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Biology > Cell Cycle > Flashcards

Cell Cycle Flashcards

1
Q

what is cell cycle?

A

series of events from the time a cell is produced until it will produce two daughter cells.

life cycle of a cell

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2
Q

example of cells that divide& do not divide?
cancer is a diesease of ________.

A

divide: skin cells
doesn’t divide: nerve cells
cell cycle

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3
Q

what is asexual reproduction?

A

an organism can produce an offspring that are genetically identical to itself, without the involvement of another organism. No genetic diversity among offspring.

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4
Q

what is sexual reproduction?

A

2 parent organisms, typically a male and a female, contribute specialized reproductive cells (sperm and egg) that fuse together to create genetically diverse offspring.

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5
Q

define chromosome, chromatin, DNA, chromatid, centromere and gene?

A
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6
Q

what is chromosome made up of?

A

DNA & proteins
(histones) which help package and organize the DNA into a compact, functional structure.

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7
Q

what are the phases in interphase?

A

G1phase
S phase
G2 phase
G0 phase

First Gap
Synthesis
Second Gap

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8
Q

what is G1 phase?

A
  1. phase before DNA synthesis
  2. increase protein prduction
  3. grows in size
  4. most organelles duplicate
  5. in end, increased acitivity of enzymes required for DNA synthesis
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9
Q

what is S phase?

A
  1. synthesis phase
  2. DNA synthesis
  3. each chromosome consists of two sister chromatids.
  4. duplication of centrosome.

at the beginning of S phase, the chromosome was single. at the end of S phase, the chromosome duplicates to form a chromosome with 2 sister chromatids.

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10
Q

what is the most important thing that happens in S phase?

A

-After DNA replication , each chromosome consists of two sister chromatids, with each chromatid being a separate DNA molecule.

Before the S phase, each chromosome consists of a single DNA molecule, which is equivalent to a single chromatid.

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11
Q

what happens in G2 phase?

A
  1. increased protein synthesis for production of spindle fibers.
  2. cell prepare itself for M phase
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12
Q

when does G0 phase occur and what happens in this phase?

A

after M phase & before G1 phase
resting phase

the cell is metabolically active

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13
Q

name cells that enter G0 phase permanently or temporarily?

A

In multicellular eukaryotes, cells enter G0 phase from G1 and stop dividing.
Some cells remain in G0 for indefinite period e.g. neurons.
Some cells enter G0 phase temporarily e.g. some cells of liver and kidney.
Many cells do not enter G0 and continue to divide throughout an organism’s life, e.g. epithelial cells.

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14
Q

which cells divide by mitosis and meiosis?

A

somatic (mitosis): cells other than reproductive cells.
germ line (meiosis): sex cells (reproductive cells)

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15
Q

what prevents cell from undergoing mitosis.

A

Inhibition of protein synthesis during G2 phase

inhibition: slowing down or preventing

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16
Q

what is kinetochores?

A

a complex protein structure present at the centromere of chromosome that is the point where spindle fibers attach.

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17
Q

what happens in prophase of mitosis?

A
  1. chromatin condenses into highly ordered structures called chromosomes. with the help of condensation
  2. nuclear membrane & nucleolus disappears.
  3. each pair of the daughter centrosome migrate to the opposite pole of cell.
  4. The “daughter” centrioles start building microtubules by connecting tubulin proteins present in the cytoplasm.

The microtubules formed are called spindle fibres.

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18
Q

Complete set of spindle fibres is known as _________________.
Centrioles undergo duplication during _____________.

A

mitotic spindle
during S phase of the interphase.

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19
Q

how are spindle fiber formed in plants if they don’t have? in which phase?

A

In highly vacuolated plant cells, nucleus has to migrate to the centre of cell before prophase.
The cells of plants lack centrioles. So, spindle fibres are formed by the aggregation of tubulin proteins
on the surface of nuclear envelope during prophase.

the formation of a number of things into a cluster.

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20
Q

what happens in metaphase of mitosis?

A
  1. chromosomes align at the equator forming metaphase plate.
  2. when spindle fibres have grown to sufficient length, some spindle fibres, known as kinetochore fibres, attach with the kinetochores of chromosomes. Two kinetochore fibres from opposite poles attach with each chromosome.
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21
Q

what happens in anaphase of mitosis?

A

The sister chromatids are now sister chromosomes, and they are pulled apart toward the respective centrosomes. The other spindle fibres (non-kinetochore) also elongate.

shortest phase

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22
Q

what is metaphase plate?
Telophase is a reverse of ____________.

A

Chromosomes arrange themselves along the equator of cell forming a metaphase plate.
prophase

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23
Q

what are kinetochore spindle fibers?

