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Biology > - Module 2.1.6 > Flashcards

- Module 2.1.6 Flashcards

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1
Q

What is a haploid?

A

A cell with a single set of unpaired chromosomes.

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2
Q

What is a diploid cell?

A

A cell with two complete sets of chromosomes.

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3
Q

What is a gamete?

A

A sex cell (pollen/sperm/egg)

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4
Q

What is a zygote?

A

Formed when two gametes fuse together.

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5
Q

What is a mutation?

A

A change in an organism’s DNA.

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6
Q

What is mitosis?

A

Cell division that forms two identical daughter cells.

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7
Q

What is meiosis?

A

Cell division that forms 4 haploid daughter cells.

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8
Q

How do cells reproduce?

A

Cells reproduce by duplicating their contents and splitting into two daughter cells.

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9
Q

How does DNA exist in a cell?

A

It associated with specialised proteins that give it structure.
In eukaryotes these include histones.
The complex of histones and other structural proteins with DNA is called chromatin.

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10
Q

How does chromatin exist in a cell when it is decondensed?

A

Most of the time it’s decondensed, it exists in thin squiggles, can be seen under a microscope.
In this state it can be easily accessed by cellular machinery (proteins that read and copy DNA), this is important in allowing the cell to function.

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11
Q

How does chromatin exist in a cell when it is condensed?

A

It takes place when the cell is just about to divide.
When chromatin condenses you can see that eukaryotic DNA is not just one long string, instead it’s broken up into separate, linear pieces called chromosomes.

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12
Q

How many chromosomes do humans have?

A

Humans have 23 homologous pairs of chromosomes, 46 total.

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13
Q

What are features of a homologous pair of chromosomes?

A

Two chromosomes in a homologous pair are very similar, they have the same size and shape.
More importantly they carry the same type of genetic information, ie they have the same genes in the same places, but they may have different alleles.

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14
Q

What is the Hayflick constant?

A

The idea that cells should only undergo a certain number of cycles or divisions. Usually around 40-60. If this is exceeded the cell may be considered cancerous and form a tumour.

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15
Q

What is the order of the cell cycle’s processes?

A

Interphase - G1, S, G2
Nuclear division/mitosis
Cytoplasmic division/cytokinesis

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16
Q

What happens at G1 of the cell cycle?

A

The first growth phase, cells grow and increase in size.
Transcription of genes to make mRNA occurs.
Organelles duplicate
Biosynthesis - eg protein synthesis, including making the enzymes needed for DNA replication in the S phase.

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17
Q

What happens in the S (synthesis) phase of the cell cycle?

A

DNA is replicated in the nucleus.
When all chromosomes have duplicated their DNA, each one consists of a pair of identical sister chromatids.

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18
Q

What happens at G2 of the cell cycle?

A

The second growth phase.
Special chemicals ensure the cell is ready for mitosis by stimulating proteins that will be involved in making chromatin condense and in formation of the spindle.
Cells continue to increase in size.
Energy stores are increased.

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19
Q

What is G0 and what happens here?

A

G0 is a resting phase triggered by checkpoints, it is when the cell leaves the cell cycle.
Cells may undergo apoptosis, differentiation or senescence (ageing cells no longer dividing).

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20
Q

Why does G0 happen? What purpose does it have?

A

Differentiation - cells become specialised and perform this function indefinitely. It won’t enter the cell cycle again.
Damage DNA - means cells can no longer replicate, it isn’t viable.
Age - the older you are the more ‘senescent’ cells you have (linked with cancer and arthritus)

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21
Q

What is the point of checkpoints?

A

They check to see that the previous part of the cell cycle has been completed.

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22
Q

What is a cancer? How are they formed?

A

Uncontrolled cell division.
Genes mutate and become oncogenes.
Carcinogens can alter DNA to form oncogenes.

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23
Q

What are the 4 roles of mitosis?

A

DEVELOPMENT - the formation of multicellular organism from a single fertilised egg.
GROWTH - involves an increase in size through the division of cells by mitosis.
CELL REPLACEMENT - many cells within an organism are constantly dying and being replaced by mitosis.
ASEXUAL REPRODUCTION - asexual reproduction in certain plants and lower eukaryotic animals, involves the process of mitosis.

