Cell Division Flashcards

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1
Q

what is the cell cycle and its stages

A

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

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2
Q

outline what happens during interphase

A

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

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3
Q

what is the purpose of mitosis

A

produce two genetically identical daughter cells
growth
cell replacement
asexual reproduction

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4
Q

name the stages of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

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5
Q

outline what happens during prophase

A

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

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6
Q

outline what happens during metaphase

A

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

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7
Q

outline what happens during anaphase

A

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

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8
Q

what happens during telophase

A

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

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9
Q

what happens during cytokinesis

A

cell membrane cleavage furrow forms
contractile division of cytoplasm

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10
Q

how is cell cycle regulated

A

checkpoints ensure damage detected and do not progress

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11
Q

what happens at G1 checkpoint

A

checks for DNA damage

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12
Q

what happens at G2 checkpoint

A

checks chromosome replication

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13
Q

what happens at metaphase checkpoint

A

cell checks sister chromatids have attached to spindle correctly

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14
Q

what is meiosis

A

produces four genetically different haploid cells

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15
Q

what happens during meiosis 1

A

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

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16
Q

what are homologous chromosomes

A

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

17
Q

what happens during meiosis 2

A

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

18
Q

how does meiosis produce genetic variation

A

crossing over during meiosis 1
independent assortment

19
Q

how do cells become specialised

A

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

20
Q

what is a transcription factor

A

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

21
Q

how do transcription factors work

A

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

22
Q

what is a stem cell

A

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

23
Q

name and define the four types of stem cell

A

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

24
Q

suggest some uses of stem cells

A

repair damaged tissue
drug testing
treating neurological diseases

25
Q

describe the 2 groups of specialised cells in blood

A

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

26
Q

how do specialised cells form in blood

A

multipotent stem cells in bone marrow differentiate into:
erythrocytes
leucocytes

27
Q

describe the structure of squamous epithelial cells

A

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

28
Q

describe the structure of ciliated epithelial cells

A

column shaped with surface projections called cilia

29
Q

describe the structure and function of palisade cells

A

absorb light energy for photosynthesis
contain many chloroplasts

30
Q

describe the structure and function of guard cells

A

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

31
Q

describe the structure and function of root hair cells

A

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

32
Q

what are meristems

A

totipotent undifferentiated plant cells

33
Q

describe the structure of phloem tissue

A

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