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Bases that are purines..
Adenine (A) and Guanine (G)
Bases that are pyrimidines..
Thymine (T) and Cytosine (C)
Replication of DNA:
- 1. Before replication, parental DNA are hydrogen-bonded to one another
- 2. The enzyme DNA helicase unwinds and "unzips" the double stranded DNA
- 3. New complementary DNA nucleotides, always present in nucleus, fit into place by the process of complementary base pairing. These are positioned and joined by the enzyme DNA polymerase.
- 4. To complete replication, the enzyme DNA ligase seals any breaks in the sugar-phosphate backbone.
- 5. The two double helix molecules are identical to each other and to the original DNA molecule.
RNA (ribonucleic acid)
- - Is a polynucleotide (fjölkirni)
- - Contains the sugar ribose
- - Contains the bases: A,C,G,U
- - mRNA, rRNA, and tRNA
Messenger RNA (mRNA)
Takes a message from DNA to the ribosomes. (In eukaryotic cells DNA is in the nucleus, and the ribosomes are in the cytoplasm).
Ribosomal RNA (rRNA)
rRNA, along with proteins, makes up the ribosomes, where proteins are synthesized.
Transfer RNA (tRNA)
tRNA transfers amino acids to the ribosomes.
Transcription (of DNA to form mRNA)..
During transcription, the enzyme RNA polymerase copies a strand of the DNA into a complementary RNA molecule. In eukaryotic cells, the primary mRNA molecule is processed by modification of the 5' and 3' and removals of the introns. The mature mRNA leaves the nucleus.
AUG - methionine