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Cell division, diversity and differentiation Flashcards

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1
Q

What are proto-oncogenes

A

-beneficial and necessary group of typical genes in a cell
-full fledged oncogenes can cause cancer

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2
Q

How is the cell cycle regulated

A

-the cell cycle has checkpoints
-the two main ones are G1/S and G2/M
-they prevent uncontrolled division that would lead to tumours
-also detect and repair damage to DNA -e.g. by UV light
-also ensure the cycle cannot be reversed and DNA is only duplicated once during each cell cycle

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3
Q

Describe the cell cycle

A

INTERPHASE (no divide; growth and synthesis)
G1 - growth of the cell. organelles are replaced, excluding chromosomes. other processes occurring - protein synthesis, respiration, photosynthesis
S - each of 46 chromosomes replicated
G2 - cell double checks the duplicated chromosomes for error, making any needed repairs and extra cell growth
M-PHASE (division)
MITOSIS- nuclear division. produces daughter cells genetic identical to each other and parent cell
CYTOKINESIS- cytoplasmic division following nuclear division, resulting in two new daughter cells. sister chromatids contain same alleles in same position

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4
Q

What is a karyotype

A

-when chromosomes lined up in order of size

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5
Q

What is apoptosis

A

cell self destructs

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6
Q

What is G0

A

-resting phase triggered during early G1 at restriction point by a checkpoint chemical
-cells may undergo apoptosis, differentiation and senescence
-some types of cells e.g neurones, remain in this phase for long time or indefinitely
-some cells do not have this phase - e.g. epithelial cells lining the gut

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7
Q

Compare mitosis in plants and animals

A

PLANTS
-only meristem (cambium) cells undergo mitosis
-no centrioles
-cytokinesis starts with formation of cell plate
ANIMALS
-most cells undergo mitosis
-have centrioles
-cytokinesis starts from outside

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8
Q

MITOSIS SIGNIFICANCE: asexual reproduction

A

-single celled protoctists such as Amoeba and Paramecium divide by mitosis to produce new individuals
-some plants reproduce asexually forming plantlets on runners
-fungi can reproduce asexually by mitosis
-asexual reproduction rare in animals; female sharks kept in captivity with no males and have reproduced genetically identical female offspring to them
-aphids may produce eggs by mitosis - don’t need fertilising

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9
Q

MITOSIS SIGNIFICANCE: growth

A

-all multicellular organisms grow by producing more cells that genetically identical to them and each other which arose by mitosis

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10
Q

MITOSIS SIGNIFICANCE: tissue repair

A

-wounds heal when growth factors, secreted by platelets and macrophages and damaged cells of blood vessel walls stimulate proliferation of endothelial and smooth muscle cells to repair damaged blood vessels

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11
Q

Describe the stages of mitosis

A
  1. PROPHASE - nuclear envelope breaks down. centriole in animal cells divides and 2 new daughter centrioles move to opposite poles of cell. cytoskeleton protein (tubulin) threads form spindle fibres between centrioles
    2.METAPHASE - pairs of chromatids attach to spindle threads at equator region. attach by their centromeres
  2. ANAPHASE - centromeres of each pair of chromatids splits. motor proteins, walking along tubulin threads pull each sister chromatid of a pair, in opposite directions, towards opposite poles. centromere goes first therefore chromosome assume a V shape
  3. TELOPHASE - separated chromosomes reach poles. new nuclear envelope forms around each set of chromosomes. cell now contains 2 nuclei each genetically identical to each other and parent cell from which they arose
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12
Q

Describe cytokinesis

A

-once mitosis is complete, cell splits into two so each new cell contains a nucleus
-in animal cells, the plasma membrane folds inwards and nips in the cytoplasm
-in plant cells an end plate forms where the equator of the spindle was, new plasma membrane and cellulose cell wall material are laid down on either side along this end plate
-two new daughter cells are now formed; they’re genetically identical to each other and to the parent cell

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13
Q

Define haploid

A

having only one set of chromosomes; represented by n

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14
Q

Define homologous chromosomes

A

-matching chromosomes, containing same genes at same places (loci)
-may contain different alleles for some of the genes

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15
Q

Define meiosis

A

-type of nuclear division that results in formation of cells containing half the number of chromosomes

