Biology 24

1.Where in a cell is the cell's DNA found?

DNA is found in the cell's nucleus.

1.Why is DNA replication necessary in a cell? Why must it be very accurate?

Because a cell contains only one copy of its DNA "program," it must make another copy before it divides so that each cell can have a copy.

2.Name five differences betwen DNA and RNA.

DNA: 1. Has the sugar, deoxyribose 2. Has nitrogen containing bases called guanine, cytosine, adenine, and thymine. 3. Found only in the nucleus 4. Only one type 5. Replicated fro DNA RNA: 1. Has the sugar, ribose 2. Has nitrogen containing bases called guanine, cytosine, adenine, and uracil. 3.Found in the nucleus, the cytoplasm, and as part of the structure of the ribosomes. 4. Three known types. 5. Transcribed for DNA

3.Briefly describe the structure of a DNA molecule.

Each DNA molecule consists of two long chains of smaller molecules that are twisted about one another called a double helix. The strands forming the "legs" of the DNA ladder consist of alternating sugar molecules and phosphate molecules. The "rungs," which connect the sugar molecules on opposite legs of the ladder, consists of a pair of nitrogen-containing bases.

2.What two scientists are credited with discovering the structure of the DNA molecule?

James D. Watson, and Francis H. C. Crick.

3.Explain the roles of DNA and the three types of RNA in protein synthesis.

Roles of DNA: Holds the DNA program, helps create all types of RNA Three types of RNA in protein synthesis: Messenger RNA - mRNA Transfer RNA - tRNA Ribosomal RNA - rRNA