mitosis

Question 1

what is the name for nuclear division

Answer 1

mitosis

Question 2

what is mitosis

Answer 2

type of nuclear division that maintains the chromosome number; each new daughter cell contains the same genetic information as the parent cell. theyre also genetically identical to each other

Question 3

what does each new cell produced from mitosis have

Answer 3

an exact copy of the DNA present in the parent cell and the same number of chromosomes

Question 4

when is mitosis necessary

Answer 4

when all the daughter cells have to be identical - during growth, replacement and repair of tissues in multicellular organisms

Question 5

what is asexual reproduction

Answer 5

production of genetically identical offspring from one parent in multicellular organisms

Question 6

why do prokaryotic cells divide by binary fission

Answer 6

they have no nucleus so cannot divide by mitosis

Question 7

what does mitosis form

Answer 7

2 new identical daughter cells from original parent cell

Question 8

how many chromosomes are there in diploid organisms

Answer 8

2 copies of each chromosome - 23 pairs

Question 9

what is the diploid number

Answer 9

46

Question 10

what must happen before mitosis can occur

Answer 10

all of the DNA in the nucleus is replicated during interphase. each DNA molecule (chromosome) is converted into two identical DNA molecules called chromatids

Question 11

what is a chromosome

Answer 11

structures in a cell that contain genetic material, also known as DNA.

Question 12

when are chromosomes visible

Answer 12

during cell division.

Question 13

what does each chromosome consist of

Answer 13

two chromatids joined somewhere along its centromere. genetic information along each chromatid is identical

Question 14

what does each chromosome replicate to form

Answer 14

an identical copy (chromatid)

Question 15

what is a chromatid

Answer 15

one of the two identical halves of a chromosome that has been replicated in preparation for cell division. chromatids of a pair are joined at the centromere

Question 16

why is it necessary to keep the chromatids together during mitosis

Answer 16

so they can be manouevred and segregated equally one into each of the daughter cells

Question 17

what does DNA combine with during interphase

Answer 17

proteins called histones to form a dense complex called chromatin

Question 18

what are histones

Answer 18

The proteins that DNA is packaged with. Histones are small spherical structures which the DNA can wind around to make it more compact in the nucleus.

Question 19

what is chromatin

Answer 19

combination of DNA and histones is referred to as chromatin.

Question 20

what is the job of chromatin

Answer 20

to package DNA into a unit capable of fitting within the tight space of a nucleus.

Question 21

what are the four stages of mitosis

Answer 21

-prophase
-metaphase
-anaphase
-telophase
—-> they are described separately but is a continuous process

Question 22

how can we identify each phase of mitosis

Answer 22

under a microscope

Question 23

how can dividing cells be obtained

Answer 23

from growing tips of plants. the root tips can be treated with a chemical to allow cells to be separated. then they are squashed to form a single layer of cells on a microscope slide.

Question 24

how can chromosomes be made more visible

Answer 24

stains that bind to DNA are used

Question 25

how much does mitosis make up the cell cycle

Answer 25

5-10%. its considered to be a separate process to cytokinesis

Question 26

what happens before nuclear division begins

Answer 26

the cell carries out all of its normal functions. DNA synthesis and checking are complete

Question 27

what happens in early prophase

Answer 27

chromsomes become more distinct - they coil up - shorten - thicken - take up stain more intensely - centriole divides - nucleolus becomes less prominent

Question 28

what is the nucleolus

Answer 28

An area inside the nucleus of a cell that is made up of RNA and proteins and is where ribosomes are made.

Question 29

what happens in late prophase

Answer 29

- chromosomes become more distinct and seen to consist of two chromatids joined by a centromere - centrioles migrate to opposite poles of the cell - nucleolus continues to shrink and disappears - nuclear envelope disintegrates

Question 30

what happens in metaphase

Answer 30

- each centriole is at a pole - centrioles grow and produce spindle fibres - spindle fibres attach to the centromere of the chromosomes - each centromere is attached to both poles - chromosomes are pulled to the metaphase plate or equator

Question 31

what happens in anaphase

Answer 31

- spindle fibres contract - centromere divideds - chromatids (daughter chromosomes) are pulled to opposite ends of the cell - centromere is pulled first - each half of the cell receives one chromatid from each chromosome

Question 32

what happens in telophase

Answer 32

- chromosomes reach the poles of the spindle - they begin to uncoil - they become less distinct - nuclear envelope starts to form - when they reach the poles of the spindle the chromatids are now daughter chromosomes

Question 33

what happens after mitosis is complete

Answer 33

cytokinesis - the cell splits into two

Question 34

what happens in cytokinesis

Answer 34

the cell divides the daughter cells have the same chromosome number and genetic makeup as each other and the parent cell - DNA replication precedes mitosis

Question 35

how does cytokinesis occur in animal cells

Answer 35

the plasma membrane folds inwards and 'nips in' the cytoplasm the edges of the cell constricts

Question 36

how does cytokinesis occur in plants cells

Answer 36

an end plate forms where the equator of the spindle was and new plasma membrane and cellulose material are laid down on either side of this end plate

Question 37

what is the goal of cytokinesis

Answer 37

to separate the cell into two distinct daughter cells

Question 38

why are the mechanism for cytokinesis different in plants and animals

Answer 38

due to their structural differences

Question 39

how does a cleavage furrow form

Answer 39

- a cleavage furrow is created using a ring of contractile protein - actin and myosin - the cleavage furrow reaches the center - the cells are pinched apart into two separate daughter cells

Question 40

how do cell plates form in plant cells

Answer 40

- vesicles moved to the equator where they fuse to from tubular structures across the equator - tubular structures merge to form two plasma membranes of the two daughter cells. completion of cell division - pectins and other substances are deposited between the two membranes by exocytosis forming the middle lamella. - cellulose is brought to the middle lamella by exocytosis - cell walls are formed adjacent to the equator

Question 41

compare the mechanism, structure , speed and outcome of cytokinesis in plant and animal cells

Answer 41

mechanism animal - cleavage furrow (contractile ring) plant - cell plate formation (vesicle fusion) structure animal - felxible plasma membrane plant - rigid cell wall speed animal - relatively fast and flexible plant - slower and more complex outcome animal - two daughter cells separated by membrane plant - two daughter cells separated by a new cell wall

Question 42

what is the significance of mitosis

Answer 42

all living organisms need to produce genetically identical daughter cells

Question 43

why is mitosis needed for asexual reproduction

Answer 43

single celled protoctists such as Amoeba and Paramecium divide by mitosis to produce new individuals some plants e.g. strawberry reproduce asexually by forming new plantlets on the ends of stolons (runners) fungi such as single celled yeasts produce asexually by mitosis

Question 44

why is mitosis needed for growth and repair

Answer 44

all multicellular organisms grow by producing more cells that are genetically identical to each other and the parent cell from which they arose by mitosis

Question 45

why is mitosis needed for tissue repair

Answer 45

wounds heal when growth factors are secreted by platelets and macrophages (wbc) and damaged cells of the blood vessel walls, stimulate the proliferation of endothelial and smooth muscle cells to repair damaged blood vessels