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Biology OCR 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
What does it mean when chromosomes cross over
Chromosomes exchange DNA which leads to genetic variation Only happens in Prophase I
26
What happens during metaphase I of meiosis
Homologous pairs line up along the middle Independent assortment occurs
27
What is independent assortment
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
What happens in anaphase I of meiosis
Spindle fibres contract and homologous pairs are separated and pulled to either end of the cell (Sister chromatids stay together)
29
What happens in meiosis I
Cells gene is randomly divided into 2 haploid cells, introducing genetic diverstiy
30
What are the phases of meiosis
Meiosis I: Prophase I, Metaphase I, Anaphase I, Telophase I Meiosis 2: Prophase II, Metaphase II, Anaphase II, Telophase II
31
What happens in metaphase II of meiosis
Chromosomes align along the centre Independent assortment occurs
32
What happens in Anaphase II
Spindle fibres contract and pull sister chromatids by their centromeres to either end of the cell
33
What are the features of Erythrocytes
7.5um Flattened biconcave shape - for max Sa : Vol No nuclei so more space for haemoglobin Flexible - so can squeeze through narrow capillaries
34
Features of Neutrophils
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
Features of sperm cells
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
Features of palisade cells
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
Features of guard cells
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
Features of Squamous Epithelium tissue
Lining of lung Flat and thin one cell thick for rapid diffusion of O2 into blood
39
Features of Ciliated Epithelium tissue
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
Features of Cartilage tissue
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
Features of muscle tirssue
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
Features of xylem tissues
Type of Vascular tissue Composed of elongated dead cells strengthened with lignin
43
Features of phloem tissue
Composed of columns of sieve tubes, separated by perforated walls called sieve plates
44
What are stem cells
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
Totipotent definition
Able to differentiate into any cell and form an organism
46
Pluripotent definition
Can form all tissue types but cant form an organism
47
Multipotent definition
Can only form a range of cells in a certain tissue
48
Where are WBC and RBC derived from
bone marrow
49
What is the life span of RBCs and how many are produced
120 days, aprox 3 billion are produced per kg of body mass a day
50
What is the life span of WBCs and how many are produced
6 hours, aprox. 1.6 bill per kg of body mass is produced a day More during infection
51
Features of embryonic stem cells
Start off as totipotent, then a blastocyst is formed after 7 days This means that cells will be pluripotent till birth
52
What are the features of Plant stem cells
Found as meristem cells wherever growth is occurring Can be sandwiched between phloem and xylem tissue - vascular cambium
53
Where are stem cells used in medicine
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 OCR A level (23 decks)

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