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Biology > 1.6 > Flashcards

1.6 Flashcards

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1
Q

What are the three main stages of the cell cycle

A

Interphase

Mitosis

Cytokinesis

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2
Q

What is the longest stage of the cell cycle

A

Interphase

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3
Q

What stages take place in interphase

A

G1 phase

S phase - DNA replication

G2 phase

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4
Q

Where do all the stages in interphase take place

A

G1 - cytoplasm
S - nucleus
G2 - cytoplasm

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5
Q

What takes place in G1 (Gap 1)

A

the cell grows and functions normally

rapid protein synthesis takes place, cell grows in size

proteins required for DNA synthesis are made

Mitochondria and chloroplasts are replicated

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6
Q

What takes place in the S phase

A

DNA doubles

DNA replication takes place

Genetic material is duplicated, no chromosomes form

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7
Q

What takes place in G2

A

Protein synthesis occurs to produce proteins needed for cell division such as microtubule proteins that make up a mitotic spindle

cell is preparing for cell division

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8
Q

What is mitosis

A

the division of the nucleus into two genetically identical daughter nuclei

involves separation of sister chromatids into individual chromosomes which are then distributed among the daughter nuclei.

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9
Q

What is cytokinesis

A

once mitosis has ended, the cytoplasm go a parental cell is divided between the two daughter cells

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10
Q

What are cyclins

A

cyclins are a family of proteins that control the progression of cells through the cell cycle

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11
Q

what happens unless thee are no cyclins

A

cells cannot progress to the next stage of the cell cycle unless the specific cyclin reaches a certain concentration

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12
Q

what do cyclins bind to

A

enzymes called cyclin dependent kinases (CDKs) and activate them

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13
Q

what do cyclin dependent kinases do once activated

A

they activate CDKs then attach phosphate groups (phosphorylation) to other proteins in the cell.

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14
Q

what does the attatchment of phosphate trigger

A

other proteins to become active and carry out tasks

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15
Q

What happens if mutations occur on genes for the cyclins

A

problems in regulating the cell cycle may happen which may lead to cancer

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16
Q

What cyclin controls the G1 phase

A

Cyclin D - gradually increases

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17
Q

what cyclin controls the S phase

A

Cyclin E - for DNA replication and promotes centromere duplication

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18
Q

What cyclin controls the G2 phase

A

Cyclin A - for DNA replication

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19
Q

what cyclin controls mitosis

A

Cyclin B - formation of mitotic spindles and the alignment of chromatids

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20
Q

acronym for cyclins

A

DEAB

G1 - s phase - G2 - mitosis

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21
Q

what are histones

A

basic proteins (alkaline) that form part of the nucleosome. DNA is tightly wound around them

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22
Q

how is DNA present in interphase

A

as Chromatin

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23
Q

How is DNA presented in prophase

A

DNA supercoils and becomes visible as a pair of sister chromatids that are identical to each other connected by centromeres

24
Q

how is DNA referred to during anaphase

A

they are chromosomes

25
Q

what happens in prophase

A

DNA supercoils causing the chromatin to condense.
Nucleolus disappears.
Nuclear membrane disintegrates.
Spindle fibres (made of microtubules) start to form (and are completely formed by the end of prophase).
Centrioles (absent from plant cells) move to opposite poles.

26
Q

what happens in metaphase

A

Spindle fibres bind to the centromere of sister chromatids and cause their movement towards the equatorial plate.
Sister chromatids are aligned at the equatorial plate at the end of metaphase.

27
Q

what happens in anaphase

A

Sister chromatids are separated (now known as chromosomes) and pulled to opposite poles by the spindle fibres.

28
Q

telophase

A

The chromosomes have reached the poles.
A nuclear membrane starts to reform at each pole.
A nucleolus appears in each new nucleus.
The spindle fibres disintegrate.
The cell elongates in preparation for cytokinesis.
In some cases, the invagination of the membrane is also visible (marking the beginning of cytokinesis).

29
Q

What is the mitotic index

A

the ratio of the number of cells in a population undergoing mitosis to the total number of visible cells

30
Q

what is the mitotic Index equation

A

p + M + A + T / total cells

31
Q

what happens to the mitotic index in a tissue where cell division is uncontrolled

A

mitotic index is higher than in the normal tissue

32
Q

what is cytokinesis

A

the division of the parental cytoplasm between two daughter cells after mitosis

33
Q

what happens in cytokinesis in animal cells

A

A ring of protein (microfilaments) located immediately beneath the plasma membrane at the equator pulls the plasma membrane inward.

The inward pull on the plasma membrane produces the characteristic cleavage furrow.

When the cleavage furrow reaches the centre of the cells, it is pinched apart to form two daughter cells.

34
Q

wha happens in cytokinesis in plant cells

A

In plants Golgi apparatus forms vesicles that consist of material to build a new cell wall. Vesicles merge and form the cell plate. The cell plate grows and divides into two daughter cells.

35
Q

what is a benign tumour

A

a localised tumor, that does not spread to other parts of the body

36
Q

what is a malignant tumour

A

ca cancerous growth that is often resistant to treatment

37
Q

what is tumorigenesis

A

the formation of a tumour

38
Q

what is a tumour

A

a mass of cells that divide uncontrollably

39
Q

what are the two types of tumors

A

benign and malignant

40
Q

which tumour causes cancer

A

malignant

41
Q

what can cause tumors

A

mutations - specifically in the cyclins

42
Q

what is a mutation

A

a change in an organisms genetic code

a change in the base sequence of a certain gene that can result in tumour formation

43
Q

what do mutations not aways cause

A

they do not always cause tumors

44
Q

what are mutagens

A

agents that cause gene mutations

45
Q

examples of mutagens

A

chemicals - carcinogens

high energy radiation

short wave ultraviolet light

grays

some viruses

46
Q

what is an oncogene

A

a gene that has undergone a mutation and contributes to the development o ftumours

47
Q

what are proto-oncogenes

A

oncogenes that have not mutated and assist in the regulation of cell division

48
Q

what is metastasis

A

the movement of cells from a primary tumour to other parts of the body where they develop into secondary tumors

49
Q

what are the steps to forming a secondary tumor

A

cancerous cells detach from the primary tumor

cancerous cells gain the ability to penetrate the walls of lymph or blood vessels and so circulate around the body

the circulating cancerous cells invade tissues at different lotions and develop by uncontrolled cell division into secondary tumors

50
Q

What can smoking tobacco lead to

A

stroke, cancers and asthma

51
Q

A cell that is dividing too rapidly may have lost its ability to enter which part of the cell cycle?

A

G1 phase

52
Q

What is a difference between a cell in G1 phase and a cell in G2 phase of the cell cycle

A

A cell in G2 has more mitochondria than a cell in G1 and it would also be slightly larger as it has duplicated its DNA

53
Q

What cyclin increases to trigger the beginning of mitosis

A

cyclin B

54
Q

Discuss possible exceptions to the cell theory (4 marks)

A

Striated muscle cell - multi nucleated, large in size
Aseptate fungal hyphae - multi nucleated, no dividing cell walls at times

why they challenge the theory

55
Q

Outline the processes that occur in a cell during interphase, including those needed to prepare for mitosis. 4 marks

A 
S phase - DNA replication 
DNA transcription takes place 
Enzyme and protein synthesis 
Cell respriation 
Growth 
Organelles replication

Biology (51 decks)

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