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16
Q

Why is meiosis significant in life cycles

A

-sexual reproduction increases genetic variation because it involves combining genetic material from two unrelated individuals of same species by process of fertilisation
-genetic variation within population increases its chances of survival when environment changes as some individuals will have characteristics that enable them to be better adapted to change
-in many organisms, body cells are diploid
-for sexual reproduction to occur they must produce haploid gametes so when 2 gamete nuclei fuse during fertilisation, diploid zygote produced and normal chromosome number maintained through generations
-meiosis means reduction and produces haploid gametes
-diploid undergoing meiosis are in specialised organs called gonads

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17
Q

Describe homologous chromosomes

A

-46 chromosomes - 23 from mother, 23 from father
-can form matching pairs - one maternal and one maternal - called homologous chromosomes
-although have same genes, may have different alleles

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18
Q

STAGE 1 MEIOSIS: prophase one

A

-chromatin condenses and each chromosome supercoils; in this state they can take up stains and be seen with light microscope
-nuclear envelope breaks down and spindle threads of tubulin protein form centriole in animal cells
-chromosomes come together in their homologous pairs
-each member of pair consists of two chromatids
-crossing over occurs where non-sister chromatids wrap around each other and may swap sections so alleles shuffled

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19
Q

STAGE 1 MEIOSIS: Metaphase one

A

-pairs of homologous chromosomes, still in their crossed over state attach along equator of spindle by its centromere
-homologous pairs arranged randomly with members of each pair facing opposite poles
-arrangement is independent assortment - orientation of sides of chromatids random
-the way they line up in metaphase determines how they’ll segregate independently when pulled apart during anaphase

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20
Q

STAGE 1 MEIOSIS: Anaphase one

A

-members of each pair of homologous chomosomes are pulled apart by motor proteins, drag them along tubulin threads of spindle
-centromere do not divide, each chromosomes consists of two chromatids
-crossed over areas separate from each other resulting in swapped areas of chromosome and allele shuffling

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21
Q

STAGE 1 MEIOSIS: Telophase one

A

-most animal cells, two new nuclear envelopes form around each set of chromosomes and cell divides by cytokinesis
-there is then short interphase when chromosomes uncoil
-each new nucleus contains half original number of chromosomes but each chromosome consists of two chromatids
-most plant cells, the cell goes straight from anaphase one to prophase two

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22
Q

STAGE 2 MEIOSIS: prophase two

A

-if nuclear envelopes have reformed then they now break down
-chromosomes coil and condense, each one consisting of 2 chromatids
-chromatids of each chromosome are no longer identical due to crossing over in prophase one
-spindles form

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23
Q

STAGE 2 MEIOSIS: metaphase two

A

-chromosomes attach by centromere to equator of spindle
-chromatids of each chromosome are randomly arranged (independent assortment)
-the way they are arranged will determine how chromatids separate during anaphase

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24
Q

STAGE 2 MEIOSIS: anaphase two

A

-centromere divides
-chromatids of each chromosome are pulled apart by motor proteins that drag them along the tubulin threads of spindle towards opposite poles
-chromatids are therefore randomly segregated

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25
Q

STAGE 2 MEIOSIS: telophase two

A

-nuclear envelopes form around each of 4 haploid nuclei
-in plants a tetrad of 4 haploid cells is formed

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26
Q

How does meiosis produce genetic variation

A

-crossing over during prophase 1 shuffles alleles
-independent assortment of chromosomes in anaphase 1 leads to random distribution of maternal and paternal chromosomes of each pair
-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 derived from another organism of same species

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27
Q

How can embryonic cells differentiate

A

-differentiation is the process by which stem cells become specialised into different types of cells
-certain genes are switched off and some expressed more so that
-proportions different organelles differs from others
-shape cell changes
-some contents of cell changes
-each cell type specialised for particular function

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28
Q

ANIMAL: erythrocyte adaptations

A

-carry oxygen form lungs to respiring cells
-very small, 7.5um diameter - large SA/V ratio, helped by bioncave shape - means oxygen can easily diffuse across membranes
-flexible to travel through narrow capillary
-most organelles lost and little cytoplasm provides space for more haemoglobin molecules

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29
Q

ANIMAL: neutrophils

A

-attracted to and travel towards infection site by chemotaxis
-function to ingest bacteria and some fungi by phagocytosis

