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Biology Year 12 > Cell Division✅ > Flashcards

Cell Division✅ Flashcards

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1
Q

Name the phases of mitosis

A

G1 interphase from 1/2 o’clock to 5/7 o’clock
S 5/8 to 9 o’clock
G2 9 to 11 o’clock
Mitosis (nuclear division) 11to 12 o’clock

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2
Q

What happens In G1 phase of mitosis

A

Organelles are synthesized and biochemicals produced, cell leaves cell cycle
G1 checkpoint checks for cell size

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3
Q

What happens during the S phase of mitosis

A

Synthesis phase- dna is replicated by semi-conservative replication

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4
Q

What happens during G2 phase of mitosis

A

Second growth phase- energy stores are increased, make new organelles, G2 checkpoint checks for dna replication

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5
Q

What phases are there during mitosis/ nuclear division phase

A

Prophase: chromosomes become visible, shorten and thicken. Spindle develops. Nuclear envelope disintegrates

Metaphase: chromosomes are arranged on the equator

Anaphase: chromosomes migrate to opposite poles

Telophase: spindle disintegrates, nuclear envelope develops

Cell divisions 1 to 2 o’clock: cell divides by construction in animal cells and cell plate formation in plants

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6
Q

What do cycling and cyclin-dependent kimases do

A

Control the checkpoints (G1 and G2)

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7
Q

State what is produced during
A: the g1 phase of interphase
B: the S phase of interphase (3 marks)

A

A: Organelles [1] (named) biochemicals [1]
B: DNA[1]

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8
Q

Explain the importance of checkpoints during cell cycle (3 marks)

A

The timing of each step in cell cycle is crucial [1] checkpoints regulate sequence of events in the cycle [1] the cycle will be halted if errors are detected [1]

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9
Q

How many daughter cells do mitosis produce and are they identical

A

2 identical daughter cells

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10
Q

Why are genetically identical cells important

A

Growth
Repair (of damaged cells)
Replacement (of cells, eg RBC, that have limited lifespans)
Asexual reproduction (in eukaryotes)

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11
Q

Describe the interphase of mitosis

A

Dna replicates, has 2 copies of all its genetic material

One chromosome, 1 chromatid (before replication)
1 chromosome, 2 chromatids (after replication)

Chromatic held by centromere

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12
Q

Describe the prophase of mitosis

A

Chromatin (comprising of DNA and histone proteins) condenses, chromosomes become visible
Nucleolus disappears
Centrioles move to the poles of the cell
Nuclear envelope break down (towards end of prophase)

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13
Q

Describe what happens during the metaphase of mitosis

A

Spindle Fibres (organized by centrioles) attach to centromeres (towards end of prophase/start of metaphase)
Chromosomes line up along the center (equator) of the cell

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14
Q

Describe what happens in the anaphase of mitosis

A

Spindle Fibres shorten
Centromeres divide
Chromatids are separated and pulled to opposite poles of the cell

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15
Q

Describe what happens during the telophase of mitosis

A

Chromatids are at the poles if the cell (can be referred to as daughter chromosome)
Nuclear envelope reform around each set of chromosomes
Chromosomes uncoil (and no longer visible)
Cell division (cytokinesis) begins

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16
Q

What happens during cytokinesis

A

Division of a cell
Begins in telophase, results in 2 genetically identical cells, each receives half of organelles and cytoplasm

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17
Q

What happens in animals and plants during cytokinesis

A

Animals: a cleavage forms (ie cell surface membrane pulled together by cytoskeleton)

Plants: cell wall prevent cleavage furrows, 2 identical daughter cells separated by new cell wall production down center of original cell

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18
Q

What is the order of stages In meiosis

A

Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2

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19
Q

What happens during prophase metaphase anaphase and telophase 1 in meiosis

A

Prophase 1: nuclear envelope disintegrates, spindles form, chromosome condense. Homologous chromosomes pair up, crossing over

Metaphase 1: homologous pairs (bivalents) line up at cell equator, independent assortment of chromosomes

Anaphase 1: homologous chromosome pairs are separated- sister chromatid both remain attached to centromeres

Telophase 1: chromosomes assemble at either pole. Cytokinesis- 2 haploid cells formed

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20
Q

What happens during meiosis II

A

Prophase 2: chromosomes condense, nuclear envelope breaks down, spindle forms

Metaphase 2: chromosomes line up at equator. Independent assortment of chromatids

Anaphase 2: random segregation of chromatids

Telophase 2: chromatids assemble at poles. Cytokinesis- 4 haploid daughter cells formed

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21
Q

In what processes and stage does genetic variation occur in meiosis

A

Crossing over: prophase 1

Independent assortment of chromosomes: metaphase 1

Independent assortment of chromatids: metaphase 2

22
Q

What happens and how do they produce genetic variation in meiosis

A

Crossing over: non-sister chromatids interweave forming bivalents, genetic material is exchanged between homologous chromosomes, producing new combinations of alleles

Independent assortment of chromosomes: when homologous chromosomes move to cell equator the alignment of each chromosome is random, when homologous chromosomes are separated in anaphase 1, many different combinations can be formed in daughter cells

Independent assortment of chromatids: chromosomes ling up at cell equator, the side on which each sister chromatid is positioned is random, sister chromatids are no longer identical, therefore many chromatid combinations are possible in daughter cells

23
Q

What are the structural features and function of red blood cells/erythrocytes

A

flattened biconcave shape-increases SA:V ratio to increases rate of O2 diffusion

No organelles- more space available for haemoglobin

Flexible due to protein arrangements in membrane- ability to squeeze through capillaries

