anaphase – sister chromatids move to opposite poles, thus becoming known as daughter chromosomes (because now separate entities).

Telophase – nuclear envelope reforms.

38
Q

What happens during prophase?

A
  • Chromosomes first become visible as long thin threads.
  • Chromosome condensation occurs (chromosomes shorten and thicken, DNA molecule in each chromatid coils and supercoils).
  • Animal cells: two pairs of centrioles separate and each pair moves to opposite poles.
  • Nucleolus disappears and nuclear envelope disassembles by breaking up into vesicles. This leaves chromosomes dispersed at random free in cytoplasm of cell.
  • Chromosomes become attached to microtubules of spindle fibres by centromere and are moved towards the equator (latter half of prophase).
39
Q

Centrosome

A
  • made up of 2 pairs of centrioles
40
Q

Spindle fibres

A
  • From each pair of centrioles microtubules develop and form spindle fibres.
  • Spindle fibred span cell from pole to pole.
  • collectively microtubules are known as spindle apparatus/spindle
41
Q

Coiling

A

refers to the wrapping of DNA around histone proteins to form nucleosomes and the subsequent organization into higher-order structures like the 30 nm chromatin fiber

42
Q

Supercoiling

A
  • refers to the additional twisting of the DNA double helix beyond its normal helical structure, leading to either over-winding (positive supercoiling) or under-winding (negative supercoiling)
  • resulting in a more compact structure, which is crucial for the efficient condensation of chromosomes during prophase in mitosis.
43
Q

What happens during metaphase?

A
  • Spindle is fully formed.
  • Chromosomes are arranged at spindle equator (get pulled by spindle fibres attaching to centromere and REMAIN attached in metaphase).
  • Sister chromatids remain attached to one another.
44
Q

What happens during anaphase?

A
  • Centromeres divide into two and spindle fibres joined to either side of (now divided) centromere contract, pulling sister chromatids apart and to opposite poles of cell.
  • Chromatids are now known as daughter chromosomes.
  • A lot of energy is needed for this process and is provided by mitochondria gathered around spindle fibres.
45
Q

How do chemicals aiming to stop mitosis work?

A
  • could target and destroy the spindle fibres.
  • This would ensure that the chromosomes remain at the equator unable to reach the poles
46
Q

What happens during telophase?

A
  • Daughter chromosomes reach their poles and become longer and thinner (opposite of chromosome condensation), eventually becoming chromatin again.
  • Spindle disassembles.
  • Nuclear envelope reassembles (the vesicles which were formed in prophase fuse back together again).
  • Nucleolus reforms.
  • Two separate nuclei can now be seen.
  • cytokinesis frequently begins before the end of telophase
47
Q

What happens during cytokinesis in animal cells?

A
  • Cleavage furrow forms and cytoplasm constricts to pinch the cell into two new cells.
  • Cell organelles are shared out between two cells (however this does not always happen equally so even though cells will be genetically identical they might not always be identical).
48
Q

What happens during cytokinesis in plant cells?

A
  • No cleavage furrow forms.
  • Organelles shared out.
  • Vesicles from Golgi body bring materials to form a cell plate across the equator of parent cell from centre outwards.
  • Cellulose laid down along this dividing plate to form a cell wall.
49
Q

What are the differences of nuclear and cell division between plant and animal cells?
Animal cells:

A
  • Stem cells able to divide by mitosis.
  • Stem cells occur where there is a requirement for growth, tissue repair and cell replacement.
  • Mitosis occurs in nucleus of cell (until nucleus in dissolved).
50
Q

What are the differences of nuclear and cell division between plant and animal cells?
Plant cells:

A
  • Mitosis occurs in specialized tissue called meristematic tissue.
  • Plant meristems occur in growing regions – e.g., root and shoot tips, in cambium of stems and roots.
  • Plants do not have centrioles. Instead they have MTOCs/microtubule organizing centres that perform the same role.
51
Q

Cambium

A
  • tissue layer containing and instrumental in producing meristematic cells (plant version of stem cells, also unspecialized).
  • Located between xylem and phloem
52
Q

Clarification of all those words starting with C but sound the same in this chapter:

A
  • centrioles
  • centromeres
  • centrosomes
  • chromosomes
  • chromatids
  • chromatin
53
Q

Centrioles

A

-structure made from “9+2” microtubule triplets arrangement.
- Centrioles make up centrosomes.
- Centrioles produce spindle fibres that attach to centromere on chromosome.
- These fibres pull the centromere and sister chromatids apart to form daughter chromosomes.

54
Q

Centromeres

A

specialized structures on chromosome appearing during cell division as region holding two sister chromatids together.

55
Q

Centrosomes

A
  • Contains centrioles, animal cells primary microtubule organizing centre.
  • Facilitates organization of spindle poles during mitosis.
56
Q

Chromosomes

A

contains DNA. 23 pairs in each animal cell.

57
Q

Chromatids

A
  • refers to sister chromatids that become daughter chromosomes after being pulled apart.
  • One short arm and one long arm when drawing.
58
Q

Chromatin

A
  • tightly coiled combination of DNA and histone proteins.
  • Made up of nucleosomes.
59
Q

How does the kinetochore work?

A
  • Kinetochores are large proteins assemblies that are present in the centromere of chromosomes and attach to spindle fibres of microtubules.
  • They therefore help in chromosomes segregation during cell division in metaphase and anaphase.
60
Q

How to observe mitosis in prepared slides?

A
  • Onion, garlic and broadbean commonly used for these preparations because their roots grow quickly and the number of chromosomes per cell is low enough to view the individual chromosomes.
  • Slides will generally be sections of root tips. Root tips have meristematic region where mitosis occurs. At end of root tip there is a protective cap – no mitosis takes place there.
  • Root cap cells appear more rounded than meristematic cells (cells undergoing mitosis and differentiating into e.g., xylem or phloem cells).
  • A stain must be used to stain DNA so chromosomes will be visible.

Biology (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions