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1
Q

What are the main phases of the cell cycle?

A

The cell cycle consists of interphase (which includes G1, S, and G2 phases) and mitotic phase (which includes mitosis and cytokinesis).

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2
Q

What happens during interphase?

A

Interphase is the phase where the cell grows and prepares for division. It includes G1 (cell growth), S (DNA synthesis), and G2 (preparation for mitosis).

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3
Q

What happens during mitosis?

A

Mitosis is the process of nuclear division, which consists of prophase, metaphase, anaphase, and telophase, resulting in two genetically identical daughter nuclei.

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4
Q

What is cytokinesis?

A

Cytokinesis is the process where the cytoplasm divides, resulting in two distinct daughter cells.

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5
Q

What are the stages of mitosis?

A

prophase, metaphase, anaphase, and telophase.

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6
Q

What happens during prophase in mitosis?

A

In prophase, the chromosomes condense, the nuclear envelope breaks down, and spindle fibers form.

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7
Q

What happens during metaphase in mitosis?

A

In metaphase, the chromosomes align along the metaphase plate (equator) of the cell

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8
Q

What happens during anaphase in mitosis?

A

In anaphase, the sister chromatids are pulled apart by the spindle fibers and move toward opposite poles of the cell.

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9
Q

What happens during telophase in mitosis?

A

In telophase, the chromatids reach the poles, the nuclear envelope reforms around each set of chromosomes, and the chromosomes begin to de-condense.

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10
Q

How is the cell cycle regulated?

A

The cell cycle is regulated by checkpoint proteins (such as cyclins and cyclin-dependent kinases) that ensure proper progression through the stages of the cycle. These checkpoints monitor DNA integrity and cell size.

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11
Q

What happens if a checkpoint detects an issue during the cell cycle?

A

If a checkpoint detects a problem, the cell may enter a G0 phase (resting phase), undergo repair, or undergo apoptosis (programmed cell death) if the damage is irreparable.

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12
Q

What is the difference between mitosis and meiosis?

A

Mitosis results in two genetically identical diploid cells for growth, repair, and asexual reproduction, whereas meiosis produces four genetically diverse haploid cells (gametes) for sexual reproduction.

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13
Q

What is meiosis?

A

Meiosis is a type of cell division that reduces the chromosome number by half, producing four non-identical haploid cells (gametes), which are crucial for sexual reproduction.

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14
Q

What is the main purpose of meiosis?

A

The main purpose of meiosis is to produce haploid gametes (sperm and eggs), ensuring that when fertilization occurs, the diploid chromosome number is restored.

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15
Q

What are the two main divisions in meiosis?

A

Meiosis consists of Meiosis I (reduction division) and Meiosis II (equational division), both involving prophase, metaphase, anaphase, and telophase.

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16
Q

What happens during Meiosis I?

A

During Meiosis I, homologous chromosomes are separated into two daughter cells, reducing the chromosome number by half (from diploid to haploid).

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17
Q

What happens during Meiosis II?

A

Meiosis II is similar to mitosis, where sister chromatids are separated into four genetically diverse haploid cells.

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18
Q

What happens during prophase I of meiosis?

A

In prophase I, homologous chromosomes pair up and undergo crossing over, exchanging genetic material, and forming chiasmata. This increases genetic diversity.

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19
Q

What is crossing over?

A

Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes, resulting in genetic recombination.

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20
Q

What is a bivalent and how do they occur?

A

A bivalent is what is formed when homologous chromosomes pair up.

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21
Q

What happens during metaphase 1 in meiosis?

A

Homologous pairs of chromosomes assemble along the plate.

Orientation is random and independent.

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22
Q

What’s independent assortment?

A

When the maternal or paternal chromosomes can face either end of the pole.

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23
Q

What happens in anaphase 1 of meiosis?

A

Homologous chromosomes pulled to poles and chromatids stay joined.

Entangled sections during crossing over break off and rejoin which can result in exchange of DNA.

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24
Q

What’s chiasmata?

A

The point at which chromatids break and rejoin.

