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Cell Division Flashcards

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1
Q

What is a homologous pair?

A

One of each pair, one from the mother and one from the father with the same genes but different alleles

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2
Q

What are sex chromosomes?

A

Determine the sex of the individual

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3
Q

What are autosomes?

A

After removing the sex chromosomes it’s the remaining chromosomes left

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4
Q

Define diploid cells

A

Body cells containing two sets of chromosomes

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5
Q

Define haploid cells

A

One set of chromosomes- gametes

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6
Q

What happens at interphase?

A
  • DNA is uncoiled and visible during interphase
  • DNA replication occurs and is checked for errors
  • Centrioles replicate in G1 and G2 in animal cells only
  • New organelles produced by mitochondria + chloroplasts
  • Cell is very active and large amounts of ATP is required
  • Protein synthesis occurs
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7
Q

What happens in prophase ?

A
  • Chromosomes become visible as they shorten and thicken
  • Centrioles move to opposite poles of the cell
  • Microtubules develop from pole to pole forming spindle fibres
  • Nucleolus disappears ( forms part of several chromosomes)
  • Nuclear envelope breaks down
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8
Q

What happens in metaphase?

A
  • Chromosomes line up at the equator of the cell
  • Centrioles reach the 2 poles
  • The spindle fibres attach to the centromere on each chromosome and pull the chromosomes to arrange them along the equator of the cell
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9
Q

What happens in anaphase?

A
  • The centromere divides
  • The chromatids are pulled apart to opposite ends of the cell
  • The spindle fibres shorten and contract , pulling the chromosomes apart , centromere leading towards opposite ends of the cell
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10
Q

What happens in telophase?

A
  • The nuclear envelope reforms around the chromosomes
  • The chromatids have now reached the poles and can be regarded as distinct chromosomes
  • Nucleolus reappears
  • The chromosomes uncoil to form chromatin
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11
Q

What is cytokinesis in animal cells?

A

This involves cell division furrowing and cleavage of cytoplasm and starts at the edge of the cell

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12
Q

What is cytokinesis in plant cells?

A

This involves cell division forming a cell plate and starts at the centre of the cell

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13
Q

Importance of mitosis

A
  • Growth in multicellular organisms- humans
  • Replacement of cells - red blood cells
  • Repair of tissues - cuts and tissues
  • Asexual reproduction
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14
Q

What are the purposes of checkpoints?

A
  • To monitor each stage of the cell cycle has been completed correctly before moving onto the next stage
  • Prevents uncontrolled division , leading to tumours
  • Detect and repair damage to DNA
  • Ensure cell is not reversed
  • DNA is only copied once during the cell cycle
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15
Q

G1 checkpoint checks for :

A
  • Cell size
  • Nutrients
  • Growth factors
  • DNA damage
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16
Q

What does the G0 phase ( resting phase ) do?

A

The cell either leaves the cell cycle permanently or temporarily
- Cell differentiation, once specialised , some cells won’t undergo mitosis again
- If damaged
- Lymphocytes: can start dividing again and re-enter the cell cycle
- Apoptosis where the cell kills themselves

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17
Q

G2 checkpoint checks for:

A
  • DNA replication ( no DNA damage)
  • Cell size
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18
Q

Spindle fibres checkpoint checks for :

A
  • Checks for chromosome attachment to the spindle fibres
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19
Q

Where does mitosis in animal cells take place ?

A

Many cells are capable of mitosis - specialised cells typically don’t go through mitosis

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20
Q

What does mitosis in plant cells take place ?

A
  • Only special regions can undergo mitosis
  • These regions are called meristems
  • Meristems cells have very thin cell walls - older cells have thicker cell walls so unable to undergo cytokinesis
  • Just behind the root tips, shoot tips , cambium , buds
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21
Q

Mitosis in yeast cells:

A
  • Reproduced by asexual reproduction/ budding
    1. The nucleus divides by mitosis
    2. cell swells on the side (bud develops)
    3. One nucleus moves into the swelling bud
    4. unequal distribution of cytoplasm
    5. 2 gentically identical cells are formed
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22
Q

Mitosis in prokaryote cells:

A
  • Occurs by a process called binary fission
    1. The cell grows to its limit
    2. DNA replicates (circular DNA)
    3. Two new loops of DNA pulled to opposite poles of the cell
    4. Cell divides into 2
    5. A new cell wall forms
    mitochandria and chloroplast dived by binary fission
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23
Q

What are stem cells?

