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Biology A level > Cell Division > Flashcards

Cell Division Flashcards

Module 1

1
Q

What is a centromere

A

It holds two chromatins together

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2
Q

What are sister chromatids

A

The two genetically identical parts of a chromosome held together at the centromere

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3
Q

What is G1 of the interphase

A

Biosynthesis
- protein synthesis
- organelles replicated
- respiration
- ATP production
- cell growth
G1 checkpoint

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4
Q

What is the G1 checkpoint

A

Checks for cell size, nutrients, growth factors and DNA damage

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5
Q

What happens during the S phase of the interphase

A

DNA replication in nucleus

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6
Q

What happens in G2 phase of the interphase

A

Proteins needed for cell division made
Energy stores are increased
G2 checkpoint

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7
Q

What is the G2 checkpoint

A

Checks for DNA damage and DNA replication completeness

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8
Q

What happens in the spindle checkpoint

A

It checks that the chromosome is attached to the spindle at the metaphase plate

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9
Q

How fast is the human cell cycle

A

23 hours

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10
Q

What is the significance of mitosis

A

For the growth and repair of an organism
For asexual reproduction

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11
Q

What are the four phases of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

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12
Q

What is cytokenisis

A

When two new cell surface membranes form and so two daughter cells form
Completes cell cycle

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13
Q

What happens at the prophase of mitosis

A

Chromosomes condense
Centrioles move to opposite ends of the cells
Spindle fibres start to form
Nuclear envelope starts to break down

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14
Q

What happens at the metaphase of mitosis

A

Chromosomes line up in the middle of the cell
Chromosomes attach to spindle by their centromere
Spindle Checkpoint

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15
Q

What happens at the Anaphase of mitosis

A

Centromeres divide, separating sister chromatids
one half is pulled to either end of the cell by the spindle contraction

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16
Q

What happens in the telophase of mitosis

A

Chromatids reach opposite ends of the cell and uncoil to become chromosomes
two nuclear envelopes form
two nuclei form

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17
Q

What is the difference between mitosis in animals and plants

A

In plants:
- only happens in meristem
- no centrioles
- Cytokinesis starts with the formation of cell plate

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18
Q

What is the importance of meiosis in organisms

A

For the production of haploid cells and genetic variation by independent assortment and crossing over

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19
Q

What are haploid cells

A

Gametes/sex cells

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20
Q

What are homologous pairs

A

Chromosomes that have been paired based on shape and size that carry the code for the same genes

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21
Q

What are alleles

A

Different versions of the same gene

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22
Q

What is meiosis

A

The process that produces gametes that are genetically different

23
Q

Differences between meiosis and mitosis

A

Mitosis:
- 2 cells produced
- 1 division
- Diploid cells produced
- Genetically identical daughter cells
Meiosis
- 4 cells produced
- 2 divisions
- haploid cells
- Genetically different daughter cells

24
Q

What happens in prophase I of meiosis

A

Chromosomes condense
Nuclear envelope disintegrates
Homologous chromosomes pair up to form bivalents
Crossing over

25
Q

What does it mean when chromosomes cross over

A

Chromosomes exchange DNA which leads to genetic variation
Only happens in Prophase I

26
Q

What happens during metaphase I of meiosis

A

Homologous pairs line up along the middle
Independent assortment occurs

27
Q

What is independent assortment

A

The idea that the orientation of each homologous pair along the equator line is random and independent
This leads to different combination of alleles, thus genetic variation occurs

28
Q

What happens in anaphase I of meiosis

A

Spindle fibres contract and homologous pairs are separated and pulled to either end of the cell
(Sister chromatids stay together)

29
Q

What happens in meiosis I

A

Cells gene is randomly divided into 2 haploid cells, introducing genetic diverstiy

30
Q

What are the phases of meiosis

A

Meiosis I:
Prophase I, Metaphase I, Anaphase I, Telophase I
Meiosis 2:
Prophase II, Metaphase II,
Anaphase II, Telophase II