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24
Q

How do prokaryotic organisms reproduce?

A

They do not have a nucleus and they reproduce by binary fission.

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25
Q

What are the stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

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26
Q

What happens in prophase?

A

Preparation phase.
Chromatin condenses and chromosomes become visible.
In animal cells + some plant cells, two centrioles migrate to opposite poles of the cell.
Microtubules start to develop spindle shaped structures and span the cell from pole to pole.
By the end of prophase the nuclear envelope breaks down and disappears.

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27
Q

What are centrioles?

A

Cylindrical bundles of proteins that help in the formation of the spindle.

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28
Q

What happens in metaphase?

A

Middle
Microtubules from the poles are attached to the centromere.
Chromosomes are pulled along the spindle apparatus to form a plane in the center of the cell, called the metaphase plate and held in position.

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29
Q

What happens at anaphase?

A

Apart
Centromeres holding the sister chromatids divide at anaphase.
Chromatids are separated, now called chromosomes - they are pulled to opposite sides of the cell by the shortening of the spindle fibres.
Characteristic V shape as a result of the chromosomes being pulled through the cytosol.

30
Q

What happens in telophase?

A

(Two)
The sister chromatids have reached their respective poles and are now called chromosomes.
The two new sets of chromosomes assemble at each pole and the nuclear envelope reforms around them.
Spindle fibres disintegrate
Cytokinesis begins

31
Q

How does cytokinesis occur in animals?

A

Cleavage furrows form around the middle of the cell as cell membrane is pulled in by cytoskeleton until it fuses.

32
Q

How does cytokinesis occur in plants?

A

Cell wall prevents cleavage furrow. Vesicles from the golgi apparatus form along the equator where the metaphase plate was. The vesicles fuse with each other and the cell membrane, dividing the cell into two. New sections of the cell wall now form along the new sections of the membrane.

33
Q

What are the main stages of meiosis?

A

Interphase, prophase 1, metaphase 1, anaphase 1, telophase 1, prophase 2, metaphase 2, anaphase 2, telophase 2.

34
Q

What are the main features of meiosis and what does this lead to?

A

Cell division that produces gametes.
Haploid cells produced by diploid cells.
Leads to genetic variation in offspring.

35
Q

How many stages are in meiosis?

A

Meiosis is a two stage process.

36
Q

What are homologous chromosomes?

A

The set of one maternal and one paternal chromosome that pair up with each other inside a cell in meiosis.

37
Q

What happens in meiosis 1?

A

Homologous chromosomes are separated and pulled apart and placed in different cells, resulting in two haploid cells.

38
Q

What happens in meiosis 2?

A

Sister chromatids are pulled apart at the centromere and one is placed in each daughter cell, results in 4 haploid gametes.

39
Q

What happens during prophase 1? (meiosis)

A

Chromosomes condense and centrioles move to opposite ends of the cell forming a network of fibres (the spindle).
Nucleolus and nuclear envelope break down.
Homologous chromosomes pair up forming bivalents - a pair of associated homologous chromosomes.
Crossing over occurs.

40
Q

What is crossing over?

A

It results in the exchange of genetic information between maternal and paternal chromosomes.
It results new combinations of genes in the gametes.
The point of crossing over is called a chiasma.

41
Q

What happens during metaphase 1?

A

The homologous chromosomes line up along the equator of the cell.
The spindle fibres attach themselves to the centromere.
Independent assortment occurs here.

42
Q

What is independent assortment.

A

The orientation of the chromosomes when they pair up is random and independent of any other pair.
Therefore the new cells produced after meiosis 1 will have a mix of maternal and paternal chromosomes, eg they contain the same genes but not the same alleles.

43
Q

What happens during anaphase 1?

A

Spindle fibres contract and the homologous chromosomes are pulled apart to opposite poles.
Chromatids stay joined together.
Crossed over sections leads to increased variation.

44
Q

What happens during telophase 1?

A

The chromosomes reach the poles of the cells.
The nuclear envelope reforms.
Chromosomes uncoil.
Cytokinesis occurs.