A

undifferentiated cells which are not adapted to a particular function (unspecialised )

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24
Q

What are totipotent stem cells ?

A
  • Can differentiate into any type of cells
  • fertilised egg cells, zygote , 8-16 cells from a first few mitotic divisions
  • Produce a whole organisms
  • Differentiate into extra-embroyonic tissues like amnion/ umbilicals
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25
Q

What are pluripotent stem cells?

A
  • Stem cells that can form all tissues types but not whole organisms.
  • Present in early embroyos and the orgin of different types of tissue within an organism
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26
Q

What are multipotent stem cells?

A
  • Stem cells that can only form a range of cells with a certain type of tissue,
  • Haemtopoetic stem cells in bone marrow are mutipotent because gives rise to the various types of blood cell
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27
Q

What are unipotent stem cells?

A
  • Stem cells that only produce one cell type but have the property of self-renewal that distinguishes them from non-stem cells
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28
Q

What are erythrocytes red blood cells?

A
  • Transport of oxygen
  • Lifespan: 120 days
  • number of new cells produced from stem cell colonies - bone marrow : 3 billion per kg of body mass per day
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29
Q

What are neutrophils white blood cells?

A
  • immune system
  • Lifespan: 6 hours
  • number of new cells produced from stem cell colonies: bone marrow - 1.6 million per kg per hour
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30
Q

Sources of animal stem cells:

A

Embryonic stem cells
- Present at a very early stage of embroyo development - totipotent
- After seven days a mass of cells is called a blastocyst and the cells stay in pluripotent state and remain like this until birth
Tissue (adult) stem cells
- Present throughout life from birth
- Specific places - bone marrow
- multipotent
- can be havested from the umbilical cords of newborn babies

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31
Q

Sources of plant stem cells:

A

Meristemitic tissue ( meristems - tips of roots/ roots

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32
Q

Uses of stem cells in research and medicine:

A
  • Heart diease
  • Type 1 diabetes
  • Parkinson disease
  • Treatment of burns - produce new skin quicker
  • Drug trials - potential new drugs can be tested on stem cells
  • Spinal ijuries
  • Birth defects
33
Q

Define differentiation

A
  • When cells become specialised to perform a particular function
  • Cells can differentiate in several ways , contents of the shape can vary , different numberof organelles
34
Q

Specilised cells

Erythrocytes

A

Produced: Bone marrow
During differentiation cells lose: nucleus , mitochandria, golgi apparatus, rough ER
Contain:haemoglobin ( globular protein
Shape: Small, biconcave disc with large SA which aids in gas exchange by diffusion

35
Q

Specialised cells

Neutrophils - white blood cells

A
  • Type of phagocyte normally found in the blood stream but can squeeze out of capillaries to fight infection
    Produced: Bone marrow
    Contain: lots oy lysosomes
    Function:engulf microbes
36
Q

specialised cells

Squamous epithelial cells

A

Shape: flat, thin cells
Found - surfaces:Lining inside blood vessels - gives low friction surface for fluids
Alveoli: gives short diffusion distance for gases
Basement membrane: made of collagen + glycoproteins, secreted by the cells, attaches cells to tissues

37
Q

Specialised cells

Ciliated epithelial cells

A

Structure: column shaped cells, many mitochandria, possess cilia which waft mucus for ovum
Found: Trachea. bronchi, bronchioles, oviducts

38
Q

Specialised cells

Sperm cells

A

Shape: small, long thin shapes
undulipodium (flagellum): contains mircotubes for movement
Nucleus: contains 1 set chromosomes = haploid
Mitochandria: aerobic respiration releases to swim
Acrosome: specilised lysosome to digest outside of egg

