cell cycle and division Flashcards

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1
Q

cell cycle definition

A

a regulated process in a sequence of events which cells divide into daughter cells in complete cell division. this consists of three main stages: interphase, mitosis and cytokinesis

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2
Q

interphase part of cell cycle

A

G1, S, G2
phase between divisions
DNA is unwound as chromatin so genes are accessible for transcription
cells are metabolically active
cell growth and DNA replication occurs

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3
Q

S

A

signal received causing cell division
DNA replicates and is synthesised
amount of DNA doubles

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4
Q

G1 phase

A

cells make RNA, enzymes and other proteins for growth
organelles are replicated

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5
Q

G2 phase

A

cell continues to grow
new DNA is syhthesised and checked

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6
Q

mitosis products

A

2 genetically identical diploid daughter cells

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7
Q

mitosis function

A

growth. (increasing cell number), repair of damaged tissues and asexual reproduction

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8
Q

staged of mitosis in order

A

Prophase, Metaphase, Anaphase, Telophase

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9
Q

prophase

A

chromosomes condense (now visible if stained)
two centrioles move towards opposite poles
nuclear envelope break down (now visible on light microscope)
Nucleolus disappears
Spindle fibres form

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10
Q

metaphase

A

centrosomes reach opposite poles
spindle fibres extend from centrosome
chromosomes line up at the equator
spindle fibres reach chromosomes and attach to centromere
each sister chromatid is attached to a spindle fibre originating from opposite poles

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11
Q

anaphase

A

sister chromatids separate at the centromere
spindle fibres begin to shorten
separated sister chromatids (chromosomes) are pulled to opposite poles by spindle fibres

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12
Q

telophase

A

chromosomes arrive at opposite poles and begin to decondense
nuclear envelope reforms
spindle fibres break down

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13
Q

Formation of specialised cells from stem cells

A

Chemical stimulus (e.g. growth substance)
Genes activated
Active genes transcribed
mRNA translated to make proteins
Proteins modify cell structure and function permanently

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14
Q

Things which are only observed in meiosis

A

Chiasmata
Pairing of homologous chromosomes
Synapsis
Formation of bivalents

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15
Q

How generic variation occurs in meiosis

A

Crossing over and independent assortment
CO: crossing over sections of chromatid
IA: random selection of maternal and paternal chromosomes by spindle fibres in metaphase 1
Causing new allele combinations

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