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JH4 Biology > Cell Division > Flashcards

Cell Division Flashcards

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1
Q

What are the phases of the cell cycle?

A

G1 (First Gap) -> S (Replication of DNA) -> G2 (Second Gap) -> M Phase (Mitosis)

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2
Q

What is interphase of the cell?

A

G1, S and G2 Phases

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3
Q

What happens in the G1 Phase?

A

Cell is metabolically active and continuously grows

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4
Q

What happens in the S Phase?

A

DNA replication takes place -> each chromosome forms two sister chromatids connected at the centomere

  • DNA content doubled, twice as many chromatids as chromosomes in G1 phase
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5
Q

Describe the mechanism of DNA replication

A

Semiconservative mechanism -> DNA molecules with 1 parental strand and 1 daughter strand (from environment)

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6
Q

What happens in the G2 Phase?

A

Cell growth continues and proteins are synthesised in preparation for M phase

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7
Q

What are chromosomes and sister chromatids?

A

Chromosome -> Discrete unit of genetic material

Sister chromatid -> Copies of DNA produced after DNA replication

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8
Q

What are the phases of mitosis?

A

Prophase -> Metaphase -> Anaphase -> Telephase (PMAT)

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9
Q

Describe the prophase of mitosis

A
  • Chromatin fibres condense to form metaphase chromosomes
  • Mitotic spindle starts to form
  • Nuclear envelope completely disintegrates
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10
Q

What are kinetochore microtubules?

A

Binding of the microtubules of the mitotic spindle to the kinetochore protein located at the centromere of chromosomes

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11
Q

Describe the metaphase stage of mitosis

A
  • Metaphase chromosomes align themselves in a single file along metaphase plate
  • Kinetochore microtubules attach to kinetochore at centromeres of chromosomes
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12
Q

Describe the anaphase stage of mitosis

A
  • Kinetochore microtubules shorten
  • Sister chromatids seperate
  • Non-kinetochore microtubules lengthen to elongate the cell
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13
Q

Describe the telophase stage of mitosis

A
  • Daughter chromosomes decondense
  • Nuclear envelope reforms
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14
Q

Describe the cytokinesis process

A

!Occurs during telophase!
- Formation of cleavage furrow -> constricts to seperate cells (Animal)

  • Vesicles from golgi apparatus move along microtubules to the center of the cell -> coalesce to form cell plate (Plants)
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15
Q

Role of Mitosis

A
  • Enables growth in multicellular organisms
  • Repair of worn-out or damaged tissues in the body
  • Allows for unicellular organims to reproduce asexually
  • Produces genetically identical cells
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16
Q

What are homologous chromosomes?

A
  • Chromosomes that are the same size, centromere location and banding pattern
  • Same genes are located at same position, however alleles may differ
17
Q

What are haploids, diploids and polyploids?

A
  • Diploid cells carry 2 sets of chromosomes -> humans cells are diploid
  • Haploid cells contain one set of chromosomes -> gametes eg. egg and sperm
  • Polyploids contain three or more chromosomes
18
Q

What are the phases of Meiosis?

A

Stage 1: Prophase I -> Metaphase I -> Anaphase I -> Telephase I (Involves bivalents of homologous chromosomes)

Stage 2: Prophase II -> Metaphase II -> Anaphase II -> Telephase II (Involves chromomes with two sister chromatids)

19
Q

Describe Prophase I of meiosis

A
  • Homologous pairs undergo synapsis with each other to form a bivalent (verb: synapse)
  • Crossing over occurs between non-sister chromatids -> occurs at the chiasma
  • Nuclear envelope disintegrates
20
Q

Describe Metaphase I of Meiosis

A
  • Bivalents become attached to kinetochore microtubules
  • Independent assortment occurs as bivalents randomly align along the metaphase plate
21
Q

Describe Anaphase I of Meiosis

A

Kinetochore microtubules shorten, bivalents seperate to homologous chromosomes

22
Q

Describe Telophase I & Cytokinesis of Meiosis

A
  • Homologous chromosomes decondense
  • Nuclear envelopes reform
  • Cleavage furrow forms to seperate cell into two daughter cells
23
Q

What does Meiosis I produce?

A

Two diploid daughter cells containing homologous chromosomes

24
Q

How are Meiosis II and Mitosis similar and different?

A
  • Process of chromosomes seperating into sister chromatids is similar
  • Four stages of Prophase, Metaphase, Anaphase and Telophase are basically identical
  • Meiosis II produces 4 genetically different haploid gametes
  • Mitosis produces genetically identical cell with same DNA content as parent cell
25
Q

How does Meiosis promote genetic variation?

A
  1. Crossing Over in Prophase I
  2. Independent Assortment in Metaphase I
  3. Random fertilisation (only during fertilisation process)
26
Q

How does crossing over promote genetic variation?

A
  • Results in sister chromatids becoming non identical
  • Produces new combinations of alleles not present in parents
  • Results in gametes with a combination of various traits
27
Q

How does independent assortment promote genetic variation?

A
  • Bivalents line up randomly along metaphase plate and seperate
  • Each daughter cell receives a different combination of maternal and paternal
28
Q

What is nondisjunction?

A
  • Homologous chromosomes in Meiosis I or Sister chromatids in Meiosis II fail to seperate
29
Q

What is an allele?

A

The specific variant of a heritable feature that varies among individuals eg. black wing allele, speckled wing allele

JH4 Biology (10 decks)

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