39
Q

specialised cells

Palisade cells

A

Shape: Long, thin cells with cellulose cell walls
* Contains lots of chloroplasts (moved by cytoskeleton) for photosynthesis

40
Q

Specialised cells

Root hair cells

A

Shape: hair like projection, thin cell walls
found near tips of roots
* Increases SA
* Aids absorption of water and minerals
* Relatively large mumber of mitochandria for active transport

41
Q

Specialised cells

Guard cells

A
  • Chloroplast make sugars
  • Only epidermal cells with chloroplasts
  • CO2 can enter the leaf
42
Q

Define cells:

A
  • Smallest structural and functional unit of organism
  • Specialised to perform a specific function
43
Q

Define Tissues:

A

Collection of specialised cells working together to perform a particular function

44
Q

Define Organs:

A

Collection of tissues working together to perform a particular function

45
Q

Define organ systems:

A

Organs working together to perform a life funtion

46
Q

Tissues

Squamous epithelia

A
  • LIning tissue
  • Flattened smooth cells, lining of blood vessels, alveoli
  • Low friction, short diffusion path way
47
Q

Tissues

Cilisted epithelia

A
  • Column shaped cells
  • found in trachea, bronchi, bronchioles and oviduct
  • Cilia waft mucus of ovum in synchronished movement
48
Q

Tissues

Cartilage

A
  • Connective tissue
  • Ends of bones, ear and nose
  • Elastin and collagen
49
Q

Tissues

Muscles

A
  • Skeletal muscles contracts to move bones
50
Q

Tissues

Xylem

A
  • Thick , strong cell walls containing cellulose and ligin
  • PIts allow some lateral water movement
  • Xylem vessels are dead , no cytoplasm
  • Long continuous tube to transport water
51
Q

Tissues

Phloem

A
  • Sieve tube cells are connected o each other through sieve plates that have many pores allowing sugars to be transported
  • Sieve tube has modified cytoplasm with few organelles
  • requires energy from plant
52
Q

Organ - leaf

Cuticle

A

Waxy layer that covers the leaf and reduces water loss - not a tissue

53
Q

Organ - leaf

Upper epidermis

A
  • Usually a single layer of cells containing no chloroplasts
  • Transport and let light through the underlaying cells
54
Q

organ - leaf

Palisade mesophyll layer

A
  • Long thin tightly packed cells
  • Contains chloroplasts for photosyntheis
55
Q

Organ - leaf

Spongy mesophgyll layer

A
  • Irregular loosely packed cells with some chloroplasts
  • Air spaces allow for diffusion of gasses
56
Q

Organ - leaf

Stoma

A

Pores mainly in the lower epidermas to allow for gas exchange

57
Q

Organ - leaf

Guard cells

A
  • Two cells surrond each stoma
  • When turgid they open the pore and when flaccid they close it
  • reduces water loss
58
Q

organ - leaf

Vascular bundle

A
  • Supports the leaf as well as transporting substances
  • Xylem - water + mineral ions
  • Phloem - products of photosynthesis
59
Q

What is meiosis?

A
  • A reduction division
  • Occurs in diploid germ cells, to produce haploid cells
  • 4 genetically different cells
  • One set of chromosomes
60
Q

Meiosis

What happens in interphase? (Meiosis)

A
  • DNA replicates = consists of two sister chromatids
  • Sister chromatids contain same alleles of the same genes - gentically identical
  • Non-sister chromatids of homologous chromosomes = same genes but possible different alleles of genes
61
Q

Meiosis

What happens in propase 1(early)?

A
  • Chromosomes condense + super coil and become visible
  • Nucleolus disappers + nuclear envelope breaks down
  • Centrioles migrate to the poles + form spindle fibres which are made of microtubles
62
Q

Meiosis

What happens in prophase 1 (late)?

