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AS Level Biology Unit 1 > Cell Division > Flashcards

Cell Division Flashcards

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1
Q

what is cell cycle?

A

cellular events, that repeat in order between one cell division and the next. occurs in all body cells of multicellular organisms

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2
Q

what are the 3 stages in cell cycle?

A

interphase - cell growth, DNA replicates, cell organelles replicate, ATP is built up

mitosis- nucleus divides forming 2 genetically identical daughter nuclei

cytokinesis- cytoplasm divides to form 2 daughter cells

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3
Q

how much of the cell cycle is interphase ?

A

90%

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4
Q

another name for interphase?

A

resting stage

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5
Q

interphase

A

period of intense biochemical activity

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6
Q

what 3 stages is interphase subdivided into?

A

G1= cell increasing in size
Synthesis= DNA replicates, checking DNA for errors
G2= cell keeps increasing in size, protein synthesis, ATP stores built up

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7
Q

when does amount of DNA double?

A

at interphase

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8
Q

when are chromosomes visible?

A

when cell is dividing, otherwise they consist of a widely spread area of darkly stained material called chromatin

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9
Q

what are chromosomes in eukaryotic cells made up of?

A

70% protein(histones)
15% DNA
10% RNA

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10
Q

how many strands is a chromosome made up of ?

A

made up of 2 strands ( as DNA replicated in interphase) called sister chromatids joined by a centromere

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11
Q

what is loci?

A

where the gene is

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12
Q

how many chromosomes do humans have?

A

46 - half from father half from mother
23 and 23

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13
Q

what is ploidy level?

A

number of complete sets of chromosomes in an organism

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14
Q

what feature is used to put chromosomes in order?

A

size order

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15
Q

term used for ‘matching’

A

homologous

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16
Q

what pairs are autosomes?

A

1-22

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17
Q

what is the 23rd pair?

A

sex chromosomes

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18
Q

what chromosomes do males have?

A

X + Y

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19
Q

what chromosomes do females have?

A

X + X

20
Q

photograph used for chromosomes?

A

karyotype

21
Q

what is mitosis?

A

type of cell division in which two daughter cells have the same number of chromosomes and are genetically identical with each other and the parent cell
= giving genetic stability

22
Q

mitosis is needed in multicellular organisms for ?

A

genetic stability
growth of tissues
repair/replacement of tissues
asexual reproduction

23
Q

stages of mitosis

A

PMAT
Prophase
Metaphase
Anaphase
Telophase

24
Q

what occurs in prophase?

A
  1. chromosomes condense (shorten thicken) and become visible
  2. nucleolus disappears
  3. spindle develops
  4. nuclear envelope disintegrates
25
Q

what is a spindle?

A

protein microtubules

26
Q

what occurs in metaphase?

A
  1. chromosomes line up at the equator
27
Q

what occurs in anaphase?

A
  1. chromosomes split and chromatids separate
  2. spindles contracts and the chromatids are pulled to the opposite poles of the cell centromere first
28
Q

what does the movement of chromatids rely on?

A

cell cytoskeleton and ATP

29
Q

what occurs in telophase?

A
  1. spindle disintegrates
  2. nucleolus reforms
  3. nuclear envelope develops
30
Q

after telophase cytokinesis occurs, what happens in cytokinesis?

A

the cell membrane constricts around the equator, forming two daughter cells that are genetically identical to the original cell

31
Q

what does the term clones mean?

A

offspring are genetically identical to the original, parent organism

32
Q

budding in yeast cells

A
  1. parent yeast cell swells on one side, forming a bud at the cell surface
  2. the nucleus divides by mitosis
  3. the nucleus (and cell organelles and cytoplasm) move into the swelling/bud
  4. cytokinesis occurs and the bud pinches off and separates from the plant cell, producing a new genetically identical yeast cell
33
Q

differences in mitosis between animal cells and plant cells

A

ANIMAL
1. cells become rounded
2. occurs in most cells
3. centrioles form spindles
PLANT
1. no change in shape
2. only occurs in meristem
3. no centrioles (form from tubulin)

34
Q

what is cancer?

A

uncontrolled cell division

35
Q

what is a tumour?

A

an irregular mass of cells

36
Q

definition of an oncogene?

A

any gene that could potentially cause cancer

37
Q

what happens in stages of meiosis?

A

s phase= DNA is replicated so the mass of DNA doubles

meiosis i = the homologous pairs of a separate number of chromosomes half aswell as a mass of DNA

meosis ii= the sister chromatids seperate so each daughter cell has only one chromatid so mass of DNA halves again

38
Q

why must the chromosome number be halved in meiosis?

A

at fertilisation it will restore the diploid number

39
Q

meiosis i
prophase

A
  1. the chromosomes condense and become visible
  2. the chromosomes come together as homologous pair(a process called synapsis) each H is bivalent
  3. non-sister chromatids wrap round each other and attach at points called chiasmata
  4. they swap sections of chromatids with one another in a process called crossing over
  5. the nucleolus disappears and the nuclear envelope disintegrates
  6. centrioles move to opposite poles and spindle forms
40
Q

what is each homologous pair called?

A

bivalent

41
Q

what does crossing over do?

A

gives chromatids new combination of alleles

42
Q

metaphase i

A
  1. bivalents line up at the equator of the cell randomly, attached to spindle fibres at their centromeres
  2. this allows independent assortment
43
Q

what is independent assortment ?

A

process where the chromosomes move randomly to separate poles

44
Q

with 23 pairs of chromosomes there are ..

A

2^23

45
Q

anaphase i

A
  1. the homologous chromosomes in each bivalent are separated, spindle shortens, and chromosomes are pulled to opposite poles
  2. the centromeres do not divide
46
Q

telophase i

A
  1. the nuclear envelope reforms around each set of haploid chromosomes
  2. there is a brief interphase and the chromosomes uncoil

the cell now divides by mitosis

47
Q

meiosis ii

A

PROPHASE II
nuclear envelope breaks down and nucleolus disappears
chromosomes condense
spindles form
METAPHASE II

the chromosomes line up at equator and attach to spindles by centromere
independent assortment occurs because the chromatids of the chromosomes can face either pole - increases GENETIC VARIATION
ANAPHASE II

the centromeres split and the chromatids are pulled to opposite poles
TELOPHASE II

nuclear envelope and nucleoli reform and the spindle disintegrates
the chromosomes elongate and are no longer visible

CYTOKINESIS OCCURS
4 haploid, genetically different daughter cells

AS Level Biology Unit 1 (10 decks)

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