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A Level Biology > Cell Division > Flashcards

Cell Division Flashcards

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1
Q

Cell cycle

A

G1
S
G2
Mitosis
Cytokinesis

{G1, S, G2 are interphase}

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2
Q

Gap 1

A
  • protein synthesis and replication of organelles
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3
Q

S phase

A
  • DNA synthesis — DNA is replicated
  • 2 sister chromatids are held together by centromere
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4
Q

Gap 2

A
  • copied DNA is checked by proof reading enzymes
  • if genes aren’t copied correctly, mutations will occur — new cells won’t work
  • organelle replication
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5
Q

What is chromatin made up of

A

DNA + histones

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6
Q

Mitosis

A

The process or nuclear division where 2 genetically identical nucleus are formed from one parent cell nucleus

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7
Q

Why is mitosis important

A
  • asexual reproduction
  • single celled organisms divide to produce 2 daughter cells that are separate organisms
  • some multicellular organisms produce offspring from parts of the parent
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8
Q

Do bacteria carry out mitosis?

A

NO
- they have no linear chromosomes, spindles or centrioles

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9
Q

Prophase

A
  • chromosomes supercoil to Horton and thicken in prophase (condense)
  • the nuclear envelope breaks down
  • centriole divides in 2 and each daughter centriole goes to pole of cell
  • spindle fibres begin to form
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10
Q

Metaphase

A
  • chromosomes line up along equator of the cell
  • spindle fibres attach to the centromeres of the chromosome
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11
Q

Anaphase

A
  • the centromere breaks - this separates the sister chromatids
  • spindle fibres shorten and pull the chromosomes apart the the poles of the cell
  • Each chromatid is identical to the original chromosome in the parent cell it was copied from
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12
Q

Telophase

A
  • new nuclear envelope forms around 2 sets of chromosomes
  • spindle fibres break down
  • supercooled chromosomes uncoil into chromatin
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13
Q

Cytokinesis

A

Mitosis is finished
- cytokinesis occurs and the cytoplasm cleaves to finally produce 2 new genetically identical daughter cells (both identical to parent cell)
- this means daughter cell can do same things the parent cell could do

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14
Q

Differences between animal and plant cell cycles

A

Animal cells
- most cells will undergo mitosis and cytokinesis
- cytokinesis starts from outside and goes in

Plant cell
- only special cells called meristem cells can divide
- plant cells do not have centrioles
- cytokinesis starts with the formation of a cell plate where the equator was- the new plasma membrane and new cell wall material is then laid down along the cell plate

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15
Q

Cytokinesis in animals, plants & fungi

A

animals- nip in along ‘cleavage furrow’
plants- along cell plate
yeast (fungi)- budding. Cell undergoes mitosis, then the cell bulges in one side, the new nucleus moves into bulge and the bulge pinched off into a new cell

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16
Q

Meiosis

A
  • 4 daughter cells (haploid)
  • genetically different
  • start from diploid cells (ovaries & testes)
  • gametes
  • 2 divisions
17
Q

Homologous chromosomes

A

Although they have the same gene, they may contain different alleles from the genes
- because one chromosome is from mum and one from dad

18
Q

Prophase 1

A
  • chromatin condenses and each chromosome supercoils
  • nuclear envelope breaks down and spindle fibres form
  • chromosomes arranged in homologous pairs (each have 2 chromatids)
  • crossing over occurs where non sister chromatids wrap around each other and may swap sections so that alleles are shuffled
19
Q

Metaphase 1

A
  • pair of homologous chromosomes still in cross over state attach along the equator of the spindles
  • each attach to the spindle by centromere
  • pairs are randomly arranged- independent assortment
  • the way they line up here determines how they will separate independently in anaphase
20
Q

Anaphase 1

A
  • chromosomes pulled apart by spindle fibres
  • centromeres do not divide, each chromosome consists of 2 chromatids
  • crossed over areas separate from each other, resulting in swapped areas of chromosomes and allele shuffling
21
Q

Telophase 1

A
  • 2 new nuclear envelopes form around each set of chromosomes, cell divides by cytokinesis
  • short interphase where chromosomes uncoil
  • each new nucleus contains half the original no. of chromosomes, but each chromosome consists of 2 chromatids

in most plant cells, the cell goes straight from anaphase 1 to prophase 2

22
Q

Prophase 2

A
  • nuclear envelope breaks down
  • chromosomes coil and condense
  • chromatids no longer identical due to crossing over in prophase 1
  • spindle fibres form
23
Q

Metaphase 2

A
  • chromosomes attach by their centromere to the equator of the spindle
  • chromatids randomly arranged
24
Q

Anaphase 2

A
  • centromeres divide
  • chromatids are pulled apart by spindle fibres towards poles
  • chromatids randomly separated
25
Q

Telophase 2

A
  • nuclear envelopes form around each if the 4 haploid cells
  • in plants, a tetras of 4 haploid cells is formed
26
Q

How meiosis produces genetic variation

A

• Crossing over during prophase 1 shuffles alleles
• Independent assortment of chromosomes in anaphase 1 leads to random distribution of chromosomes
• Independent assortment of chromatids in anaphase 2 leads to further random distribution of genetic material
• Haploid gametes are produced which can undergo random fusion with gametes from another organism of the same species

27
Q

Specialised cell

A

A cell that has become differentiated to carry out a particular function
E.g. RBC, root hair cell

28
Q

Unspecialised cell

A

Stem cells. Can develop into different types of cells
- embryonic stem cells- can develop into any type of cell
- adult stem cell- can replenish cells when needed

29
Q

Hierarchy of stem cells

A
  1. Totipotent
  2. Pluripotent
  3. Multipotent
30
Q

When stem cells have differentiated into the type of cell they will remain as, they are known as: _____

A

Terminally differentiated

31
Q

Erythrocytes

A

Function: carry O2 round the body (from lungs)

Specialisation: biconcave shape so there is a larger SA to carry oxygen
No nucleus to increase space for O2
Flexible to fit through capillaries

32
Q

Neutrophils

A

Function: destroy pathogens in the body

Specialisation: metabolic adaptations to enable them to function at low oxygen
Lobed nucleus
Granular cytoplasm contains many lysosomes containing enzymes to attack pathogens

33
Q

Squamous epithelial cells

A

Function: lines areas where diffusion takes place (alveoli and capillaries)

Specialisation: form smooth thin layer of cells in the tissue
Ideal for reducing friction
Adapted to be good at diffusion as short diffusion path

34
Q

Ciliated epithelial cells

A

Function: provides the propelling force for transport of substances

Specialisation: hair like structures (cilia), cilia are long and thin hairs to help increase surface area to project into the airways

35
Q

Sperm cell

A

Function: fertilise egg

Specialisation: flagella for movement, acrosome contains digestive enzymes to break through hard outer layer, mitochondria, haploid nucleus

36
Q

Palisade cell

A

Function: site of photosynthesis

Specialisation: lots of chloroplast, long and thin to increase SA, thin cell walls for diffusion of gases

37
Q

Root hair cell

A

Function: absorb water from soil by osmosis

Specialisation: large surface area and covered in hair like projections, no chloroplast, large vacuole

38
Q

Guard cell

A

Function: regulate opening and closing of stomata

Specialisation: strong and elastic, large vacuoles

A Level Biology (16 decks)

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