A
  • Homologous chromosomes pair up and form bivalents - one is paternal and the other maternal
    *Recombination occurs - the chromosomes in a bivalent may cross over at points called chiasmata where they swap section of DNA/alleles. Recombinat chromotids are formed.The genes exchange may be different alleles of the same gene resulting in gentic variation
63
Q

Meiosis

What happens in metaphase 1?

A
  • Bivalents line up randomly up the equator.
  • Independant assortment of the homologous pairs of chromosomes
  • Spindle fibres attach to them at centromeres
64
Q

Meiosis

What happens at anaphase 1?

A
  • Homologous chromosomes of each bivalent are pulled apart by spindle fibres towards poles
  • Chiasmata are pulled apart as they separate
  • Centromeres do not divide
  • Each chromosome consists of two chromotids
65
Q

Meiosis

What happens in telophase 1?

A
  • Animal cells - nuclear envelope will reform
  • Short interphases where chromosomes uncoil for a little
  • Cytokinesis may occur when cell splits
  • Most plant cells progess straight to metaphase 2
66
Q

Meiosis

What happens in prophase 2?

A
  • Happens in two nuclei
  • Chromosomes recondese - 2 chromatids each
  • Nuclear envelope disintergrates
  • Centrioles replicates
  • Spindle fibres develop vertically or perpendicular to previous division
67
Q

Meiosis

What happens in metaphase 2?

A
  • Chromosomes randonly line up at the equator
  • Independant assortment of chromotids
  • Attached to the spingle fibres at their centromeres
68
Q

Meiosis

What happens in anaphase 2?

A
  • Chromosomes are pulled apart by spindle fibres
  • Centromeres divide
  • Chromatids pulled to opposite poles
69
Q

Meiosis

What happens in telophase 2?

A
  • Chromatids reach poles and decondense
  • Nuclear envelope reforms, forming four separate nuclei
70
Q

Meiosis

What happens in cytokinesis (meiosis)?

A
  • Occurs and cells divide
  • Each cell has one set of chromosomes
  • 1 diploid cell > 4 haploid cell
71
Q

Variation

Define allele

A

Different version of the same gene

72
Q

Variation

Explain crossing over?

A
  1. When bivalents from the non sister chromatids of the homologous chromosomes are attached at point called chiasmata
  2. The chromatids can break and rejoin at the chiasmata
  3. This produces a different combination of alleles on each chromatid called recombinant chromatids
73
Q

Variation

Explain independant assortment of chromosomes?

A
  • During metaphase 1 bivalents orientate themselves randomly at the equator so the maternal and the paternal chromosomes can be facing either pole
  • Each bivalemt behaves independently
  • Any combination or maternal and paternal could end up in each gamete produced
  • 2 to the power of 23 possible combinations in animals
74
Q

Variation

Explain independant assortment of chromatids?

A
  • During metaphase 2 chromosomes orienate themselves randomly at the equator so chromatids could be facing either pole
  • Important because due to corring over the sister chromatids are no longer identical
75
Q

Variation

Explain fertilisation

A
  • Any one of about 300 Million genetically different sperm can fertilise the egg
76
Q

Variation

Explain mutation?

A
  • When DNA is replicated , a mutation could occur and lead to new alleles
77
Q

Mitosis - final notes

A
  • used in production of body cells + asexual reproduction
  • 2 daughter cell produced
  • Daughter cells have the same number of chromosomes as parent cell
  • Daughter cells contain 1 set of chromosomes
  • Diploid or haploid if parent cell was haploid
  • gentically identical unless mutation occurs
  • Diploid or haploid cells
78
Q

Meiosis - final notes

A
  • Used in production of gametes ( sperm and ova)
  • 4 daugher cells produced
  • Daughter cells have half the number of chromosomes in parent cells
  • Daughter cells contain 1 set of chromosomes
  • Daughter cells are haploid
  • Cells show genetic variation
  • Takes place in diploid germ cells
  • Meiosis has double the stages as mitosis because gametes contain 1 set of chromosomes and after meiosis it still needs to separate the chromatids pairs

Biology (13 decks)

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