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Biology > cell division, cell diversity and cell differentiation 2.6 > Flashcards

cell division, cell diversity and cell differentiation 2.6 Flashcards

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1
Q

what are the two phases of the cell cycle?

A

-the M phase and interphase

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2
Q

describe what happens at the G1 phase?

A

preparation for DNA replication. MRNA’s and proteins required are synthesised (transcription/ translation) =protein synthesis
-growth of cells
- growth of organelles
- increase in number of organellles

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3
Q

what happens at the S phase

A
  • DNA replication
    -sister chromatids are produced
    -must occur so that the daughters cells have identical DNA
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4
Q

what happens at the G2 phase?

A

-growth of organelles
-increase in number of organelles
-protein synthesis
-spindle fibres begin to form

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5
Q

what two stages are in the mitotic stage?

A
  • mitosis
    -cytokinesis
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6
Q

what is the difference between mitosis and cytokinesis?

A

-in mitosis the chromosomes separate into two nuclei and in cytokinesis the cell divides into two

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7
Q

what are the reasons for cells entering the G0 phases?

A
  • they are fully differentiated
    -repair the DNA
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8
Q

how do we know the cell is in interphase by looking into a microscope?

A
  • the chromosomes are not visible so a dark material called chromatin is seen
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9
Q

What is the difference in the M phase of a plant cell ?

A
  • plants cells don’t have centrioles so they do not play a role in the forming the spindle apparatus
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10
Q

describe what happens in prophase of mitosis

A
  • chromosomes condenses and becomes visible
  • nuclear envelope break down
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11
Q

describe what happens in anaphase of mitosis

A
  • sister chromatids are pulled to opposite poles of the cell by the spindle fibres contrcting
  • centromere breaks
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12
Q

describe what happens in metaphase of mitosis

A

-chromosomes line up along the equator of the cell
-spindle fibres attach on the centromere on the chromosomes

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13
Q

describe what happens at telophase in mitosis

A

-Nuclear envelope begins to form;
-Chromosomes uncoil;
-spindle fibres breaks down

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14
Q

How is the cell cycle regulation?

A

after each process there are checkpoints to ensure there is no damage

During G1 phase – chromosomes are checked for damage. If damage is detected then the cell does not advance into the S phase until repairs have been made
During S phase – chromosomes are checked to ensure they have been replicated. If all the chromosomes haven’t been successfully replicated then the cell cycle stops
During G2 phase – check for a mutation in the DNA,Daugther cells might not receive identical genetic information
During metaphase – the final check determines whether the chromosomes are correctly attached to the spindle fibres

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15
Q

What is the significance of mitosis in life cycles

A

-asexual reproduction
-repair of damage tissue/cells
-growth of an organism

in plants,animal and fungi

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16
Q

describe the stages in meiosis 1

A
  • prophase 1- chromosomes condense and become visible
  • homologous chromosomes link together forming chiasmata (bivalent)
  • crossing-over
  • nuclear membrane breaks down
  • spindle fibres start to form

metaphase 1 -Bivalents line up on equator of cell
-Independent assortment

anaphase 1-homologous pairs are separated by the spindle fibre and pulled to opposite poles.
- chiasmata between homologous chromosomes but the centromeres are still attached so they are no longer bivalent

telophase 1
- nuclear membrane reforms
- chromosomes uncoil

17
Q

describe the stages in meiosis 2

A
  • same processes as in one however instead of bivalent chromosomes they just normal( similar to mitosis)
    -crossing over also does not take place in prophase two as there are no bivalent pairs
    -independent assortment occurs in metaphase 2
18
Q

why is meiosis known as reduction division?

A
  • because the chromosomes number halves
19
Q

ways in which variation takes place in meiosis

A
  • crossing over- pairs of chromatids are broken off and exchanged between homologous chromosomes. which exchange alleles (recombinant chromosomes)
  • independent assortment- arrangement of homologous chromosomes along the spindle apparatus
  • random fusion of gametes - random fusion of gametes at fertilization creates genetic variation between zygotes as each will have a unique combination of alleles
20
Q

the significance of meiosis in life cycles

A
  • increases genetic variation
  • production of haploid cells
21
Q

erythrocyte’s (red blood cells)

A

-They are biconcave in shape which increases the surface area over which oxygen can be absorbed
-The cytoplasm contains high amounts of the pigment haemoglobin which can readily bind to oxygen
-No nucleus is present which makes more space inside the cell for haemoglobin molecules for maximum oxygen-carrying capacity

22
Q

neutrophils

A
  • They are flexible which enables them to engulf microorganisms
  • There is a large number of lysosomes present in the cell. These digestive enzymes help to digest and destroy invading cells
    -they have a lobed nucleus
23
Q

spermatozoa (sperm cells)

A

-many mitrochondria to provide energy for movement
-acrosomes which contain digestive enzymes that allow the sperm cell to penetrate the surface of the egg cell
-flagellum for movement

24
Q

palisade cells

A

Adaptations:
- A large number of chloroplasts (the site of photosynthesis) are present in the cytoplasm to maximise the absorption of photons for photosynthesis
-thin allow light to penatrate through

25
Q

guard cells

A
  • Function: control the opening of the stomata to regulate water loss and gas exchange
  • become turgid and flaccid
26
Q

tissue

A

Tissues are the same type of cell working together for the same function

27
Q

root hair cell

A

-increased surface are to volume ratio for uptake of water and minerals
-thin walls to allow effecient exchange

28
Q

organs

A

a group of differnt tissues working for the same function

29
Q

organ system

A
  • made up of organs
30
Q

what are stem cells

A

-undifferentiated cells that can differentiate into any cell type by mitosis

31
Q

totipotent stem cellls

A

-can differntiate into any tpe of body cell and also extra-embryonic cells
-early embroyonic cells

32
Q

pluripotent stem cells

A

-can differntiate into any type of bosy cells but can not form extra-embryonic cells
-embroyonic stem cells

33
Q

multipotent stem cells

A
  • can only diferentiate into some body cells
  • adult stem cells found in bone marrow
34
Q

potential uses of stem cells

A

-to treat alziemers and parkminsons

35
Q

Squamous epithelial cell

A

-very thin to provide a short diffusion distance for gases

Biology (26 decks)

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