The Cell Cycle And Dna Replication

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The Cell Cycle:

Back 1

1) The cell cycle is the process that all body cells from multicellular organisms use to grow and divide.
2) The cell cycle starts when a cell has been produced by cell division and ends with the cell dividing to produce two identical cells.
3) The cell cycle consists of a period of cell growth and DNA replication, called interphase, and a period of cell division, called mitosis.
4) Interphase is subdivided into three separate growth stages. These are called Gap Phase 1, Synthesis, and Gap Phase 2.

Front 2

DNA Replication in Interphase:

Back 2

1) The enzyme DNA helicase breaks the hydrogen bonds between the two polynucleotide DNA strands. The helix unzips to form two single strands.
2) Each original strand acts as a template for a new strand. Free-floating DNA nucleotides join to the exposed bases on each original template strand by specific base pairing.
3)The nucleotides on the new strand are joined by the enzyme DNA polymerase, and hydrogen bonds form between the bases.
4) Each new DNA molecule contains one strand from the original DNA molecule and one new strand (semi-conservative replication).

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Evidence of hereditary molecules:

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1) An experiment with mice and two kinds of pneumonia (D and N), showed there's a hereditary molecule.
2) Mice injected with strain D died, and with strain N survived.
3) Killed D was injected into mice - they survived.
4) Killed D and live N were injected together - they died.
5) Killed D had passed on an inheritance molecule to the live N strain, making it capable of causing disease.

Front 4

Evidence that DNA is the genetic material:

Back 4

1) Scientists were unsure if the hereditary molecule was DNA, RNA, or protein. They investigated it by treating the killed D strain with protease, RNase, or DNase and then injecting it along with live N strain into mice.
2) The strains that had been treated with DNase didn't kill the mice, so DNA was shown to be the hereditary molecule.