45
Q

What happens during prophase 2?

A

Chromosomes condense (still two chromatids).
Centrioles migrate to opposite poles of the cell forming a network of fibres (the spindle).
Nucleolus and nuclear envelope break down.

46
Q

What happens in metaphase 2?

A

Individual chromosomes line up at the the equator of the cell.

47
Q

What happens during anaphase 2?

A

Spindle fibres contract.
Chromatids are pulled apart to opposite poles.

48
Q

What happens during telophase 2?

A

Chromatids reach the poles of the cell.
Nuclear envelope reforms.
Chromosomes uncoil.
Cytokinesis into 4 haploid daughter cells.

49
Q

What is differentiation?

A

When a new cell is formed it grows and matures and becomes specialised to carry out a particular function.

50
Q

When can animal and plant cells differentiate?

A

Animal cells usually differentiate early in their life but plant cells retain the ability to differentiate throughout their lives.

51
Q

What is a restriction of differentiation in animals?

A

In mature animal cells, division is usually limited to cell repair of tissues and cell replacement. Once cells are differentiated they can only divide and produce cells of the same type.
Some animal cells can’t divide at all once differentiated.

52
Q

True or false
All cells that originate from the zygote are genetically identical.

A

True
because they are produced by mitosis.

53
Q

How do cells differentiate?

A

Each type of cell has a specific certain combination of genes turned on and off.
Eg all human cells have the genes to produce insulin but it is only turned on in pancreas cells.

54
Q

What is the definition of a tissue?

A

A group of similar differentiated cells that have specialised functions

55
Q

What 3 types of tissues are there?

A

Nervous tissues (electrical impulses)
Epithelial tissues (cover body surfaces - internal and external)
Muscle tissues (contracts)
Connective tissues (holds tissues together or transport medium)

56
Q

What are the features of the squamous epithelium tissues?

A

They are made up of squamous epithelial cells,
One cell thick,
Present when rapid diffusion is needed (alveoli/villi)

57
Q

What are the features of the ciliated epithelium tissues?

A

Ciliated epithelial walls
Line trachea - waft mucus up to be swallowed
Associated with goblet cells

58
Q

What are the features of the cartilage tissue?

A

Connective tissue found in ear, nose and between bones.
Contains proteins elastin and collagen.
Firm and flexible

59
Q

What are the features of muscle tissue?

A

Tissues which can contract to move bones.
Skeletal muscle fibres contain myofibrils which contain contractile fibres.

60
Q

What are the features of the epidermis tissue?

A

Found on plant surfaces
Usually has a waxy cuticle to prevent water loss
Stomata

61
Q

What are the features of the xylem?

A

Vascular tissue
Responsible for water and mineral transport
Elongated, hollow cells lined with lignin

62
Q

What are the main features of phloem?

A

Vascular tissue
Transport of organic nutrients from leaves to the rest of the plant
Columns of sieve tubes which are separated by perforated sieve plates

63
Q

What is the definition of an organ system?

A

A group of organs that work together to perform a particular function.

64
Q

What are stem cells?

A

Undifferentiated cells

65
Q

What are the sources of stem cells?

A

Embryonic stem cells
Adult stem cells
Induced pluripotent stem cells made in labs

66
Q

What happens to a stem cell once they differentiate?

A

Most lose the ability to divide and enter G0

67
Q

What is a totipotent stem cell?

A

They can differentiate into any type of cell including extraembryonic stem cells (placental cells).

68
Q

What is a pluripotent stem cell?

A

Can differentiate into all cell types that make up the body but cannot form whole organisms / cannot form extraembryonic tissue

69
Q

What are multipotent stem cells?

A

They form only some types of tissue. Eg haemopoietic stem cells in bone marrow

70
Q

What are haemopoietic cells?

A

Erythrocytes and Neutrophils

71
Q

Where are plant stem cells found?

A

Meristematic tissue
Found wherever growth is occurring in plants, eg the tips of roots and shoots
Also between phloem and xylem, called the vascular cambium

72
Q

What are stem cells used for?

A

Treating burns
Drugs can be tested on tissues from stem cells before animals/humans

Biology (18 decks)

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