cell division

Question 1

Cell division

Answer 1

nuclear division (meiosis and mitosis) and cytoplasmic division (cytokenesis) must occur

Question 2

Interphase

Answer 2

stage between cell divisions
G1 phase (growth phase)
Duplication of the chromosome (DNA replication)
duplication of centromeres (S phase - synthesis phase)
G2 phase (growth phase)
G0 (sometimes)
Chromosomes not visible

Question 3

Growth phase

Answer 3

growth and reproduction of organelles as cell prepares to divide

Question 4

G0

Answer 4

Undergoing an extended G1 phase but are not preparing to replicate their DNA and divide.
cells in stage are withdrawn from active cell cycle and can only re-enter under some circumstances

Question 5

centromere

Answer 5

Contains 2 centrioles
becomes visible in S phase
Produces spindle fibre

Question 6

S phase

Answer 6

Chromatin duplicates and the cell doubles its amount of genetic material

Question 7

cytokenesis

Answer 7

Occurs after mitosis
forms two seperate diploid daughter cells
Division and separation of the cytoplasm to create the new daughter cells

Question 8

Mitosis

Answer 8

Interphase
prophase
Metaphase
anaphase
Telophase

Question 9

prophase (Mitosis)

Answer 9

Chromatid threads condense to form chromosomes
nuclear membrane disintegrate and nucleotides disappears
Spindle fibre forms and attaches to each chromosome at centromere
centromeres move towards opposite poles of the cell

Question 10

Metaphase (Mitosis)

Answer 10

Chromosomes move to centre of the cell and live up along the equator of the cell. Equator referred to as the metaphase plate.
centromeres of chromosomes are aligned on the equator
The centrioles are located at opposite poles of the cell

Question 11

Anaphase (mitosis)

Answer 11

Spindle microtubules shorten and pull on the centromeres
spindle microtubules pull sister chromatids pull to opposite poles of the cell
Sister chromatids now referred to as chromosomes
at the end of phase, each pole has complete identical set of maternal and paternal chromosomes

Question 12

Telophase (mitosis)

Answer 12

chromosome decompress to form chromatin, no longer visible under microscope
Two new nuclear membranes form for each cell
Nucleoli reappear, spindle fibre apparatus disappears.
Cell elongates and cleavage furrow forms to become ready for cytokinesis

Question 13

cytokinesis in plants

Answer 13

Cytoplasm of plant cells divide with the formation of a structure called a cell plate.
cell plate - formed when parts of cell wall fuse wt spindle fibre, cellulose is deposited there, forming a wall that divides the parent cell.

Question 14

Cytokinesis in animals

Answer 14

cytoplasm divides by process known as cleavage.
Cell membrane around the middle of the cell draws together to form a cleavage furrow.
cleavage furrow continues to develop until the cell membrane eventually meets at a point, cell then splits

Question 15

Binary fission

Answer 15

reproduction of prokaryotes as they lack nucleus.
Process of asexual reproduction whereby a prokaryotic cell divides into two identical daughter cells.
process includes: DNA replication, chromosome segregation, cytokinesis
Mutation is only cause of variation in prokaryotes. Process much quicker compared to meiosis and mitosis, therefore higher rates of mutation.

Question 16

binary fission steps

Answer 16

Prokaryote replicates their single DNA strand, signalling beginning of binary fission.
original and replicate chromosomes attach to the cell membrane and are pulled to seperate poles as the cell elongates.
Cleavage furrow develops forming new cell wall.
New cell wall fully develops
two cells seperate (cytokinesis), chromosomes become tightly coiled again.
Continuous process.

Question 17

meiosis

Answer 17

Production of gametes
plants - gametes are pollen and ovules
Daughter cells have half of parent cell DNA
two divisions of nucleus take place - 1 DNA replication
Called a reduction division
Bivalent - during Meiosis 1, homologous chromosomes pair and physically connect. Synapsis is what causes them to physically connect.

Question 18

Crossing over

Answer 18

exchange of genetic material between maternal and paternal homologous chromosomes

Question 19

Recombination of genes

Answer 19

happens through: crossing over, independent assortment and random fertilisation

Question 20

Random assortment

Answer 20

independent assortment
Assortment of one pair of chromosomes between daughter cells is independent of that of another pair.

Question 21

Meiosis

Answer 21

Prophase 1
Metaphase 1
Telophase 1
Cytokinesis 1
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2
Cytokinesis 2

Question 22

Prophase 1

Answer 22

Chromatin condenses forming chromosomes
crossing over occurs
Nuclear membrane disintegrates and nucleolus disappears
spindle fibre attaches to chromosomes at centromere.
Centromeres move to opposite poles

Question 23

Metaphase 1

Answer 23

Chromosomes line up along metaphase plate (equator) in pairs
lining up of chromosomes at equator is independent assortment

Question 24

Anaphase 1

Answer 24

Spindle fibres shorten, pulling on centromere of each chromosome.
one of each pair moves to each end of the cell

Question 25

Telophase 1

Answer 25

new nuclear membranes form and the chromosomes uncoil
Spindle fibres disintegrate

Question 26

cytokinesis 1

Answer 26

Separation of cytoplasm
now 2 cells

Question 27

Prophase 2

Answer 27

Chromosomes visible
spindle fibre produced
Nuclear membrane disintegrates

Question 28

Metaphase 2

Answer 28

Individual chromosomes line up single file along the equator in random order
spindle fibres attach to sister chromatids at the centromeres

Question 29

Anaphase 2

Answer 29

Centromeres of each chromosome disconnect, allowing the sister chromatids to seperate
spindle fibres shorten and individual sister chromatids move to opposite poles of the cell.
In animal cells, cell membrane pinches inwards to form a cleavage, whereas in plant cells new cell wall plates form.

Question 30

Telophase 2

Answer 30

Chromosomes unwind, loosen and reform chromatin
four new nuclear membranes form around the nuclei, one in each new daughter cell

Question 31

Cytokinesis 2

Answer 31

separation of cytoplasm
Now 4 genetically unique cells (4 haploid daughter cells)