Cell Division

Question 1

what is the cell cycle and its stages

Answer 1

regulated cycle of division and intermediate growth periods
interphase
mitosis/meiosis
cytokinesis

Question 2

outline what happens during interphase

Answer 2

G1-synthesises proteins for replication and cell size doubles
S-DNA replicates
G2- organelles divide

Question 3

what is the purpose of mitosis

Answer 3

produce two genetically identical daughter cells
growth
cell replacement
asexual reproduction

Question 4

name the stages of mitosis

Answer 4

Prophase
Metaphase
Anaphase
Telophase

Question 5

outline what happens during prophase

Answer 5

chromosomes condense
centrioles move to opposite poles of cells and mitotic spindle fibres form nuclear envelope and nucleolus break down-chromosomes free in cytoplasm

Question 6

outline what happens during metaphase

Answer 6

sister chromatids line up at equator attached to spindle fibres by centromeres

Question 7

outline what happens during anaphase

Answer 7

spindle fibres contract-centromeres divide
sister chromatids separate into 2 distinct chromosomes and pulled to opposite ends of cell
spindle fibres break down

Question 8

what happens during telophase

Answer 8

chromosomes decondense
new nuclear envelope forms around each set of chromosomes
2 new nuclei

Question 9

what happens during cytokinesis

Answer 9

cell membrane cleavage furrow forms
contractile division of cytoplasm

Question 10

how is cell cycle regulated

Answer 10

checkpoints ensure damage detected and do not progress

Question 11

what happens at G1 checkpoint

Answer 11

checks for DNA damage

Question 12

what happens at G2 checkpoint

Answer 12

checks chromosome replication

Question 13

what happens at metaphase checkpoint

Answer 13

cell checks sister chromatids have attached to spindle correctly

Question 14

what is meiosis

Answer 14

produces four genetically different haploid cells

Question 15

what happens during meiosis 1

Answer 15

homologous chromosomes pair to form bivalent
crossing over occurs at chiasmata
cell divides into two
homologous chromosomes separate randomly

Question 16

what are homologous chromosomes

Answer 16

pair of chromosomes with genes at same loci
1 maternal and 1 paternal

Question 17

what happens during meiosis 2

Answer 17

independent segregation of sister chromatids
each cell divides again forming 4 haploid cells

Question 18

how does meiosis produce genetic variation

Answer 18

crossing over during meiosis 1
independent assortment

Question 19

how do cells become specialised

Answer 19

some genes expressed while others silenced due to cell differentiation
cells produce proteins that determine their structure and function

Question 20

what is a transcription factor

Answer 20

a protein that controls transcription of genes so only certain parts of DNA expressed

Question 21

how do transcription factors work

Answer 21

move from cytoplasm to nucleus
bind to promoter region
make it easier or more difficult for RNA polymerase to bind to gene
increases or decreases rate of transcription

Question 22

what is a stem cell

Answer 22

undifferentiated cells that can divide indefinitely and turn into other specific types of cell

Question 23

name and define the four types of stem cell

Answer 23

totipotent-can develop into any cell type
pluripotent-can develop into any cell type (not placenta or embryo)
multipotent-can develop into a few types of cell
unipotent-can develop into any type of cell

Question 24

suggest some uses of stem cells

Answer 24

repair damaged tissue
drug testing
treating neurological diseases

Question 25

describe the 2 groups of specialised cells in blood

Answer 25

erythrocytes-biconcave, no nucleus, lots of haemoglobin to carry oxygen leucocytes-neutrophils to engulf foreign material

Question 26

how do specialised cells form in blood

Answer 26

multipotent stem cells in bone marrow differentiate into: erythrocytes leucocytes

Question 27

describe the structure of squamous epithelial cells

Answer 27

single smooth layer of squamous cells thin and flat with round nucleus fixed in place by basement membrane

Question 28

describe the structure of ciliated epithelial cells

Answer 28

column shaped with surface projections called cilia

Question 29

describe the structure and function of palisade cells

Answer 29

absorb light energy for photosynthesis contain many chloroplasts

Question 30

describe the structure and function of guard cells

Answer 30

form stoma when turgid stoma opens when flacid stoma closes walls thickened by spirals of cellulose

Question 31

describe the structure and function of root hair cells

Answer 31

absorb water and low concentration materials from soil hair like projections increase surface area for osmosis many mitochondria produce ATP for active transport

Question 32

what are meristems

Answer 32

totipotent undifferentiated plant cells

Question 33

describe the structure of phloem tissue

Answer 33

sieve tube elements-form tube to transport sucrose companion cells-involved in ATP production for active loading of sucrose into sieve tubes plasmodesmata-gaps between cell walls where cytoplasm links