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Biology Module 2 > The Cell Cycle > Flashcards

The Cell Cycle Flashcards

1
Q

What is the cell cycle?

A
  • division of a cell resulting in formation of two genetically identical daughter cells.
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2
Q

What happens during interphase?

A
  • DNA is replicated and checked for errors in the nucleus
  • protein synthesis occurs in cytoplasm
  • mitochondria grow and divide, increasing in number in the cytoplasm
  • normal metabolic processes of cells occur
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3
Q

What are the three stages of interphase called?

A
  • G1
  • S
  • G2
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4
Q

What happens in the G1 phase of interphase?

A
  • first growth phase
  • proteins from which organelles are synthesised and produced and organelles replicate
  • the cell increases in size
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5
Q

What happens in the S phase of interphase?

A
  • synthesis

- DNA is replicated in the nucleus

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6
Q

What happens in G2 phase of interphase?

A
  • second growth phase
  • cell continues to increase in size
  • energy stores are increased
  • duplicated DNA is checked for errors
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7
Q

What phases are in the cell cycle?

A
  • interphase
  • mitosis
  • cytokinesis
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8
Q

What is mitosis?

A
  • nuclear division
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9
Q

What is cytokinesis?

A
  • cytoplasm divides and two cells are produced
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10
Q

When does the G0 stage happen permanently?

A
  • differentiation: cell that has become specialised for specific function can no longer divide
  • DNA become damaged, so no longer viable and won’t divide
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11
Q

What is the G0 phase?

A
  • name given to the phase when the cell leaves the cell cycle
  • temporary or permanently
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12
Q

When might the GO stage happen temporarily?

A
  • white blood cells in an immune response
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13
Q

What do checkpoints do in the cell cycle?

A
  • control mechanisms
  • monitor and verify whether the process at each stage of the cell cycle have been accurately completed before the cell is allows to progress to next stage
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14
Q

What is the G1 checkpoint and what does it check for?

A
  • end of G1 phase and before S phase

- checks for: cell size, nutrients, growth, DNA damage

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15
Q

What is the G2 checkpoint and what does it check for?

A
  • end of G2 phase before mitosis

- checks for: cell size, DNA replication and DNA damage

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16
Q

What is the spindle assembly checkpoint and what does it check for?

A
  • at the point in mitosis where all chromosomes are attached to spindles and aligned
  • checks for: chromosome attachment to spindle
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17
Q

What happens if a checkpoint fails?

A
  • cell is fixed/modified

- apoptosis (self destruction)

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18
Q

What is the difference between mitosis and cytokinesis?

A
  • mitosis is the process of replicating and dividing the genome
  • cytokinesis is the physical division of the cell
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19
Q

What is the importance of the G2 checkpoint?

A
  • DNA has been checked for errors
  • change in sequence of bases is a mutation
  • leads to change in amino acid sequence
  • function of protein dependent on 3D shape/tertiary structure
  • tertiary structure dependent on primary structure
  • primary structure is sequence of amino acids
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20
Q

What is a disadvantage of indefinite cell division?

A
  • mutations occur during DNA replication
  • indefinite replication increases chances of mutation/accumulation of mutations
  • increased chance of harmful mutation
21
Q

How is DNA usually replicated in eight hours in a eukaryotic cell?

A
  • many origins of replication

- idea that simultaneous replication of different lengths

22
Q

Why does it takes a shorter time to replicate the genome of a prokaryotic cell?

A
  • genome is shorter

- has fewer genes/has no introns

23
Q

What is mitosis?

A
  • nuclear division before cell physically divides in two
24
Q

Why is mitosis so important?

A
  • new cells for growth and repair
  • asexual production in eukaryotic cells e.g. amoeba species
  • prokaryotic cells don’t have nucleus so go through process of binary fission
25
Q

What’s a chromatid?

A
  • two identical copies of DNA makes up chromosome in cell division
26
Q

What’s a chromosome?

A
  • a strand of genetic material in nucleus.

- each chromosome consists of DNA and histones

27
Q

What’s an allele?

A
  • different forms of the same gene
28
Q

What’s crossing over?

