Cell Division, Cell Diversity and Cell Differentiation

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What is senescence?
When a cell can no longer divide
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What happens during the S phase?
Every molecule of DNA is replicated
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What type of proteins are produced during the G2 phase?
Proteins involved in making chromosomes condense and in spindle formation
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During the S phase, which genes are replicated first?
The 'housekeeping' genes found active in all cell types
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In which phase of the cell cycle does the cell carry out most of its metabolic processes?
G1 phase
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Why might a cell enter the G0 phase?
If it is differentiating/ specialising, if the DNA of the cell is damaged- must not be allowed to divide
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What is the name of a tumour that continues to grow and is able to spread to other parts of the body?
Malignant
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What are homologous chromosomes?
Chromosomes in a pair that are (roughly) the same size and shape and contain the same genes. However they can contain different alleles so they do not have to be identical.
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What is a gene?
The basic units which code for the order of amino acids to make a specific protein
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What is the order of the stages of mitosis?
Prophase, Metaphase, Anaphase, Telophase
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What happens during the prophase of mitosis?
Chromosomes containing two identical chromatids condense and the nuclear membrane breaks down.
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What enables the spindle fibres to move during anaphase?
motor proteins
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What does the word Meiosis mean?
Reduction
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Where are two sister chromatids joined together?
At the centromere
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In meiosis what is the main difference between anaphase 1 and 2?
Anaphase 1- homologous chromosomes are pulled to each of the poles. Anaphase 2- the chromatids of each chromosome are pulled apart
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Define independent assortment.
The random distribution of homologous chromosomes during cell division.
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In what organisms does asexual reproduction occur in?
Some plants- that produce stolons (runners), fungi, aphids, stick insects, some female sharks in captivity
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How is chromatin formed?
When DNA combines with proteins called histones
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Describe cytokinesis in animal cells.
A cleavage furrow forms around the middle of the cell. The cell suface membrane is pulled inwards by the cytoskeleton until it is close enough to fuse around the middle forming two cells.
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Describe cytokinesis in plant cells.
A new cell wall begins to form accross the centre of the cell along the line of the cell plate (middle lamella) which is made of pectin. A new cellulose cell wall is then formed on both sides of this and the membranes form inside these.
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What are plasmodesmata?
Tiny gaps/ holes in the cell wall which allow the cytoplasm of one cell to travel into its sister cell.
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What is cancer caused by?
The uncontrolled division of cells
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How can a tumour form?
If there is a spontaneous mutation of the genes that encode the checkpoint proteins which can result in cells dividing more rapidly and before the DNA has been checked.
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What is the purpose of cell cycle checkpoints?
1) to prevent uncontrolled division that would lead to tumours 2) to detect and repair damage to DNA (e.g. that caused by UV light) 3) to ensure that the cell cycle is not reversed 4) to ensure the DNA is only duplicated ONCE during each cycle.
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Why is the synthesis phase rapid?
because this is when DNA is replicated and exposed DNA are more susceptible to mutagenic antigens. Rapidness reduces the chances of spontaneous mutations occurring.
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How many Cell divisions should a cell normally undergo during its lifetime? What is this known as?
About 50. Known as the Hayflick constant
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Why is the p53 gene known as the tumour suppressor gene?
Because it triggers the two main checkpoints in the cell cycle (G1 and S checkpoints)
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Define a cell.
The smallest unit structural and functional unit of an organism.
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What is a tissue?
A group of specialised cells working together to perform a common function.
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What types of tissue is the brain made up of?
nervous tissue, blood vessels, glial tissue.
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What are glial cells?
Cells that from mylein which provides support for neurones and help to maintain homeostasis
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What is the function of the lymph system?
to transport fluid back to the circulatory system and to help resist infection
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What organs make up the endocrine system and what is its function?
Organs: glands that make hormones (thyroid, ovaries, testes, adrenals) Function: Communication, coordination and control
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What are the two main organ systems of a plant?
The shoot system and the root system
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How are palisade cells adapted for photosynthesis?
pack closely but allow air/CO2 to circulate, large vacuole to push the chloroplasts to the edge of the cell minimising the diffusion distance, many chloroplasts, cytoskeleton threads+ motor proteins move chloroplasts to upper surface when light low.
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What is meristematic tissue?
Tissue which contains the stem cells that all other plant tissues derive from
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Define an organ system.
A group of organs working together to perform an overall life function
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What organs make up the integumentary system and what is its function?
Organs: skin, hair, nails Function: Water-proofing, protection and temperature regulation
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What is the function of vascular tissue?
To carry water, minerals and sugars to the various organs of the plant
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Describe the process of crossing over.
1) chromatids of homologous chromosomes twist around one another many times 2) at certain points (chiasmata) parts of chromosomes will break off and swap with each other. Forms recombinant chromosomes-the sister chromatids will no longer be identical
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Other cards in this set

Card 2

Front

What happens during the S phase?

Back

Every molecule of DNA is replicated

Card 3

Front

What type of proteins are produced during the G2 phase?

Back

Preview of the front of card 3

Card 4

Front

During the S phase, which genes are replicated first?

Back

Preview of the front of card 4

Card 5

Front

In which phase of the cell cycle does the cell carry out most of its metabolic processes?

Back

Preview of the front of card 5
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