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25
What causes genetic variation?
It arises from the new combination of alleles when genes are being exchanged and so sister chromatids are no longer identical.
26
What happens in telophase 1?
Chromosomes assemble at each pole and the nuclear membrane reforms. Chromosomes uncoil.
27
What happens in prophase 2?
Chromosomes condense and become visible again. Nuclear envelope breaks down Spindle formation begins
28
What happens in metaphase 2?
Individual chromosomes assemble on metaphase plate Independent assortment again and more genetic variation
29
What happens in anaphase 2 of meiosis?
Chromatids of individual chromosomes being pulled to opposite poles after division of centromeres.
30
What happens in telophase 2?
Chromatids assemble at poles. Chromosomes uncoil and form chromatin again. Nuclear envelope reforms and the nucleolus becomes visible..
31
What happens in first cytokinesis of meiosis?
Divides into two cells. Reduction of chromosome number from diploid to haploid is complete.
32
What happens in second cytokinesis of meiosis?
Division of cells forming 4 daughter cells total. Cells will be haploid due to reduction division.
33
How does meiosis II differ from mitosis?
Meiosis II is similar to mitosis, but it occurs in haploid cells, and the goal is to separate sister chromatids, not homologous chromosomes.
34
How does independent assortment increase genetic variation?
Independent assortment is the random distribution of homologous chromosomes into gametes during metaphase I, resulting in different combinations of chromosomes in each gamete.
35
What is genetic recombination?
Genetic recombination refers to the process by which new combinations of alleles are created in offspring due to crossing over and independent assortment.
36
What are recombinant chromatids?
Recombinant chromatids are chromatids that have undergone crossing over and contain a mix of genetic material from both homologous chromosomes.
37
How do crossing over and independent assortment work together to increase diversity?
Crossing over creates new allele combinations within chromosomes, while independent assortment ensures that different combinations of chromosomes are distributed to gametes.
38
What is cell specialisation?
Cell specialisation is the process by which cells become adapted for specific functions in the body, allowing them to carry out particular tasks efficiently.
39
How does cell specialisation relate to differentiation?
Differentiation is the process by which unspecialised cells become specialised to perform specific functions, resulting in different cell types within an organism.
40
What are stem cells?
Stem cells are undifferentiated cells that have the potential to become specialised into different types of cells, such as muscle, nerve, or blood cells.
41
What are some examples of specialised animal cells?
Erythrocytes, neutrophils, sperm cells.
42
What are some examples of specialised plant cells?
Palisade cells, root hair cells, guard cells.
43
What are the four main categories of tissue in animals?
Nervous tissue - adapted to support transmission of electrical impulses Epithelial tissue - adapted to cover body surfaces Muscle tissue - adapted to contract Connective tissue - adapted to to hold other tissue together or to act as transport medium
44
What is epidermis tissue adapted to do?
To cover plant surfaces
45
What is vascular tissue adapted to do?
Transport water and nutrients.
46
What is an organ?
Is a collection of tissue that are adapted to perform a particular function in an organism.
47
How many times can stem cells undergo cell division?
As many times until they become specialised which is when they enter G0
48
What is potency?
A stem cells ability to differentiate into different cell types. The greater the number of cell types it can differentiate into, the greater its potency.
49
What are the main types of stem cells?
Totipotent, Pluripotent and multipotent
50
What is totipotent?
These stem cells can differentiate into any type of cell.
51
What is pluripotent?
These stem cells can form all tissue types but not whole organisms.
52
What is multipotent?
Can only form a range of cells within a certain type of tissue.
53
How are erythrocytes specialised?
Flattened biconcave shape to increase SA:V ratio. No nucleus or many other organelles to increase space for oxygen. Are flexible to squeeze through capillaries.
54
How are neutrophils specialised?
Multi lobed nucleus - makes it easier to squeeze through small gaps to get to site of infections. Granular cytoplasm contains many lysosomes that contains enzymes used to attack pathogens
55
How are sperm cells specialised?
Have tail/flagellum - allows movement Many mitochondria - supply energy needed to swim Acrosome - located on head of sperm and contains digestive enzymes used to digest protective layers around ovum to penetrate.
56
How are palisade cells specialised?
Contain chloroplast to absorb lots of light for photosynthesis. Cells are rectangular box shapes and can be closely packed Have thin cell walls - increases rate of diffusion of CO2 Have large vacuole - maintains turgid pressure
57
How are root hair cells specialised?
Have long extensions called root hairs - increases SA of cell. This maximises uptake of water and minerals from soil.
58
How is squamous epithelium specialised?
One cell layer thick - allows for rapid diffusion.
59
How is ciliated epithelium specialised?
The cells have cilia that move in rhythmic manner. Lines trachea to waft mucus away from lungs Goblet cells produce mucus to trap unwanted particles
60
How is the epidermis specialised?
Is a single layer of closely packed cells It is covered by a waxy, waterproof cuticle to reduce water loss Has guard cells by stomata to controls gases entering and exiting
61
How are xylem tissue specialised?
Composed of elongated dead cells. Walls contain lignin to strengthen it and provide support for plants
62
What are the sources of animal stem cells?
Embryonic stem cells, tissue (adult) stem cells
63
What are embryonic stem cells
Are present at very early stage of embryo development and are toripotent. After 7 days - blastocyst is formed and cells are now in pluripotent stage Remains in this state til fetus birth.
64
What is a blastocyst?
A mass of cells
65
What are tissue stem cells?
Are present throughout life. Are multipotent. Can be stored if needed
66
What are the source/s of plant stem cells and explain?
Stem cells present in meristematic tissue. Meristematic tissue is located between phloem and xylem. The tissue is found where growth is occurring e.g at roots and shoots
67
What do stem cells have the potential of being tested in to treat?
Heart disease - muscle tissue in heart is damaged Type 1 diabetes - body’s immune system destroys insulin producing cells Parkinson’s disease - shaking and rigidity caused by death of dopamine cells in brain Alzheimer’s - brain cells are destroyed due to build up of abnormal proteins Macular degeneration- causes blindness in elderly and diabetics Birth defects Spinal injuries

Biology (19 decks)

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