Cell cycle Flashcards

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1
Q

What is the cell cycle?

A

A sequence of events that leads to the reproduction of a cell

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2
Q

Before cell division

A
  • Chromosome replication and segregation
  • Cell growth
  • Separation of organelles
  • Gap phases (provides time for cell growth)
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3
Q

How does the cell cause cell division?

A

When cells grow DNA/mass ratio decreases. Then chromosomes and DNA duplicate causing an increase in ratio and so the cell doubles in size for division

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4
Q

What are the 4 nitrogenous bases in DNA?

A

Adenine, guanine, thymine and cytosine

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5
Q

What is the basic structure of DNA?

A

Nitrogenous bases connected together via pentose sugars and phosphate

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6
Q

Eukaryotic DNA replication

A
  • Takes place in nucleus
  • 4+ types of polymerases
  • Slow
  • Occurs in S phase
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7
Q

Prokaryotic DNA replication

A
  • Takes place in cytosol
  • 1-2 types of polymerases
  • Fast
  • Occurs throughout cell cycle
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8
Q

1st step of DNA replication

A

2 strands of DNA are in a straight bond which is then separated by an initiator protein to form a replication bubble

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9
Q

2nd step of DNA replication

A

DNA becomes untwisted by DNA helicases to form a Y shaped replication fork by breaking hydrogen bonds between bases

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10
Q

3rd step of DNA replication (single-stranded DNA-binding (SSB))

A

2 single-stranded template strands are formed which bind to proteins to prevent re-joining

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11
Q

What are DNA topoisomerases?

A

They are part of SSB and relieve tension

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12
Q

4th step of DNA replication

A

RNA primase synthesises a short RNA primer which attaches to a template strand

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13
Q

5th step of DNA replication

A

DNA polymerase causes the addition of nucleotides to the RNA primer where it forms a base pair with a nucleotide on the template strand of DNA

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14
Q

What are Okazaki fragments?

A

Small fragments of DNA nucleotides

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15
Q

What are the 4 periods of the cell cycle?

A

G1, G2, M and S

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16
Q

G1 period

A
  • Cell growth
  • Preparation of chromosomes for replication
  • Duplication of cell components
17
Q

S period

A
  • When DNA is made
  • Each chromosome has many origins of replication
18
Q

G2 period

A
  • Cell prepares for M period
  • Genes are expressed
19
Q

M period

A
  • Mitosis or meiosis occurs
  • Chromosomes are condensed and separated
  • Cell divides
20
Q

Mitosis

A
  • Occurs in somatic or body cells
  • Asexual reproduction for healing cells and growth and development of cell body
  • One cell division
  • 4 stages of cell division
  • No independent assortment at metaphase
  • Separation of sister chromatids at anaphase
21
Q

Meiosis

A
  • Occurs in reproductive cells
  • Only needed for sexual reproduction
  • 2 cell divisions
  • 8 stages of cell division
  • Independent assortment of homologous chromosomes at metaphase
  • Separation of homologous chromosomes and sister chromatids at anaphase