A

specialized microtubules that specifically attach to the kinetochore, a protein structure located at the centromere of a chromosome. These microtubules don’t attach themselves; rather, they are actively captured and attached to the kinetochore by molecular interactions.

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24
Q

what happens in telophase of mitosis?

A
  1. A new nuclear envelope forms around each set of separated chromosomes.
  2. nucleolus reappears.
  3. Both sets of chromosomes, now surrounded by new nuclear envelopes, unfold back into chromatin.
  4. spindle fibers disintegrate
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25
Q

how does cytokinesis happen in animal cells?

A

by formation of cleavage furrow
A cleavage furrow develops where the metaphase plate used to be.
The furrow deepens & eventually pinches the parent cell into 2 daughter cells.

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26
Q

how does cytokinesis happen in plant cells?

A

Vesicles derived from the Golgi apparatus move to the middle of cell and fuse to form phragmoplast.
phragmoplast grows outward & fuse with the cell membrane & parental cell wall. The contents of phragmoplast form middle lamella. Each cell forms its primary wall on its side.

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27
Q

what are the cells called which is responsible for the formation of body?
in which phase do the centrioles move to the oppsite poles?

mitosis

A

Somatic cells are those which form the body of organisms
prophase

as they form body so they’re responsible for growth & that’s why mitosis is needed for it.

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28
Q

how does vegetative propagation happen?

A

by mitosis
by means of creeping stems & undeground buds

eg. grasses, sweet potato, strawberry
eg. ginger onion and potato

grasses, sweet potato strawberry

29
Q

what is hydra?

A

tiny multicellular animal
reproduce sexually and asexually
by mitosis by budding

The cells at the surface of hydra undergo mitosis and form a mass called bud. Mitosis continues in the cells of bud and it grows into a new individual.

30
Q

how do these form?

strawberry, onion, sweet potato watermelon, cucumber

A

pg 75

31
Q

how mitosis is important for cell replacement?

A

In some parts of body, e.g. skin and digestive tract, cells are constantly sloughed off and replaced by new ones. New cells are formed by mitosis.
Similarly, red blood cells have short life span (about 4 months) and new red blood cells are formed by mitosis.

32
Q

why is mitosis important?
for development and growth

A

Development and growth
Cell replacement
Regeneration
Asexual reproduction

The number of cells within an organism
increase by mitosis. This is the basis of the
development of a multicellular body from
a single cell i.e. zygote and also the basis of
the growth of multicellular body.

33
Q

what is a tumor?
____ is a means of asexual reproduction.

A

A tumour is an abnormal mass of cells that forms when a group of cells undergo uncontrolled growth and division by mitosis.
mitosis

34
Q

what is malignant and benign tumor?

A

malignant tumours spread to other parts of the body and then form secondary tumours
benign tumor is contained within one area usually in a cell membrane. They always remain at the original site in the body.

benign = bengen = healthy

35
Q

what is metastasis?

A

the spread of cancer cells beyond their original site.

36
Q

what causes a tumor?

A

excessive growth of abnormal cells that divide continuously.

37
Q

what kind of ____________ is not cancerous?
the division
of nucleus is known as __________________.

A

tumor
benign
karyokinesis

malignant tumor is cancerous

38
Q

what is phragmoplast?

A

Vesicles derived from the Golgi apparatus move to the middle of cell and fuse to form a membrane-bounded disc called cell plate or phragmoplast.
The plate grows outward and more vesicles fuse with it. Finally, membranes of cell plate fuse with plasma membrane and its contents join the parental cell wall.

39
Q

diff. b/w mitosis in animal and plant cell?

A

page 75

40
Q

mitosis occurs in ________________ cells of plants.
______ form mitotic appratus in plants?

A

meristematic
spindle fibers

41
Q

what are haploid cells?

A

A haploid cell contains only one complete set of chromosomes.
In humans, the haploid number (n) is 23, meaning that each haploid cell has 23 individual chromosomes.
Haploid cells are typically found in the reproductive organs (e.g., sperm and egg cells) of sexually reproducing organisms. These cells are produced through the process of meiosis, which reduces the chromosome number by half.

42
Q

what are diploid cells?

A
43
Q

the ONLY cells in human body that are haploid are gametes cells. T/F

A

True
the only cells that are haploid are the gametes, which are sperm in males and egg cells (ova) in females.

44
Q

what is zygote?

A

zygote is a diploid cell. It is the result of the fusion of two haploid gamete cells (sperm and egg) during fertilization.

45
Q

what is centromere?

A

two sister chromatids are held together by a structure called the centromere.

46
Q

The term “sister chromatids” is used to describe the two ________ copies of a chromosome that are produced as a result of ______________.

A

identical
DNA replication.

47
Q

in meiosis when does chromatin condense?

