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Biology > Cell division and Cell cycle A1 > Flashcards

Cell division and Cell cycle A1 Flashcards

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1
Q

What is mitosis?
(3)

A
  1. cell division
  2. which increases cell growth and repair
  3. to produce two genetically identical daughter cells
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2
Q

Why must DNA replication take place before cell division?

A

because the two daughter cells need one copy of each of DNA it cannot be halved as there wouldn’t be a full set.

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3
Q

Define chromosone.

A

an independent DNA molecule which has folded into a condense form (contains genes) (two sister chromatids together)

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4
Q

Define gene.

A

a section of DNA coding for one polypeptide protein

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5
Q

Define sister chromatids.

A

two identical copies of the same chromosome formed in DNA replication

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6
Q

Define homologous chromosomes.

A

have the same genes in same position but different alleles (version) of the genes

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7
Q

Define…
-diploid
-haploid

A

diploid - two copy of each chromosome
haploid - one copies of each chromosome (one from each parent)

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8
Q

Name the phases of mitosis in order.

A
  1. prophase
  2. metaphase
  3. anaphase
  4. telophase
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9
Q

Describe the features of prophase.
(3)

A
  1. nuclear membrane begins to break down
  2. centrioles move to poles of the cell
  3. chromosomes condense
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10
Q

Describe the features of metaphase.
(4)

A
  1. spindle fibres form
  2. spindle fibres attach
  3. to the centromere of chromosomes
  4. chromosomes align at the equator
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11
Q

Describe the features of anaphase.
(4)

A
  1. spindle fibres shorten
  2. centromere splits
  3. sister chromatids are separated
  4. pulled to opposite poles of the cell
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12
Q

Describe the features of telophase.
(2)

A
  1. nuclear membrane begins to reform
  2. chromosomes unwind
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13
Q

Describe and explain the stages of the phase that occurs before mitosis.
(4)

A
  1. interphase (stages of interphase below)
  2. G1 phase - cell increases in size and new biomass is made
  3. S phase - DNA replicates
  4. G2 phase - cell gets ready for division, it makes stores of ATP and new organelles
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14
Q

What comes after mitosis?
(2)

A
  1. cell division (cytokinesis)
  2. period when cell divides into two, each daughter cell receiving one of the nuclei
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15
Q

Define the end product of mitosis.
(4)

A
  1. daughter cells are genetically identical to each other
  2. and to original parent cell
  3. no variation occurs
  4. they have the same number of chromosomes as the parent cell
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16
Q

Describe the appearance and behaviour of chromosomes during mitosis.
(8)

A
  1. during prophase, chromosomes supercoil and condense to become visible
  2. chromosomes appear as two identical sister chromatids joined by a centromere
  3. during metaphase, chromosomes line up on equator of cell
  4. chromosomes attach to spindle fibres
  5. by their centromere
  6. during anaphase, the centromere splits
  7. sister chromatids are pulled to opposite sides of the cell making a V shape
  8. during telophase, chromatids uncoil and become thinner
17
Q

How is cancer caused?
(4)

A
  1. mutation occurs in a control gene
  2. so cell division continues uncontrollable
  3. division is rapid and cells produced are abnormal
  4. a tumour develops (cancer)
18
Q

How may cancer be treated?
(2)

A
  1. drugs that stop cell division (mitosis)
  2. the drugs may stop DNA replication, spindle formations, cytokinesis or other processes linked to mitosis
19
Q

What is binary fission?
(4)

A
  1. splitting in two (asexual reproduction of prokaryotes eg. bacteria)
  2. DNA and plasmids replicated
  3. cell elongates in middle, separating DNA molecules, new cell wall is formed
  4. its very fast and simple
20
Q

What is the endosymbiont theory?

A

the theory that mitochondria and chloroplasts were once prokaryotic as they replicate via binary fission like prokaryotes.

21
Q

How do viruses replicate?
(4)

A
  1. the protein molecules on capsid attach to cell surface membrane of host cells
  2. the virus enters the cell as its genetic material hijacks the machinery of the cell
  3. the cell copies the viruses DNA or RNA (using reverse transcriptase), makes new proteins coat and assembles the new virus
  4. eventually these burst out the cell destroying it
22
Q

name the conversions for…
- nanometers (nm) to micro-meters (μm)
- micro-meters to milli-meters
- milli-meters to meters

A
  • 1000 nm in a micro-meter
  • 1000 micro-meters in a milli-meter
  • 1000 mm in a meter
23
Q

What’s the purpose of the root tip squash experiment?
(5)

A
  1. growth in plants occurs in specific regions called meristems
  2. the root tip meristem can be used to study mitosis
  3. the root tip meristem can be found just behind the protective root cap
  4. in the root tip meristem, there is a zone of cell division that contains cells undergoing mitosis
  5. pre-prepared slides of root tips can be studied or temporary slides can be prepared using the squash technique (root tips are stained and then gently squashed spreading the cells out into a thin sheet and allowing individual cells undergoing mitosis to be clearly seen)
24
Q

What’s the equation for mitotic index?

A

mitotic index = (number of cells with visible chromosomes ÷ total number of cells)
X
100 (to get a %)

25
Q

Meiosis results in cells that have the haploid number of chromosomes and show genetic variation.
Explain how.
(7)

A
  1. homologous chromosomes pair up
  2. maternal and paternal chromosomes are arranged in any order
  3. independent segregation
  4. crossing over
  5. portions of chromatids are swapped between chromosomes
  6. produces new combinations of alleles
  7. chromatids separate at meiosis II/ later
26
Q

Explain crossing over and how it leads to a varied population.
(3)

A
  1. crossing over leads to exchange of parts/segments of non-sister chromatids/alleles
  2. between homologous chromosome pairs
  3. this creates new combinations of alleles in the gametes
27
Q

Explain independent segregation and how it leads to a varied population.
(5)

A
  1. during metaphase of first division
  2. homologous chromosomes attach to spindle fibres and pair up side by side
  3. they are shuffles into any recombination
  4. this produces new combinations of characteristics
  5. meaning the members of species with advantageous alleles will be able to survive if environment changes
28
Q

How do you calculate the number of different combinations possible during independent segregation?

A
  1. n = number of chromosomes
  2. 2 to the power of n
  3. eg if n = 3, 2 to the power of 3 = 8
29
Q

Describe and explain the process that occurs during meiosis that increases genetic variation.
(5)

A
  1. homologous chromosomes pair up
  2. independent segregation
  3. maternal and paternal chromosomes are re-shuffled in any combination
  4. crossing over leads to exchange of parts/segments of (non-sister) chromatids/alleles between homologous chromosomes
  5. both create new combinations of alleles
30
Q

Describe binary fission in bacteria.
(3)

A
  • replication of circular DNA
  • replication of plasmids
  • division of cytoplasm

Biology (27 decks)

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