30
Q

ANIMAL: spermatozoa

A

-many mitochondria carry out aerobic respiration - ATP provides energy for undulipodium to propel cell towards ovum
-small but long and thin, they can move easily
-once reaches ovum, enzymes released from acrosome - digest outer protective covering ovum, allow sperm to enter
-head contains haploid male gamete nucleus

31
Q

ANIMAL: epithelial cells

A

-epithelium is lining tissue- found outside and inside
-squamous epithelial cells are flattened in shape
-have many cilia

32
Q

PLANT: palisade cells

A

-closely packed photosynthetic cells
-long and cylindrical, pack together closely with little space between
-larger vacuole so chloroplast positioned near periphery of cell. reducing diffusion distance for CO2
-contain many chloroplasts -organelles that carry out photosynthesis
-have cytoskeleton threads and motor proteins to move chloroplasts

33
Q

PLANT: guard cells

A

-in leaf epidermis, cells that surround stomata
-light energy used to produce ATP
-ATP actively transports potassium ions from surrounding epidermal cells into guard cells lowering water potential
-water enters guard cells via osmosis
-guard cells swell - the tips bulge and stoma enlarge
-stomata open, air can enter spaces beneath palisade cells
-gaseous exchange can occur, CO2 diffuse into palisade cells - use it for photosynthesis and maintain steep concentration gradient
-oxygen produced during photosynthesis can diffuse out of palisade cells into air spaces and out through open stomata

34
Q

PLANT: root hair cells

A

-hair like projection in epidermal cells increase surface area for absorption water and minerals
-mineral ions actively transported into root hair cells lowering water potential, causing water to follow in by osmosis
-have special carrier proteins for active transport
-produce ATP needed for active transport
-root cap, protecting root tip, continuously replaced

35
Q

ANIMAL: epithelial tissue

A

-covers and lines free surfaces in body such as skin, cavities of digestive and respiratory system, blood vessels etc
-epithelial tissue made up almost entirely of cells
-cells very close to each other and form continuous sheets
-adjacent cells are bound together by lateral contacts
-no blood vessels within epithelial tissue; cells receive nutrients by diffusion from tissue fluid in underlying connective tissue
-some epithelial cells have smooth surfaces but some have projections, either cilia or microvilli
-epithelial cells have short cell cycles and divide up two or three times a day to replace worn or damaged tissue
-epithelial tissue specialised to carry out its functions of projection, absorption, filtration, excretions and secretion

36
Q

ANIMAL: connective tissue

A

-connective tissue widely distributed in body
-consists of non living extracellular matrix containing proteins (collagen and elastin) and polysaccharides
-this matrix separates living cells within tissues and enables it to withstand forces such as weight
-blood, bone, cartilage, tendons, ligaments and skin are connective tissue

37
Q

ANIMAL: cartilage

A

-hyaline cartilage forms the embryonic skeleton, covers ends of long bones in adults, joins ribs to sternum and is found in nose, trachea and larynx
-fibrous cartilage occurs in discs between vertebrae in backbone and in knee joint
-elastic cartilage makes up outer ear and epiglottis

38
Q

ANIMAL: muscle tissue

A

-well vascularised (has many blood vessels)
-muscle cells called fibres; they are elongated and contain special organelles called myofilaments made of actin and myosin
-these allow muscle tissue to contract

39
Q

What are the functions of muscle

A

-skeletal muscles packaged by connective tissue sheets, joined to bones by tendons; these muscles contract to cause bones to move
-cardiac muscle makes up walls of heart and allows heart to beat and pump blood
-smooth muscle occurs in walls of intestine, blood vessel, uterus and urinary tracts and it propels substances along these tracts

40
Q

PLANT: epidermal tissue

A

-consists of flattened cells that lack chloroplasts and form protective covering over leaves, stems and roots
-some epidermal cells have walls impregnated with waxy cuticle
-this is important for plants that live in dry areas as cuticle reduces water loss

41
Q

PLANT: vascular tissue

A

-xylem vessels carry water and minerals from roots to all part of plant
-phloem sieve tubes transfer the products of photosynthesis (mainly sucrose sugar) in solution from leaves to parts of plant that do no photosynthesise such as roots, flowers and growing shoots

42
Q

PLANT: meristematic tissue

A

-meristematic tissue contains stem cells
-have thin walls containing very little cellulose
-do not have large vacuoles
-do not have chloroplasts
-can divide by mitosis and differentiate into other types of cells