A

prophase I
prophase II

48
Q

what are homologous chromosomes?

A

Two chromosomes in a pair normally one inherited from the mother and one from the father is called a homologous chromosome.

49
Q

what is synapsis?

A

The homologous chromosomes pairing length wise with their homologue is called synapsis.
Each pair of synapsed chromosme consist of four chromtids with two centromeres. (tetrad)

50
Q

what is bivalent?

A

Each pair of homologous chromosomes is called bivalent.
Each pair of synapsed chromosme consist of four chromtids with two centromeres. (tetrad)
tetrad is a pair of synapsed chromosomes

51
Q

what is crossing over?

A

Crossing over happens when genetic material is swapped between two non-sister chromatids of homologous chromosomes at the chiasma.

52
Q

chiasmata vs chiasma
what is chiasma?

A

chiasmata= plural
chiasma= singular
The two non-sister chromatids of homologous chromosomes join each other at certain points. These points of attachment are called chiasmata.

53
Q

what happens in prophase I?

A
54
Q

what happens in metaphase I?

A

The pairs of homologous chromosomes align along equatorial plane forming the metaphase plate.
Two kinetochore spindle fibres from the opposite poles attach with a pair of chromosomes.

55
Q

what happens in anaphase I and telophase I?

A

Kinetochore spindle fibres shorten. It results in pulling apart the chromosomes of each pair. Each chromosome still contains a pair of sister chromatids.

Spindle network disappears, and nuclear envelope is formed around each haploid set. Chromosomes uncoil back into chromatin. Nuceloli reappear.

56
Q

interphase II?

A

The interphase II is different from the interphase of mitosis and meiosis I. There is no S-phase and is very brief. No DNA replication.

After meiosis I both haploid daughter cells enter a period of rest known as interkinesis/interphase II.

57
Q

explain meiosis II?

A

Prophase II takes much less time compared to prophase I. In this prophase, nucleoli and nuclear envelope disappear and chromatin condenses. Centrioles move to the polar regions and make spindle fibres.
In metaphase II, chromosomes attach with kinetochore spindle fibers and align at
the equator of cell.
This is followed by anaphase II, where centromeres are cleaved and sister chromatids are pulled apart. The sister chromatids are now called sister chromosomes, and they are pulled toward
opposing poles. Telophase II is marked with uncoiling of chromosomes into chromatin. Nuclear envelopes reform; cleavage or cell wall formation eventually produces a total of 4 daughter cells, each with a haploid set of chromosomes

58
Q

what is the significance of meiosis?

A

meiosis is necessary not only to maintain the chromosome no. in the next generation but also to produce variations in next generation.

59
Q

how meiosis provides variations in next generations?

A

the chromosomes undergo crossing over. the daughter cells have genetic variations. When gametes fuse to form zygote, it (zygote) is genetically different from both parents.

daughter cells= gametes (sperm & egg)

60
Q

what kind of error occur in meiosis?

A

non-disjunction
Nondisjunction is the failure of the chromosomes to separate, which produces daughter cells with abnormal numbers of chromosomes.

If such abnormal gamete fuses with a normal gamete,
it results abnormal chromosome number in next generation.
for example 47 or 45 chromosomes in humans.

61
Q

what is disjunction?

A

During anaphase I, chromosomes separate and go to opposite poles while during anaphase II sister chromatids separate.

62
Q

comparison b/w meiosis & mitosis with diagram?

A

pg. 129

eLearn.Punjab

63
Q

what is necrosis and apoptosis?

A

two ways/patterns in which cell undergoes death.

64
Q

what is necrosis?
causes of necrosis?
effects of necrosis?
what if left untreated?
example?

A

cause: disease, injury/ failure of blood supply.
severe swelling, break down of cell organelles causes inflammation by releasing toxins

65
Q

what is apoptosis?
causes of apoptosis?
effects of apoptosis?

A

programmed cell death. Many cells proceed to self-destruction when they have completed prescribed function. The cell death by self-desturction is called apoptosis.
Apoptosis can occur when a cell is damaged or undergoes stress conditions. Apoptosis removes the damaged cell

66
Q

Cell membrane makes irregular ________ known as _______. __________ break off from the cell and are now called _________, which are then ________ by other cells.

A

buds
blebs
blebs
apoptotic bodies
phagocytosed

why phagocytosed??

67
Q

what are apoptotic bodies?
phagocytosis of apoptotic bodies takes place by _______.

A

Cell membrane makes irregular buds known as blebs. Blebs break off from the cell & are now called apoptotic bodies
WBCs

68
Q

examples of apoptosis?

A

page 79
when cells are damaged by disease.
in aging.
the growth of the cells b/w fingers that are no longer needed, undergo apoptosis

Biology (9 decks)

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