unit 2 biology

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what is the first step of DNA repliaction?
DNA helicase breaks H bonds between the 2 polynucleotide DNA strands. Helix unzips to form 2 single strands
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what is the second step of DNA repliaction?
Each single strand acts as template for new strand. Free floating nucleotides join to bases on each strand by specific base pairing
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what is the third step of DNA repliaction?
Nucleotides on new strand joined together by DNA polymerase. H bonds form between original and new strand.
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what is interphase?
period of cell growth and DNA replication. Split into 3 growth stages of G1 S1 and G2
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what happens during G1?
cells grow and new organelles and proteins are made
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what happens during synthesis?
cell replicates its DNA ready to divide by mitosis
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what happens during G2?
cells keep growing and proteins needed for cell division are made
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what are the 4 stages of mitosis?
prophase, metaphase, anaphase, telophase
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what happens during prophase?
chromosomes condense getting shorter and fatter. Centrioles start moving to opposite ends of the cell, forming spindle. Nuclear envelope breaks down, chromosomes lie free in cytoplasm.
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what happens during metaphase?
chromosomes line along middle of cell, become attached to spindle by centromere
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what happens during anaphase?
centromeres divide separating each pair of sister chromatids. Spindles contract pulling chromatids to opposite ends of the cell, centromere first
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what happens during telophase?
chromatids reach opposite poles on spindle, uncoil and become long and thin again, nuclear envelope forms around each group of chromosomes, now 2 nuclei. Cytoplasm divides and there are now 2 genetically identical daughter cells
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what's cancer?
uncontrolled cell division
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describe a cancer treatment.
Some treatments are designed to interrupt the cell cycle. Target rapidly dividing cells, this kills tumour cells and some normal cells.
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what's chemotherapy?
Chemotherapy prevents the synthesis of enzymes needed for DNA replication. If these aren’t produced the cell is unable to enter the S phase, forcing the cells to kill itself
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what's radiation?
Radiation and some drugs damage DNA. When cells get to S phase it checks for damaged DNA and if it detects any it kills itself, preventing further tumour growth
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what's the process of becoming specialised?
differentiation
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what are tissues?
similar cells grouped together
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what's an organ?
group of different tissues that work together to perform a particular function
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Card 2

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what is the second step of DNA repliaction?

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Each single strand acts as template for new strand. Free floating nucleotides join to bases on each strand by specific base pairing

Card 3

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what is the third step of DNA repliaction?

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Card 4

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what is interphase?

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Card 5

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what happens during G1?

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