Highlights Recombinant DNA II

1. DNA is the genetic material. In order for cells to divide, DNA must be replicated first.

2. Replication of DNA requires catalysis by DNA Polymerase.

3. In order for cells to make protein, they must convert information in the sequence of nucleotides in DNA ultimately into the sequence of amino acids in proteins.

4. Different proteins have different amino acid sequences. Changing the amino acid sequence of a protein changes the protein's shape as well as its properties.

5. Before information in DNA can be used to make proteins, it must first be converted into RNA.

6. Synthesis of RNA from DNA is called transcription and it occurs in the nucleus of eukaryotic cells. Synthesis of protein from RNA is called translation and it occurs in the cytoplasm of eukaryotic cells.

7. Synthesis of RNA from DNA is catalyzed by an RNA Polymerase.

8. There are three main types of RNA, called messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

9. mRNA carries the "message" from the DNA in the form of the genetic code to the ribosomes for making protein.

10. rRNAs are components of ribosomes. rRNAs catalyze the formation of peptide bonds between amino acids in proteins. rRNAs are examples of catalytic RNAs and we call catalytic RNAs 'ribozymes'

11. tRNAs are cloverleaf-like structures. At one end (a 'leaf') resides a three base sequence called the 'anti-codon'. The anti-codon of the tRNA pairs with the codon of the mRNA in the middle of the ribosome. At the other end of the tRNA is a specific amino acid. Each anti-codon has a specific amino acid associated with it.

12. Amino acids get attached to tRNAs by action of enzymes called aminoacyl-tRNA synthetases. You can call them AATS. There is one AATS for each amino acid and there are 20 amino acids.

13. Ribosomes are protein/rRNA complexes that look like inverted snowmen. They contain a larg subunit and a small subunit. Between the two sucunits slides the mRNA during the process of translation.

14. The genetic code is the information converting DNA sequence to amino acid sequence. The three base codons of mRNA each pair with one anti-codon of the tRNA, which brings in one specific amino acid to the translation process. The genetic code is universal, meaning that same three bases specify the same amino acid in all cells.

15. The overall processes of DNA replication, transcription and translation are basically the same in prokaryotic and eukaryotic cells. There are some notable differences in location, though. Prokaryotic cells do not have a nucleus to separate things out, so DNA replication, transcription, and translation all occur at the same place. Transcription and translation frequently occur simultaneously in prokaryotic cells.

16. In eukaryotic cells, DNA replication and transcription occur in the cytoplasm, but translation occurs in the cytoplasm. Thus, transcription and translation can't occur simultaneously in eukaryotic cells.

17. One other major difference between eukyarotic and prokaryotic cells is that the RNAs in eukaryotic cells are "spliced", meaning interior pieces of them are removed and the remaining ends are joined together. Splicing does not occur in prokaryotic cells.