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A level Biology > Chapter 6 - Cell Division > Flashcards

Chapter 6 - Cell Division Flashcards

1
Q

What are the main phases of the cell cycle?

A

Interphase
Mitotic phase

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2
Q

What is interphase?

A

Cell spends most of the time in this phase
Not actively dividing
Preparing for cell division

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3
Q

What are the three stages of interphase and what happens in them?

A

G1 - first growth phase, organelles replicate and cell increases in size
S - synthesis phase, DNA is replicated in the nucleus
G2 - second growth phase, cell continues to increase in size, energy stores are increased and duplicated DNA is checked for errors

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4
Q

What is the mitotic phase?

A

Period of cell division
Mitosis - nucleus divides
Cytokinesis - cytoplasm divides and two cells are produced

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5
Q

What is G0 and why does it happen?

A

When cell leaves the cell cycle - temporarily or permanently
Differentiation - specialises then is no longer able to divide
DNA of cell is damaged so can longer divide
Diseases such as arthritis or cancer

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6
Q

How is the cell cycle controlled?

A

Checkpoints - control mechanisms of the cell cycle, monitor and confirm that processes have been successfully completed before moving onto the next stage

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7
Q

What happens that the G1 checkpoint?

A

End of G1 phase
Checks for cell size, nutrients, growth factors and DNA damage
If it isn’t completed it will enter G0

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8
Q

What happens at G2 checkpoint?

A

End of G2 phase
Checks for cell size, DNA replication and DNA damage
If completed the cell initiates the process for mitosis

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9
Q

What happens at the spindle assembly checkpoint?

A

All chromosomes should be attached to spindles and have aligned during metaphase
Mitosis cannot proceed unless it is complete

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10
Q

What is mitosis?

A

Process of the nucleus splitting to produce 2 genetically identical nuclei in order to produce two genetically identical daughter cells in cytokinesis

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11
Q

What are the four stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

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12
Q

What is the process of prophase?
(mitosis)

A

Chromatin fibres coil and condense
Nucleolus disappears
Nuclear membrane breaks down
Centrioles migrate to opposite poles
Spindle fibres attach to centromeres and start moving chromosomes to the center
Nuclear envelope disappears

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13
Q

What is the process of metaphase?
(mitosis)

A

Chromosomes are pulled by the spindle fibres to form a plane in the center of the cell called the metaphase plate

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14
Q

What is the process of anaphase?
(mitosis)

A

Centromeres divide
Chromatids are separated and pulled to opposite poles by the shortening of spindle fibres

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15
Q

What is the process of telophase?
(mitosis)

A

Chromatids reach the poles (and are now called chromosomes)
Nuclear envelope reforms around the two new sets of chromosomes
Chromosomes uncoil and nucleolus is formed

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16
Q

What is the process of cytokinesis in animal cells?

A

Forms a cleavage furrow around the middle of the cell
The cell surface membrane is pulled inwards by the cytoskeleton until it is close enough to form around the middle forming two cells

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17
Q

What is the process of cytokinesis in plant cells?

A

No cleavage furrow forms due to it having a cell wall
Vesicles from the golgi apparatus begin to assemble in the same place as the metaphase plate was formed and the vesicles fuse to each other and the cell surface membrane dividing the cell into two
New sections of the cell wall form along the new membrane

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18
Q

What is a diploid cell?

A

A cell with two chromosomes of each type
One from the mother one from the father

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19
Q

What is a haploid cell?

A

A cell with one chromosome of each type
e.g. gamete

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20
Q

What are homologous chromosomes?

A

Chromosomes with the same genes at the same loci
They are not the same chromosomes as they have one from each parent

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21
Q

What is an allele?

A

Different versions of the same gene (gene variants)

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22
Q

What are the two phases of meiosis?

A

Meiosis 1
Meiosis 2

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23
Q

What happens in meiosis 1?

A

Pairs of homologous chromosomes are separated
Each cell will only contain one full set of genes instead of two so the cells are haploid

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24
Q

What happens in meiosis 2?