24
Q

What are structural feature and function of neutrophils (type of white blood cell)

A

Multi-lobed nucleus- ability to squeeze through gaps in capillary walls to reach infections

Many lysosomes- contain hydrologic enzymes (to destroy pathogens)

25
Q

What are the structural features and functions of sperm cells

A

Flagellum (tail)- for movement towards the egg

Many mitochondria- to supply energy for movement

Acrosome- contain digestive enzymes to enable the sperm to penetrate the egg

26
Q

what are the structural features and functions of palisade hair cells

A

many chloroplasts (packed together)- high rate of light absorption for photosynthesis

thin cell walls- greater CO2 diffusion rate

large vacuole- to maintain turgor pressure

27
Q

what are the structural features and functions of root hair cells

A

long, narrow extension of the cell- large SA to increase water and mineral uptake from the soil

large vacuole with a higher concentration of dissolved solutes- lower water potential to increase rate of water uptake from the soil

28
Q

what are the structural features and function of guard cells

A

tow kidney shaped cells with thickened inner cell walls- they control when stomata open (depending on the requirement for gas exchange and water levels in the plant)

29
Q

where are squamos epithelium; located, structural features, function

A

capillaries and alveoli, thin/flat-increases diffusion rate

30
Q

where are ciliated epithelium; located, structural features, function

A

trachea, cilia on outisde of cells- sweep mucus from trachea

31
Q

where are cartilage; located, structural features, function

A

joints, firm and flexible- protective connective tissue

32
Q

where are skeletal muscle; located, structural features, function

A

attached to bones, contractile proteins- movement of the skeleton

33
Q

where are xylem located, structural features, function

A

plant stem, elongated dead cells strengthened by lignin- transport of water

34
Q

where are phloem; located, structural features, function

A

plant stem, perforated walls- transport of nutrients

35
Q

what is an organ

A

collection of several tissues that combine to perform a function or a range of functions

36
Q

list the organisational hierarchy

A

specialised cells-tissues-organs-organ system- whole organism

37
Q

which cells do totipotent stem cells divide into, give examples

A

any ( have potential to form a whole organism)
the first 16 cells of an animal zygote, plant meristem cells

38
Q

which cells do pluripotent stem cells divide into, give examples

A

all tissues (but not a whole organism)

early embryonic cells (in the blastocyst)

39
Q

what are the uses of stem cells

A

drug testing in vitro

studying developmental biology and disease development in vitro

treatment of burns

bone marrow transplants to replace stem cells destroyed during cancer treatment

40
Q

which cells can multipotent stem cells divide into, give examples

A

a limited range of cells

haematopoietic stem cells (in bone marrow), which can differentiate to form all blood cells, including erythrocytes and neutrophils

41
Q

what are the ethics behind pluripotent stem cells obtained from embryos

A

moral and religious reservations
scientists developing new techniques

42
Q

state what is produced during A: the G1 phase of interphase B: the S phase of interphase (3 marks)

A

A: organelles, (named biochemical)

B: DNA

43
Q

explain the importance of checkpoints during the cell cycle (3 marks)

A

the timing of each step in the cell cycle is crucial
checkpoints regulate the sequence of events in the cycle
the cycle will be halted if errors are detected

43
Q

state the number of chromatids present in a human cell A: during prophase
B: at end of cytokinesis (2 marks)

A

A: 92
B: 46

44
Q

Plants lack centrioles. What does this indicate about the role of centrioles in mitosis (2 marks)

A

centrioles are not essential for mitosis

Spindle fibres are produced through a different method in plants

45
Q

Describe the difference between A: mitosis and meiosis II
B: meiosis I and meiosis II (4 marks)

A

A:
mitosis produces diploid cells from diploid cells/ meiosis II produces haploid cells from haploid cells

genetically different daughter cells produced by meiosis II

B:
meiosis I- homologous chromosomes separated during anaphase

meiososis II- sister chromatids separated during anaphase

46
Q

explain how genetic variation is introduced to gametes during meiosis (4 marks)

A

crossing over (1)

(and) independent assortment of chromosomes/chromatids (1)

creating new combinations of alleles (1)

(independent assortment of chromatids
introduces variation because) crossing over creates genetic differences between sister chromatids (1)

47
Q

outline how sperm cells is specialised for its function (4 marks)

A

Mitochondria for ATP/ energy (1)

acrosome contains digestive enzymes for entry into egg (1)

tail/flagellum for movement (1)

protein fibres strengthen tail/flagellum (1)

48
Q

explain how presence of squamous epithelium tissue improves the efficiency of gas exchange in lungs (4 marks)

A

thin/ flattened cells (1)

present in capillaries (next to alveoli) (1)

and alveoli (1)

reduce diffusion pathway/ distance (1)

49
Q

describe one similarity and one difference between totipotent and pluripotent stem cells (2 marks)

A

both can differentiate into all cell type (1)

only totipotent cells have the potential to develop into a whole organism (1)

50
Q

explain potential benefits of using induced pluripotent stem cells rather then pluripotent embryonic stem cells for disease treatment in the future (3 marks)

A

they are obtained from adults cell (1)

overcome ethical objections to embryonic stem cell use (1)

because iPCs can be produced from cells of the patient, tissue rejection is overcome (1)

51
Q

suggest why plants are more able then animals to form reproductive clones (3 marks)

A

Mature plants have totipotent cells (1)

known as meristem cells (1)

these cells are able to differentiate into a new plant (1)

Biology Year 12 (8 decks)

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