43
Q

How do xylem and phloem derive from meristems

A

-some cambium cells differentiate into xylem vessels
-lignin is deposited in their cell wall to reinforce and waterproof them however also kills the cells
-ends of cells break down so xylem forms continuous columns with wide lumens to carry water and dissolved minerals
-other cambium cells differentiate into phloem sieve tubes or companion cells
-sieve tubes lose most of their organelles and sieve plates develop between them
-companion cells retain their organelles and continue metabolic functions to provide ATP for active loading of sugars into sieve plates

44
Q

PLANT ORGAN FUNCTIONS: leaf, root, stem, flower

A

-LEAF - photosynthesis
-ROOT- anchorage in soil, absorption of mineral ions and water, storage
-STEM- support, holds leaves to sunlight, transportation of water, minerals and products of photosynthesis, storage of products of photosynthesis
-FLOWER- sexual reproduction

45
Q

What are stem cells

A

-undifferentiated cells, capable of becoming any type of cell
-described as pluripotent
-able to express all genes
-can divide by mitosis and provide more cells that can then differentiate into specialised cells for growth and tissue repair

46
Q

Sources of stem cells

A

-adult stem cells - found in developed tissues, such as brain, muscle, skin, amongst undifferentiated cells; act like repair system because renewing source undifferentiated cells
-embryonic - present in early embryo, formed when zygote begins to divide
-stem cells in umbilical cord blood
-induced pluripotent stem cells (iPS) - developed in labs by reprogramming differentiated cells to switch on certain key genes and become undifferentiated

47
Q

POTENTIAL MEDICINE: bone-marrow transplant

A

-stem cells from bone marrow extensively used in bone marrow transplants to treat diseases of the blood (e.g. sickle cell anaemia and leukaemia) and immune system(e.g. SCID)
-also used to restore patients blood system after treatment for specific types of cancer where patients bone marrow cells can be obtained before treatment, stored and put back inside afterwards

48
Q

POTENTIAL MEDICINE: drug research

A

-if stem cells can be made to develop into particular types of human tissue, then new drugs can be tested first on these tissues rather than animal tissues

49
Q

POTENTIAL MEDICINE: developmental biology

A

-stem cells can be used to research developmental biology and enable a better understanding of how multicellular organisms develop, grow and mature
-can study how stem cells develop to make particular cell types and learn how each cell types functions to see what goes wrong when diseases
-they’re trying to find out if they can expand capacity embryos have for growth and tissue repair into later life

50
Q

How do stem cells repair damaged tissues (regenerative medicine)

A

-stem cells been used to treat mice with type 1 diabetes by programming iPS cells to become pancreatic beta cells. Research under way for such treatment of human diabetes
-bone marrow stem cells can be made to develop into liver cells and could be used to treat liver disease
-stem cells directed to become nerve tissue used to treat Alzheimer and Parkinson diseases or repair spinal cord injuries
-stem cells may be used to populate bioscaffold of organ, then directed to grow specific organ for transplanting

51
Q

Potentials of regenerative medicine

A

-if can make organ, no need for immunosuppressant drugs
-may eventually treat arthritis, strokes, burns, heart disease etc

52
Q

Define pluripotent, multipotent, totipotent

A

-PLURIPOTENT- can differentiate into most cell types
-MULTIPOTENT- can differentiate into many cell types
-TOTIPOTENT - can differentiate into ALL cell types

53
Q

STRUCTURE: fibrous cartilage

A

-densely layered collagen fibres and mix of fibrous tissue
-acts as cushion to absorb shocks
-found on ends of bones

54
Q

STRUCTURE: elastic cartilage

A

-firm but flexible tissue
-found in nose and ears
-made of chondrocyte cells
-together in elastic fibres
-hold structure but allow flexibility for protection

55
Q

STRUCTURE: nervous tissue

A

-found in brain, spinal cord, nerves
-stimulates muscle contraction
-actual nerve cell is neurone - transmits impulses
-other cell is neuroglia
-located in CNS and PNS
-sensory neurone: convert signals from external environment
-myelin sheath protect axon
-ATP needed for transmitter therefore have mitochondria

56
Q

STRUCTURE: flower organ

A

-allow for reproduction of plants
-petals attract insects
-rely on pollinators or wind to carry pollen from one flower to another
-sepal protect interior of flower
-stamen in male reproductive organ of flower and holds plant towards pollinator
-ovule contains developing seeds

