Cell Cycle Flashcards

1
Q

What is the cell cycle?

A

A regulated cycle of division with intermediate growth periods

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2
Q

What are the phases?

A

Interphase, mitosis or meiosis (nuclear division), cytokinesis.

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3
Q

What happens during interphase?

A

G1: cell synthesises proteins for replication e.g. tubulin for spindle fibres and cell size doubles
S: DNA replicates = chromosomes consist of 2 sister chromatids joined at centromere
G2: Organelles divide

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4
Q

What is the purpose of mitosis?

A

It produces 2 genetically identical daughter cells for growth, cell replacement/tissue repair and asexual reproduction. It has 4 stages, prophase, metaphase, anaphase and telophase.

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5
Q

What happens during prophase?

A

Chromosomes condense becoming visible, centrioles move to opposite poles of cell (animal cells) and mitotic spindle fibres form. Nuclear envelope and nucleolus break down = chromosomes free in the cytoplasm

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6
Q

What happens during metaphase?

A

Sister chromatids line up at the cell equator, attached to the mitotic spindle by their centromeres.

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7
Q

What happens during anaphase?

A

Requires energy from ATP hydrolysis. Spindle fibres contract= centromeres divide. Sister chromatids separate into 2 distinct chromosomes and are pulled to opposite poles of cell. spindle fibres break down.

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8
Q

What happens during telophase?

A

Chromosomes decondense, becoming invisible again. New nuclear envelopes form around each set of chromosomes = 2 new nuclei, each with 1 copy of each chromosome

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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 the cell cycle regulated?

A

By checkpoints which are regulated by cell-signalling proteins, ensure damaged cells do not progress to next stage of cycle.

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11
Q

What does the checkpoint between G1 and S check for?

A

For DNA damage
After restriction point cell enters.

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12
Q

What does the checkpoint between G2 and M check for?

A

Cell checks chromosomes replication

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13
Q

What does the metaphase checkpoint check?

A

That sister chromatids have attached to spindle correctly.

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14
Q

What is meiosis?

A

A form of cell division that produces four genetically different haploid cells (half number of chromosomes found in parent cell) - gamete’s.

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15
Q

What happens meiosis 1?

A

Homologous chromosomes pair to form bivalents. Crossing occurs at chiasmata. Cell divides into two. Homologous chromosomes separate randomly. Each cell contains either a maternal or paternal copy.

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16
Q

What happens during meiosis 2?

A

Independent segregation of sister chromatids. Each cell divides again, producing 4 haploid cells

17
Q

How does meiosis produce genetic variation?

A

Crossing over during meiosis 1, independent assortment (random segregation) of homologous chromosomes and sister chromatids - results in new combination of alleles.