A
  • genetic info shared between homologous chromosomes
29
Q

What’s a bivalent?

A
  • pair of homologous chromosomes line up in prophase 1
30
Q

What are histones?

A
  • proteins associated with chromosomes
31
Q

What is an homologous pair?

A
  • pair of equivalent chromosomes with same structure and arrangement of genes
32
Q

What happens in early prophase in mitosis?

A
  • chromatin condenses and becomes inactive
  • centrioles migrate in pairs to opposite poles
  • nucelar envelope and nucleolus breaks up
33
Q

What happens in late prophase in mitosis?

A
  • chromosomes tightly coiled and visible as separate under microscope
  • mitotic spindle begins to form at centrioles
34
Q

What happens in metaphase in mitosis?

A
  • mitotic spindle grows further and attaches to centromere of each chromosome
  • fibres then arrange chromosomes to line up along the cell equator
35
Q

What happens in anaphase in mitosis?

A
  • centromere of each chromosome breaks
  • sister chromatids separate into daughter chromosomes
  • cell starts to elongate as cytokinesis begins
36
Q

What happens in telophase in mitosis?

A
  • new nuclear membranes and nucleoli form

- chromosomes start to unwind back into chromatin and are no longer visible under microscope

37
Q

What is cytokinesis?

A
  • cytoplasm is divided between two daughter cells

- each new cell enters interphase and resumes normal functions

38
Q

How is cytokinesis different in plants and animals?

A
  • plants have cell wall so cannot form cleavage furrow

- vesicles form instead to form new membrane and cell wall

39
Q

Explain why we normally see chromosomes as a double structure containing two chromatids?

A
  • chromosomes only become visible under the microscope during mitosis
  • DNA needs to replicate for cell division. Chromosomes consist of two sister chromatids, which are identical copies of DNA.
40
Q

Why is it essential that DNA replication results in two exact copies of the genetic material?

A
  • so each daughter cell has identical DNA after mitosis/cell division
  • and correct number of chromosomes
  • diploid after mitosis and haploid after meiosis
41
Q

Why are plant root tips are a good source of cells to examine for mitosis?

A
  • they continually grow at regions called meristems
  • meristems are good source of cells for studying mitosis as they are constantly dividing
  • plant cells are easy to obtain and prepare for microscopy
42
Q

What happens in prophase 1 in meiosis?

A
  • chromosomes condense
  • nuclear envelope disintegrates
  • spindle fibres begin to form
  • homologous chromosomes pair up forming bivalents
  • crossing over occurs
43
Q

What happens in metaphase 1 in meiosis?

A
  • chromosomes line on cell equator
  • spindle fibres attach to the centromeres
  • independent assortment occurs
44
Q

What happens in anaphase 1 in meiosis?

A
  • homologous chromosomes are pulled (not apart) by the spindle fibres to the poles
  • causes genetic variation
45
Q

What happens in telophase 1 in meiosis?

A
  • nuclear envelopes reform
  • chromosomes uncoil
  • undergoes cytokinesis
  • haploid cells formed
46
Q

How is meiosis similar to mitosis?

A
  • exactly the same, apart from 4 haploid daughter cells produced
47
Q

What causes genetic variation in meiosis and how?

A
  • crossing over and independent assortment
  • reduction (fertilisation)
  • 23 chromosomes in haploid so lots of different combinations
48
Q

Why is a reduction division necessary in the production of gametes?

A
  • gametes are the sex cells and two sex cells must combine to produce a diploid offspring
  • therefore gametes must contain only half the number of chromosomes/DNA
  • be haploid otherwise with each new generation the number of chromosomes would increase
49
Q

What is the importance of the creation of different allele combinations in populations?

A
  • creating different allele pairs during meiosis is an important source of genetic variation in a population
  • genetic variation is important for the process of natural selection
  • gives individuals in a population characteristics that might confer an advantage in changing environment
  • e.g. pathogen resistance
  • if no genetic variation the entire population would be vulnerable to such an external factor and there would be no opportunity for adaptation

Biology Module 2 (16 decks)

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