31
Q

What happens in metaphase II of meiosis

A

Chromosomes align along the centre
Independent assortment occurs

32
Q

What happens in Anaphase II

A

Spindle fibres contract and pull sister chromatids by their centromeres to either end of the cell

33
Q

What are the features of Erythrocytes

A

7.5um
Flattened biconcave shape - for max Sa : Vol
No nuclei so more space for haemoglobin
Flexible - so can squeeze through narrow capillaries

34
Q

Features of Neutrophils

A

In WBC
10-14um
Has multi-lobed nucleus - so it can squeeze through gaps
Has granular cytoplasm with many lysosomes that have enzymes that attack pathogens

35
Q

Features of sperm cells

A

3um wide, 4um long
Deliver genetic info to female gametes
Have flagellum for movement
Have many mitochondria to provide energy for movement
Acrosome on head of sperm has digestive enzymes to digest protective layers around ovum to allow penetration

36
Q

Features of palisade cells

A

25-75um
in mesophyll
contain chloroplasts to absorb light for photosynthesis
Rectangular - closely packed
thin cell walls for increased rate of diffusion of CO2
Large vacuole to maintain turgor pressure
Chloroplasts can move to absorb light

37
Q

Features of guard cells

A

On surface of leaves
Has stomata so CO2 can enter for photosynthesis
Becomes less swollen when water is lost so it changes shape and closes to stop water loss
Cell wall is thicker on one side so shape doesn’t change symmetrically

38
Q

Features of Squamous Epithelium tissue

A

Lining of lung
Flat and thin
one cell thick for rapid diffusion of O2 into blood

39
Q

Features of Ciliated Epithelium tissue

A

Cells have cilia on one surface to allow it to move in a rhythmic manner
Cilia allow mucus to be swept away
Goblet cells release mucus to trap unwanted particles

40
Q

Features of Cartilage tissue

A

A connective tissue in the nose and between bones
Has elastin and collagen fibres, composed of chondrocyte cells in an extracellular matrix so its firm and flexible
prevents ends of bones from rubbing and causing damage

41
Q

Features of muscle tirssue

A

Needs to contract to cause movement
Different types like skeletal muscle
Skeletal muscle is separated by connective tissue and have microfibrils that contain contractile proteins

42
Q

Features of xylem tissues

A

Type of Vascular tissue
Composed of elongated dead cells strengthened with lignin

43
Q

Features of phloem tissue

A

Composed of columns of sieve tubes, separated by perforated walls called sieve plates

44
Q

What are stem cells

A

Undifferentiated cells that are able to undergo cell division multiple times
Once specialised they no longer divide
Can lead to tumours if not controlled

45
Q

Totipotent definition

A

Able to differentiate into any cell and form an organism

46
Q

Pluripotent definition

A

Can form all tissue types but cant form an organism

47
Q

Multipotent definition

A

Can only form a range of cells in a certain tissue

48
Q

Where are WBC and RBC derived from

A

bone marrow

49
Q

What is the life span of RBCs and how many are produced

A

120 days, aprox 3 billion are produced per kg of body mass a day

50
Q

What is the life span of WBCs and how many are produced

A

6 hours, aprox. 1.6 bill per kg of body mass is produced a day
More during infection

51
Q

Features of embryonic stem cells

A

Start off as totipotent, then a blastocyst is formed after 7 days
This means that cells will be pluripotent till birth

52
Q

What are the features of Plant stem cells

A

Found as meristem cells wherever growth is occurring
Can be sandwiched between phloem and xylem tissue - vascular cambium

53
Q

Where are stem cells used in medicine

A

Repair of damaged tissues (heart diseases, burns)
Treatment of neurological diseases (Alzheimer’s, Parkinson’s)
Developmental biology (Drug trials on stem cells instead of animals)

Biology A level (12 decks)

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