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1. Cell Biology > Cell division > Flashcards

Cell division Flashcards

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1
Q

What are the three main stages on the cell cycle?

A
  • Interphase, Mitosis, Cytokinesis
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2
Q

What is the interphase?

A
  • First stage, the most active and longest phase of the cell cycle
  • It involves many processes that occur both in the nucleus and cytoplasm
  • With in this stage there are three stages: the G1 (Gap 1), S (synthesis), and G2 (Gap 2 )
  • DNA exists as chromatin
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3
Q

What processes are involved in interphase?

A

The processes include (DOCTOR):
- DNA replication (during the S phase) and RNA synthesis
- Organelle duplication (twin daughter cells)
- Cell growth (size must increase before division)
- Transcription/translation (synthesis of proteins)
- Obtain nutrients (cellular materials)
- Respiration (ATP production

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4
Q

Explain where and what happens in the G1 phase of the interphase.

A
  • In the cytoplasm
  • Rapid protein synthesis, cells increases in size
  • The proteins that are required for DNA synthesis (the next phase) are made
  • Mitochondria and chloroplasts (in plants) are replicated
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5
Q

Explain where and what happens in the S phase of the interphase.

A
  • In the nucleus
  • The amount of DNA doubles as DNA replication takes place
  • Genetic material in the form of chromosomes are duplicated
  • Mitochondria and chloroplasts (in plants) continue to be replicated
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6
Q

Explain where and what happens in the G2 phase of the interphase.

A
  • In the cytoplasm
  • Protein synthesis occurs to produce the proteins needed for cell division, such as microtubule proteins that will make up a mitotic spindle
  • The cell has more mitochondria than the cell in the G1 phase
  • The cell prepares for cell division
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7
Q

When a cell is dividing too rapidly may have lost the ability to enter which phase?

A

G1 phase

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8
Q

What are cyclins?

A
  • Cyclins are a family of proteins that control the progression of cells though the cell cycle
  • The cyclin needs to reach a certain concentration so that the cell can progress to the next stage
  • Cyclins bind to enzymes called cyclin-dependent kinases (CDKs) which are activated
  • In order to activate proteins, the CDKs attach a phosphate group to the proteins
  • The CDKs attach phosphate groups to other proteins in the cell, which causes the proteins to become active and carry out tasks
  • Cyclins and CDKs regulate the cell cycle, the speed can be controlled and the cycle can be stopped completely
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9
Q

What type of cyclins have an effect on which stage in the interphase stages and in mitosis?

A
  • In the G1 phase, the cyclin D levels gradually increase
  • In the S phase, the cyclin E is important for DNA replication and also promotes centromere duplication
  • In the G2 phase, the cyclin A helps promote DNA replication
  • In Mitosis, the cyclin B helps in the formation of mitotic spindles and the alignment of chromatids
  • Order: D, E, A, B
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10
Q

What is mitosis?

A
  • The division of the nucleus into two genetically identical daughter nuclei
  • The sister chromatids are separated into individual chromosomes which are then distributed among the daughter nuclei
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11
Q

What factors are involved in mitosis? What are histones and chromatin?

A
  • The DNA which was replicated in the S phase is used
  • In eukaryotic cells, DNA replication requires chromosomes, the DNA is tightly wound around proteins called histones
  • Histones: are alkaline proteins that form part of nucleosomes, which are coiled together in a specific pattern to form a chromosome
  • The DNA that is packed by histones, forms chromatin which undergo condensation to form the chromosomes
  • Chromatin is a lower order of DNA organization
  • The order of DNA organization changes throughout the stages of mitosis
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12
Q

What are the four phases of mitosis?

A
  • Prophase, Metaphase, Anaphase, Telophase

Diagrams of each phase in book. Be able to identify these stages on a micrograph.

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13
Q

What happens in the prophase? Give 6 details.

A
  • DNA supercoils causing the chromatin to condense
  • The nucleolus disappears
  • Nuclear membrane breaks up
  • Spindle fibers (made of microtubules) form
  • Centrioles (only present in animals) move to opposite poles
  • DNA exists as a pair of sister chromatids that are identical to each other
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14
Q

What happens in metaphase?

