1. While replication, one strand will form a continuous copy while the other form a series of short “Okazaki” fragments • Genetic traits can be transferred from one organism to another using operation similar to cut and paste or scissor and glue operation • Information flow is from DNA to RNA via the process of transcription, and then to protein via translation • Transcription is the making of an RNA molecule from DNA template • Translation is the construction of an amino acid sequence (polypeptide) from an RNA molecule

2. PCR

3. Transcription takes place in a ‘bubble’, in which RNA is synthesized by base pairing with one strand of DNA in the transiently unwound region. As the bubble progresses, the DNA reforms behind it, displacing the RNA in the form of a single polynucleotide chain

4. Interrupted genes are expressed via a precursor RNA. Introns are removed when the exons are spliced together. The mRNA has only the sequences of the exons

5. Comparison of the restriction maps of cDNA and genomic DNA for mouse β-globin shows that the gene has two additional regions not present in the cDNA. The other regions can be aligned exactly between cDNA and gene

6. An intron is a sequence present in the gene but absent from the mRNA (here shown in terms of the cDNA sequence. The reading frame is indicated by the alternating open and shaded blocks; note that all three possible reading frames are blocked by termination codon in the intron

7. Most genes are uninterrupted in yeast, but most genes are interrupted in flies and mammals. (uninterrupted genes have only 1 exon, and totalled in the leftmost column)