Cell Division, Cell Diversity and Cell Organisation

Question 1

What happens in the G1 phase of the cell cycle?

Answer 1

-Organelle replication
-Cell increases in volume
-Protein synthesis

Question 2

What happens at the G1 checkpoint of the cell cycle?

Answer 2

-Checks for DNA damage
-Checks cell is large enough
-Checks cell has duplicated organelles

Question 3

What happens in the S phase of the cell cycle?

Answer 3

-Ensures there is twice the original DNA content (each daughter cell will receive half)

Question 4

What happens in the G2 phase of the cell cycle?

Answer 4

-Cell increases in volume
-Energy stores increase
-Key proteins synthesised for cell division

Question 5

What happens at the G2/S checkpoint of the cell cycle?

Answer 5

-Checking for correct DNA replication

Question 6

What happens at the M (metaphase) checkpoint of the cell cycle?

Answer 6

-Checks spindle fibres are correctly attached to chromosomes

Question 7

What does it mean if a cell is in resting phase?

Answer 7

-Cells are not actively dividing

Question 8

What is the order of stages in mitosis?

Answer 8

1. Prophase
2. Metaphase
   (metaphase checkpoint)
3. Anaphase
4. Telophase

Question 9

What happens during prophase in mitosis?

Answer 9

-Chromatin condenses- chromosomes become visible (form X shape)
-Nuclear envelope breaks down
-Nucleolus disappears
-Centrioles migrate to opposite poles of the cell
-Spindle fibres start to form

Question 10

What happens during metaphase in mitosis?

Answer 10

-Spindle fibres attach to centromeres of each pair of sister chromatids
-Chromosomes line up along the equator of the cell

Question 11

What happens during anaphase in mitosis?

Answer 11

-Spindle fibres shorted and pull sister chromatids apart and separate them to opposite poles of the cell
-Centromere has divided

Question 12

What happens during telophase in mitosis?

Answer 12

-There is now a full set of chromosomes at each pole of the cell
-Nuclear membrane forms around each set of chromosomes
-Nucleolus reappears
-Chromosomes uncoil and reforms chromatin

Question 13

What are the stages of cytokinesis in animal cells

Answer 13

-Cleavage furrow forms down the centre of the cell
-Actin microfilaments contract (requires ATP)
-Cell separates by pinching the plasma membranes together
-Forms two genetically identical daughter cells

Question 14

What are the stages of cytokinesis in plant cells?

Answer 14

-Vesicles containing cellulose are deposited at cell plate
-Cellulose molecules hydrogen bond together
-Forms two genetically identical daughter cells
(plants do not contain centrioles)

Question 15

What is a stem cell?

Answer 15

An unspecialised, self renewing cell that has potential to turn into most cells, including another stem cell

Question 16

What are the different types of stem cell?

Answer 16

-Totipotent stem cell (embryonic)
-Pluripotent stem cells (embryonic)
-Multipotent stem cells (somatic / adult)
-Induced pluripotent stem cells

Question 17

What are totipotent stem cells?

Answer 17

-They are extracted from the first 1-32 cells of an embryo
-They can differentiate into ALL cell types
-This has the ability to form whole living organisms

Question 18

What are pluripotent stem cells?

Answer 18

-Extracted from the first 64-256 cells of an embryo
-Can differentiate into all cell types, EXCEPT placenta and umbilical chord cells

Question 19

What are multipotent stem cells?

Answer 19

-Found in bone marrow
-Can differentiate into many cell types, including lymphocytes, ect.

Question 20

What are Pluripotent stem cells?

Answer 20

-They reprogram differentiated cells to become embryonic/ pluripotent stem cells
-These have potential in areas like regenerative medicine

Question 21

What are the stages of Meiosis 1?

Answer 21

-Prophase 1
-Crossing over
-Metaphase 1
-Independent assortment
-Anaphase 1
-Telophase 1

Question 22

What happens in prophase 1 in meiosis 1?

Answer 22

-Chromatin condenses and chromosomes become visible
-Nuclear envelope breaks down and nucleolus disappears
-Spindle fibres start to form

Question 23

What happens in the crossing over stage 1 in meiosis 1?

Answer 23

-Non sister chromatids within the same homologous pair exchange short sections of DNA
-This forms a new collection of alleles

Question 24

What happens in metaphase 1 in meiosis 1?

Answer 24

-Each homologous pair lines up along the equator
-Spindle fibres attach to centromeres

Question 25

What is the independent assortment phase in meiosis 1?

Answer 25

-The orientation of each homologous pair along the equator is random (increases variation)

Question 26

What happens in anaphase 1 in meiosis 1?

Answer 26

-Spindle fibres shorten and separate each member of a homologous pair to opposite poles
-The centromere remains intact

Question 27

What happens in telophase 1 in meiosis 1?

Answer 27

-Nuclear envelope reforms and nucleolus reappears

Question 28

What happens prior to meiosis 2?

Answer 28

There is a short cell cycle without DNA replication

Question 29

What happens in Prophase 2 of meiosis 2?

Answer 29

-Chromatin condenses and chromosomes become visible
-Nuclear envelope breaks down
-Nucleolus disappears
-Spindle fibres start to form

Question 30

What happens in metaphase 2 of meiosis 2?

Answer 30

-Chromosomes line up along the equator
-Spindle fibres attach to centromeres

Question 31

What is independent assortment in meiosis 2?

Answer 31

-Variation in metaphase 2 - there is a random orientation of chromosomes along the equator which determines which daughter cell each sister chromatid is separated to

Question 32

What happens in anaphase 2 of meiosis 2?

Answer 32

-Spindle fibres shorten
-Centromere divides
-Sister chromatids pulled to opposite poles

Question 33

What happens in telophase 2 of meiosis 2?

Answer 33

-Nuclear membrane forms around each set of chromatids at each pole
-Nucleolus reappears
-Chromatids relax to reform chromatin