57
Q

STRUCTURE: xylem elements and tracheids

A

-xylem found within vascular bindle to transport water and minerals
-made up of xylem elements and strengthened by lignin
-dead, hollow cells make up a tube connected end to end

58
Q

STRUCTURE: sclerenchyma and parenchyma

A

-sclerenchyma - specialised plant tissue, tough and fibrous for support
-parenchyma- unspecialised, used for structure and support, actively involved in photosynthesis, found in cortex, pith etc
-can divide to heal wounds on surface of plant

59
Q

STRUCTUR: guard and root hair cells

A

-root - allow plant to absorb more water and minerals
-have mitochondria for ATP doe movement NO3-
-long hair like projections increase surface area for absorption
-guard - surround stomata, open stomata when turgid as potassium ions pumped in
-allow for gaseous exchange

60
Q

STRUCTURE: phloem vessels

A

-type of vascular tissue allow movement of assimilates via translocation
-primary growth makes plant grow horizontally
-secondary growth in woody plants
-parenchyma, sclerenchyma for support
-sieve tube elements have little cytoplasm

61
Q

STRUCTURE: leaf organ

A

-leaf is an organ
-transport glucose and water so can carry out photosynthesis
-petiole and stalk
-large surface area, thin, waxy cuticle

62
Q

STRUCTURE: collenchyma and chlorenchyma

A

-collenchyma - elongated living cells, uneven thick walls, provide strength, support and protections
-chlorenchyma- fatty acids, lipids, rows of tissue, stores chlorophyll

63
Q

STRUCTURE: spermatozoa

A

-male sex cell that carries genetic material
-enable sexual reproduction
-oval head, long undulipodium (9+2 microtubules)
-mitochondria produce ATP for energy
-head carries chromosomes
-acrosome contains digestive enzymes to fertilise egg

64
Q

STRUCTURE: bone tissue

A

-gives basic structure
-locomotion - movement of body
-mineral ion storage
-harbouring of bone marrow, contain stem cells
-compact bone, more dense
-spongy bone, less dense
-change overtime- functional adaptation

65
Q

STRUCTURE: blood

A

-classified as liquid tissue
-made up of RBS, plasma, WBC
-haemoglobin enables oxygen to be carried
-7.5-8.7um
-small and narrow, bioncave disk
-WBC - protect body from pathogens
-plasma carry nutrients, proteins and hormones

66
Q

STRUCTURE: palisade mesophyll

A

-found in upper parts of leaf to increase light absorption
-where most photosynthesis occurs
-cylindrical shape allows to be closely packed together
-lots of chloroplasts to maximise light absorption
-chloroplasts move by motor proteins
-thin cell wall to reduce diffusion distance

67
Q

STRUCTURE: erythrocyte and neutrophil

A

-erythrocyte - carry haemoglobin, 7-8um, bioncave disk, begin in bone marrow, able to bind to 4 oxygen molecules
-neutrophil - target unknown bacteria, 10-12 um, most common WBC and part of leucocytes, granular cytoplasm

68
Q

STRUCTURE: tap roots

A

-tap root systems have dominant primary root which grow vertically into soil; smaller lateral roots arise
-large primary root can reach deep into soil to absorb more water and store food; help plant survive drought and seasonal changes

69
Q

STRUCTURE: fibrous roots

A

-located closer to surface of soil, form dense network of roots - help prevent soil erosion
-typically found in areas where water supplies abundant

70
Q

STRUCTURE: monocot

A

-do not have vascular cambium as growth will not be lateral
-do not have cortex and pith but concentration bands of sclerenchyma cells, gives stem flexibility and strength to withstand changes

71
Q

STRUCTURE: dicot

A

-have epidermis covered by waxy cuticle - prevents water loss and stops inner tissues from drying out
-collenchyma have unevenly thickened walls; areas where cell wall thicker, stem strengthened for support, where wall thinner, flexibility to cope with wind
-parenchyma cells make up bulk of cortex - cells are thin walled and there are intracellular spaces which important for gaseous exchange

72
Q

STRUCTURE: hard stems

A

-woody plants have hard stems, allowing them to survive above ground in winter
-have secondary growth which allow plant to increase in thickness
-also, secondary vascular tissue added as plant grows, as well as cork layer

Biology (13 decks)

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