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BIOSCI 107 > Lecture 10: CSF Cell Division > Flashcards

Lecture 10: CSF Cell Division Flashcards

1
Q

Do all cells in one human have the same DNA?

A

Yes

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2
Q

How are cells different even though they contain the same DNA?

A

Different parts of DNA (genes) are expressed

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3
Q

What are the 3 possible outcomes for a cell?

A

Live and function without dividing

Grow and divide

Die

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4
Q

What are somatic cells?

A

Body cells (all cells excluding gametes) - diploid (2n)

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5
Q

Why do somatic cells need to divide?

A

Tissue replacement

Growth

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6
Q

What is mitosis?

A

The division of a diploid cell to form two identical diploid daughter cells

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7
Q

What is meiosis?

A

The division of a diploid cell to form four haploid sex cells with different genetical information to parent cell

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8
Q

What are the steps of the eukaryotic cell cycle?

A

Mitotic phase -> G1 phase -> S phase -> G2 phase -> mitotic phase

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9
Q

What is interphase?

A

G1 phase S phase and G2 phase

Most cells of the body are performing there functions in interphase.

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10
Q

What occurs in the G1 phase?

A

Most cellular activities - the duration varies from cell to cell

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11
Q

What occurs in the S phase?

A

DNA replication - 23 sets of chromosomes before exist as single chromatids, they become 23 sets of chromosomes which are formed from two sister chromatids pairing up

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12
Q

What occurs in the G2 phase?

A

Checks for correct DNA synthesis
Preparation for mitosis (synthesis of proteins and enzymes, gathering of reactants)
Replication of centrosomes (made up of centrioles which organise microtubules)

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13
Q

What are the steps of the mitotic phase?

A 
Prophase (early and late)
Metaphase
Anaphase
Telophase
Cytokinesis
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14
Q

What occurs in prophase of mitosis?

A 
DNA condenses (existing as two identical chromatids per chromosome - sister chromatids)
Mitotic spindle begins forming
Nuclear envelope breaks down
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15
Q

What occurs in metaphase of mitosis?

A

Condensed chromosomes align at the equator via their centromeres

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16
Q

What occurs in the anaphase of mitosis?

A

The microtubules contract pulling apart sister chromatids to each end of the cell

17
Q

What occurs in the telophase of mitosis?

A

Nuclear envelope reforms

Cleavage furrow

18
Q

What are diploid cells?

A

Cells with 2 sets of chromosomes

19
Q

What are haploid cells?

A

Cells with only 1 set of chromosomes (sex cells)

20
Q

At what points do checkpoints exist for the mitotic cycle?

A

At the end of G1 phase (G1 checkpoint)
At the end of G2 phase (G2 checkpoint)
At the end of metaphase during mitosis (M checkpoint)

21
Q

What is the G1 checkpoint?

A

Checkpoint near the end of G1 phase that checks for:

  • Is the DNA undamaged?
  • Is cell size and nutrition ok?
  • Appropriate signals present?
22
Q

What happens if a cell does not pass the G1 checkpoint?

A

Enters G0

23
Q

What is the M checkpoint

A

Checkpoint at the end of metaphase to check whether all chromosomes have been attached to the equator of the spindle

24
Q

Where does meiosis occur?

A

In the gonads (testes and ovaries)

25
Q

What are the two stages of meiosis?

A 
Meiosis I:
Prophase I
Metaphase I
Anaphase I
Telophase I
Meiosis II:
Prophase II
Metaphase II
Anaphase II
Telophase II
26
Q

What occurs in meiosis I?

A

Separation of homologous chromosomes (diploid to haploid)

A diploid parent cell divides forming two haploid daughter cells with non-identical genetic information

27
Q

What are homologous chromosomes

A

Homologous chromosomes are chromosomes that share the same structure and gene loci - one from female and one from male in human

28
Q

What is synapsis?

A

When two sister chromatids of each pair of homologous chromosomes pair up

= two chromosomes, each with two sister chromatids paired up, that have the same structure and gene loci, pair up

A 4 chromatid structure called a tetrad is formed

29
Q

What is a tetrad?

A

A 4 chromatid structure formed from synapsis in which homologous chromosomes each with 2 sister chromatids paired up pair up.

30
Q

What occurs in prophase I of meiosis?

A

Homologous chromosomes pair up
Nuclear envelope breaks down
Spindle begins forming
Crossing over occurs - non-sister chromatids (chromatids from different chromosomes) pair up forming chiasmata and exchange genetic information

31
Q

What is chiasmata?

A

Overlap of non-sister chromatids in a homologous pair of chromosomes

32
Q

What is crossing over?

A

Exchange of genetic information between non-sister chromatids in a homologous pair of chromosomes during prophase I.

33
Q

What occurs in metaphase I of meiosis?

A

The kinetochore (at centromere) of homologous chromosomes line up at the equator of the spindle

Independent assortment - the random splitting of homologous chromosomes at the equator during metaphase I

34
Q

What occurs during anaphase I of meiosis?

A

The homologous chromosomes separate

Sister chromatids remain attached

35
Q

What occurs during telophase I of meiosis?

A

Cleavage furrows

36
Q

What occurs during meiosis II?

A

Each of the 2 daughter haploid cells divide in a process identical to mitosis forming 4 daughter haploid cells

37
Q

What are the 3 sources of genetic variation and at what points do they occur?

A

Crossing over - prophase I
Independent assortment - metaphase I
Fertilisation - fusion between two gametes

BIOSCI 107 (29 decks)

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