A
  • Spindle fibers bind to the centromere of sister chromatides and cause their movement towards the equatorial plate
  • Sister chromatides are aligned at the equatorial plate at the end of the phase
  • DNA present as Sister chromatides
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15
Q

What happens in anaphase?

A
  • Shortest phase of mitosis
  • Sister chromatides are separated and pulled to opposite poles by the spindle fibers
  • DNA present in the form of chromosomes
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16
Q

What happens in telophase?

A
  • The chromosomes have reached the poles
  • A nuclear membrane starts to form at each pole
  • A nucleolus appears in each new nucleus
  • The spindle fibers disintegrate (break up)
  • The cell elongates in preparation for cytokinesis
  • DNA is present as chromosomes
17
Q

How do you calculate the mitotic index?

A
  • The ratio= the number of cells in a population undergoing mitosis (all phases): to the total number of visible cells
  • mitotic index= P+M+A+T/Total cells
  • Important to know because in a tumor the mitotic index is higher than in normal tissue.
  • The index predicts how quickly a cancer could spread
18
Q

What is cytokinesis?

A
  • The cytoplasm of a parental cell is divided between the two daughter cells
  • This process occurs after mitosis and often starts in telophase
  • It is different for animals and plant cells due to the presence of a cell wall in plant cells
19
Q

What are the differences between animal and plants cells during cytokinesis?

A

Animal
- Microfilaments (rings of proteins), which are beneath the plasma membrane at the equator, pull the plasma membrane inward
- This inward pull produces a cleavage furrow
- When the cleavage furrow reaches the center of the cell it is pinched apart to form two daughter cells
Plants
- In the Golgi apparatus, vesicles form that consist of material to build a cell plate
- The vesicles merge and form a new cell wall, which grows and divides into two daughter cells

Diagrams in book

20
Q

What is tumorigenesis?

A
  • The formation of a tumor (or multiple) which is defined as a mass of cells that divide uncontrollably
  • The 2 types of tumors: benign and malignant tumors
  • Cancer is caused by malignant tumour
21
Q

What is a benign tumor and what is a malignant tumor?

A
  • Usually localized and does not spread to other parts of the body, they respond well to treatment
  • A cancerous growth that is often resistant to treatment and may spread to other parts of the body and may recur after being removed.
22
Q

What causes tumors?

A
  • When the cell cycle is disrupted because of a mutation in one of the cyclins, CDKs or a protein associated with the cell cycle
  • Over 50% of all tumors have a mutation in the p53 gene
  • The cells loses its ability to enter the G1 phase and continues to divide rapidly, uncontrolled growth
  • Cancer can occur is any organ or cell
23
Q

What are mutations, mutagens and oncogene?

A
  • Mutations: a change in an organism’s genetic code (base sequence) may lead to a tumor
  • Not all gene mutations lead to uncontrolled cell division
  • Anything that causes a mutation has the potential to cause a cancer
  • Mutagens: agents that cause gene mutation
  • E.g. chemicals that are carcinogens such as dioxin, high-energy radiation (x-rays), short wave ultraviolet light, some viruses (hepatitis B)
  • Oncogene: a mutated gene that contributes to the development of a tumor. When not mutated they are called proto-oncogenes
24
Q

How do primary tumors develop into secondary tumors?

A
  • Cancerous cells detach from the primary tumor and may end up in the blood circulation which may lead them to invade tissues at different locations and develop into secondary
  • The development occurs due to uncontrolled cell division. The tumor has metastasized.
  • Metastasis: movement of cells from primary tumor to other parts of the body where they develop into secondary tumors
25
Q

What is the correlation between smoking and cancer?

A
  • Smoking causes lung cancer and other types of cancers and other diseases (asthma, stroke)
  • There is a strong correlation between smoking and the incidence of cancer
  • It is positive correlation and not causation
  • Increasing consumption of cigarettes and the number of years a person smokes increase the risk of developing lung cancer

1. Cell Biology (6 decks)

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