1.when does dna replication and repair occur?
2. what is the difference between hypertonic and hypotonic solutions?
3. what are the 2 types of fermenation that occur in anaerobic cellular respiration?
4. what organelle contains dna in a cell?
5.how many types of amino acids are there?
6. what are lipids? will they dissolve in water?

1.DNA polymerases are the enzymes that build DNA in cells. During DNA replication (copying), most DNA polymerases can “check their work” with each base that they add. This process is called proofreading. If the polymerase detects that a wrong (incorrectly paired) nucleotide has been added, it will remove and replace the nucleotide right away, before continuing with DNA synthesis^11start superscript, 1, end superscript.
2.When a cell is immersed into a hypertonic solution, the tendency is for water to flow out of the cell in order to balance the concentration of the solutes. Likewise, the cytosol of the cell is conversely categorized as hypotonic, opposite of the outersolution. Hypotonic refers to a lesser concentration.
3.It involves glycolysis, but not the other two stages of aerobic respiration. ... Thisoccurs when muscle cells cannot get oxygen fast enough to meet their energy needs through aerobic respiration. There are two types of fermentation: lactic acidfermentation and alcoholic fermentation.
4.nucleusEucariotic cells contain several organelles. The nucleus contains most of the DNA in a cell and this DNA is called the chromosomal DNA. It is separated from the rest of the cell (cytoplasm) by a double layer of membrane.
5.20Essential Amino Acids. Of the 20 amino acids in your body's proteins, nine are essential to your diet because your cells cannot manufacture them: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
6.Molecules that dissolve in water are "pulled apart" and "surrounded" by water molecules (hydrogen bonding). Hydrophobic molecules don't dissolve in water because they don't form hydrogen bonds.

1. DNA replication and repair occurs during the S phase (synthesis phase) of interphase.
2. In a hypertonic solution is where the concentration of solutes is greater outside the cell than inside. In a hypotonic solution, the concentration of solutes is greater inside the cell rather than the outside. 
3. Lactic acid fermentation and alcoholic fermentation
4. The nucleus
5. 20
6. Lipids are a fat used for long term energy storage, and since they are nonpolar and water is polar, they will not dissolve in water

Its either a) or b),wind and water erosion gradually widen the canyon