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Biology A level > 2.2 Cell Division > Flashcards

2.2 Cell Division Flashcards

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1
Q

What is the cell cycle?

A

The sequence of dividing and non-dividing stages of the life of a cell

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2
Q

What is interphase of the cell cycle?

A

It is the non-dividing stage and the longest stage

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3
Q

What are the main stages of the cell cycle?

A

G1 phase = cell growth
S phase = DNA replication
G2 phase = prep for mitosis
Cell division = mitosis

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4
Q

What does diploid mean?

A

2 sets of chromosomes with homologous pairs
1 paternal set and 1 maternal set

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5
Q

What does haploid mean?

A

1 set of chromosomes no homologous pairs
A mix of paternal and maternal chromosomes

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6
Q

What type of cells are diploid?

A

Somatic cells= human cells

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7
Q

What type of cells are haploid?

A

Gametes

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8
Q

How can you tell if a cell has not undergone cytokinesis?

A

They have multiple nuclei because the nuclear division has taken place but the cytoplasm hasn’t split

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9
Q

What is a chromosome?

A

Condensed chromatin

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10
Q

What is chromatin?

A

DNA double helix that is bound to histones

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11
Q

If an haploid organism undergoes mitosis what type of cell (hap/dip) does it produce?

A

Haploid

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12
Q

What type of cells does mitosis take place in?

A

Eukaryotic

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13
Q

What is mitosis?

A

Nuclear division in eukaryotic cells that produces 2 genetically identical daughter cells

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14
Q

Are the daughter cells haploid or diploid in mitosis?

A

Diploid

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15
Q

What are the stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

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16
Q

What happens during interphase of mitosis?

A

The cell makes a copy of its DNA - DNA replication
Cell growth
The chromosomes are not visible ATP synthesis
Synthesis of organelles

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17
Q

What happens during prophase of mitosis?

A

Chromosomes coil - condense and shorten and become visible
Spindle fibres form from each pair of centrioles
Chromosomes attach to spindle fibres by their centromere
Nucleolus disappears
Nuclear envelope breaks down, chromosomes are free in the cytoplasm

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18
Q

What happens during metaphase of mitosis?

A

Chromosome are pulled along the spindle fibres and align themselves across the equator of the cell
The centromeres divide into two

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19
Q

What happens during anaphase of mitosis?

A

Spindle fibres contract and shorten, pulling sister chromatids apart
Chromosomes are pulled to opposite poles

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20
Q

What do mitochondria do in anaphase?

A

Mitochondria located around the spindle fibres provide ATP for contractions

21
Q

What happens during telophase of mitosis?

A

Chromosomes reach their respective poles
Nuclear envelope and nucleoli reform
Spindle fibres disintegrate
Chromosomes become elongated becoming less visible

22
Q

What happens during cytokinesis during mitosis?

A

Cell membrane pinches inwards separating the cytoplasm
Cytoplasm divides to produce two new cells

23
Q

What is the importance of mitosis?

A

Responsible for cell growth for tissues and organisms
Tissue repair
Asexual reproduction in single cells eukaryotes

24
Q

How would you identify prophase from a diagram?

A

The chromosomes are random and have no specific arrangement and they are visible

25
Q

What is an advantage of genetically identical offspring to parents?

A

In an unchanging environment, successful parents rapidly produce successful offspring

26
Q

What is a disadvantage of having genetically identical offspring to parents?

A

The offspring are more vulnerable to changes in the environment like disease

27
Q

How do you calculate t he mitotic index?

A

No. Of cells undergoing mitosis: total no. Of cells

28
Q

Why do you use a root in the root tip squash prac?

A

It is the growth region where mitosis occurs
no dividing cells more than 5mm from tip
to get soft tissue to squash
so it will fit under the cover slip

29
Q

Why is a stain necessary in the root tip prac?

A

So the chromosomes become visible to view under the microscope

30
Q

Why is the root tip added to HCl?

A

To soften the cell wall so the stain can enter the cell quickly

31
Q

What stain is used in the root tip prac?

A

Acetic orcein

32
Q

Why is the watch glass with the root and HCL placed in a hot water bath?

A

It speeds up the movement of the stain and the softening of the cell walls

33
Q

Why do you need to squash the root tip?

A

Makes it thin to get a single layer of cells to see the chromosomes under the microscope

34
Q

What is the root tip prac?

A
  1. Cut 5mm off garlic root tip
  2. Add one drop of 1M HCl and place in waterbath for 10mins
    3.put 10 drops of acetic orcein stain
  3. Add the root tips
  4. Using forceps, remove a root tip and place it on a microscope slide. Place a cover slip over the top
  5. Immediately place filter paper over the cover slip then use thumb to gently squash the root tip
35
Q

How do prokaryotes divide?

A

Binary fission

36
Q

What is the process of binary fission?

A
  1. Circular DNA replicates and both copies attach to cell membrane. Plasmids also replicate
  2. Cell membrane begins to grow between two DNA molecules
  3. Cell membrane begins to pinch inwards dividing the cytoplasm
  4. A new cell wall forms between the two molecules of DNA fully dividing the original cell
  5. Two new identical daughter cells formed with a single copy of the circular DNA and a variable no. Of plasmids
37
Q

What is the process of replication in viruses?

A
  1. The virus attaches to the host cell with the attachment proteins. Then they inject their nucleic acids into the host cell
  2. The genetic code of injected viral nucleic acids is read by the host cell
  3. Host cell starts to produce viral components: nucleic acids, enzymes, structural proteins
  4. These components are then assembled into new viruses
38
Q

How do cells stop dividing in healthy cell division?

A

Differentiated cells loose their ability to divide and there are genes present that can program cell death

39
Q

What is apoptosis?

A

The cell deaths that occur in healthy cell division

40
Q

What is a tumour?

A

A mass of cells that can become cancerous

41
Q

How is cancer formed from cell division?

A

Uncontrolled mitosis:
Genes that regulate cell division and cell death are mutated
Mutation passes onto daughter cells
Mutations accumulate

42
Q

Describe the arrangement of chromosomes in interphase of mitosis

A

Chromosomes (are) becoming visible/distinct

Because (still) condensing; chromosomes are condensed

Chromosomes (arranged) at random/not lined up

Because no spindle (activity);

43
Q

What does sterile mean?

A

not able to produce children

44
Q

Why would an offspring procuced be sterile?

A

Too many/extra set/three copies of chromosomes
(Homologous) chromosomes do not pair
(So) no meiosis

45
Q

Why would preventing spindle fibres forming prevent the cell cycle?

A
  1. Chromosomes/centromeres cannot attach (to spindle)
    Chromosomes cannot line up (on spindle)
  2. (So, no) metaphase
  3. Chromatids cannot separate (on spindle);
46
Q

What do you do to improve accuracy of an experiment?

A

repeats

47
Q

How is growth prevented by preventing mitosis?

A

Prevents anaphase
Disrupts formation of spindle fibres
So preventing the separation of sister chromatids
No new cells are formed

48
Q

What are evidence that chromosomes are undergoing mitosis?

A

The individual chromosomes are visible because they have condensed

Each chromosome is made up of two chromatids because DNA has replicated

The chromosomes are not arranged in homologous pairs, which they would be if it was meiosis

49
Q

How does a chromosome’s structure differ along its length?

A

Differences in base sequences

Differences in histones

Differences in condensation coiling

Biology A level (27 decks)

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