A

Pairs of chromatids are separated
Produces four haploid daughter cells

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25
What is the process of prophase 1? (meiosis)
Chromosomes condense Nuclear envelope disintegrates Nucleolus disappears Spindle formation begins Homologous chromosomes pair up forming bivalents Chromosomes do crossing over
26
What is the process of metaphase 1? (meiosis)
Same as metaphase in mitosis but instead homologous pairs of chromosomes assemble along the metaphase plate Orientation of each homologous pairs are random
27
What is the process of anaphase 1? (meiosis)
Bivalents are pulled to opposite sides and chromosomes stay joined together Chiasmata - point at which chromatids break and rejoin during crossing over Exchange forms recombinant chromatids which leads to genetic variation
28
What is the process of telophase 1? (meiosis)
Same as mitosis telophase Chromosomes assemble at each pole and the nuclear membrane reforms Chromosomes uncoil Cell undergoes cytokinesis and divides into two haploid cells
29
What is the process of prophase 2? (meiosis)
Chromosomes condense Nuclear envelope breaks down Spindle formation starts again
30
What is the process of metaphase 2? (meiosis)
Individual chromosomes assemble on the metaphase plate
31
What is the process of anaphase 2? (meiosis)
Chromatids of a chromosome are pulled apart to opposite poles after division of centromeres
32
What is the process of telophase 2? (meiosis)
Chromatids assemble at the poles Chromosomes uncoil Nuclear envelope reforms Nucleolus becomes visible Cytokinesis results in four haploid daughter cells
33
What is meiosis?
Production of gametes for sexual reproduction Produces variation
34
What is the process of crossing over?
Swapping of genes at a point called the chiasma This creates variation Only happens in prophase 1
35
What is independent segregation of chromosomes?
Chromosomes align on the metaphase plate randomly and one from each pair goes into a daughter cell In metaphase 1 and 2
36
How can genetic variation be created?
Independent segregation of chromosomes Crossing over Mutations Random sperm reaching random egg
37
What is a cell?
Smallest unit of a living thing Differentiated meaning it is specialised to carry out a specific function
38
What is a tissue?
A collection of the same differentiated cells that have a specialised function
39
What is an organ?
A collection of different tissues adapted to perform a specific function
40
What is an organ system?
Composed of a number of organs working together to carry out a major function in the organism
41
What is the levels of organisation in multicellular organisms? (smallest to biggest)
Cells Tissues Organs Organ systems Organism
42
What is an erythrocyte?
Animal cell Red blood cell Flattened biconcave shape - Increased surface area to volume ratio No nucleus - space for haemoglobin Transport Oxygen around body Flexible - to fit through narrow capillaries
43
What is a neutrophilis?
Animal cell White blood cell Multi-lobed nucleus - easier to squeeze through gaps to get to the site of infection Granular cytoplasm - contains lysosomes with enzymes to attack pathogens
44
What is a sperm cell?
Animal cell Gamete Delivers genetic information to the ovum (egg cell) Flagellum for movement Lots of mitochondria for energy to swim to the egg Acrosome on the head contains digestive enzymes to break protective layer around the ovum
45
What are palisade cells?
Plant cell Present in mesophyll Lots of chloroplasts to absorb light, can move to absorb more light Thin cell walls - increases diffusion rate of carbon dioxide Large vacuole - maintain turgor pressure
46
What are root hair cells?
Plant cell Present at growing tips of roots Hairs increase surface area of cell which maximises uptake of water
47
What are guard cells?
Plant cell Pairs of guard cells form stomata - necessary for carbon dioxide to enter plants for photosynthesis When guard cells lose water they become less swollen, they change shape and the stomata closes
48
What is the squamous epithelium?
Animal tissue Specialised squamous epithelium cells Very thin - one cell thick Lining of the lungs
49
What is the ciliated epithelium?
Animal tissue Cilia on the surface Lines trachea Contains goblet cells - secrete mucus
50
What is cartilage?
Animal tissue Connective tissue Fibres of elastin and collagen Chondrocyte cells embedded in the extracellular matrix
51
What is muscle?
Animal tissue Can contract Has fibres Contain myofibrils Contain contractile proteins
52
What is the epidermis?
Plant tissue Closely packed cells on plants Waxy and waterproof Has stomata
53
What is the xylem tissue?
Plant tissue Vascular tissue Transports water and minerals Made up of dead cells Strengthened by lignin
54
What is the phloem tissue?
Vascular tissue Transport of organic nutrients such as sugar Columns of sieve tubes - separated by sieve plates
55
What are stem cells?
Undifferentiated cells that undergo cell division again and again as necessary Needed for growth and development Become specialised by differentiation Once a stem cell becomes differentiated it can no longer undergo cell division
56
What is potency?
A cells ability to differentiate into different types of cell
57
What is a totipotent stem cell?
Can differentiate into any type of cell Only found in zygote in its first 8 or 16 cells which can form the whole organism
58
What is a pluripotent stem cell?
Form all kinds of tissues but not whole organisms e.g. early embryos (embryonic stem cells)
59
What is a multipotent stem cell?
Can differentiate into a limited range of cells e.g. hematopoietic stem cells in the bone marrow can differentiate into various blood cells
60
Why is it important for erythrocytes to be renewed so often?
No nucleus or membrane bound organelles so have a lifespan of 120 days
61
Why is it important for neutrophils to be renewed so often?
Important role in the immune system Have a lifespan of 6 hours Can only engulf a few pathogens before dying
62
Why is it important for multicellular organisms to have specialised cell?
To take on different roles in tissues and organs To meet the high metabolic demands
63
Where can animal stem cells be sourced from?
Embryonic - can be extracted from a zygote Adult - bone marrow or umbilical cord
64
Where can plant stem cells be sourced from?
Meristems - found at root tips and shoots or in between the phloem and xylem
65
What can stem cells be used for?
Heart disease Type 1 diabetes Parkinson's disease Alzheimer's disease Macular degeneration (blindness) Birth defects Spinal injuries Treatment of burns Drug trials
66
What are the ethical issues around using embryonic stem cells?
Removal of stem cells from embryos often results in destruction Religious and moral objections - belief that life begins at conception Lack of consensus - when does the baby have right to consent to this treatment and who does the genetic material used for research belong to

A level Biology (24 decks)

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