Key Terms
Genotype
The full collection of genes a cell contains. Stays constant.
Phenotype
Observable characteristics resulting from which proteins are being produced at a given time under specific conditions.
Leading strand
Synthesized continuously toward the replication fork. One primer.
Okazaki fragments
Short DNA fragments on the lagging strand, each initiated by a separate RNA primer. Discovered by Reiji and Tsuneko Okaz
Human genome
3 billion base pairs per haploid set; 6 billion inserted during replication.
Linear chromosomes face a problem
DNA pol cannot replicate the very end of the lagging strand template. Without a fix, chromosomes would shorten with ever
Used by
Some plasmids, some bacteriophages, some eukaryotic viruses.
Mechanism
1. One strand of circular dsDNA is nicked at the double- stranded origin (dso).
Transcription
DNA sequence copied into a single-stranded RNA molecule. The template strand is the antisense strand.
Transcription bubble
Region of locally unwound DNA where synthesis occurs.
Promoter
DNA sequence upstream of the gene where RNA pol binds. Key consensus sequences in bacteria:
Prokaryotic mRNA
Often polycistronic (encodes multiple polypeptides).
Eukaryotic mRNA
Exclusively monocistronic (one mRNA = one polypeptide).
Eukaryotic mRNA lifespan
Several hours. Prokaryotic mRNA lifespan: typically no more than 5 seconds.
Codon
A triplet of mRNA nucleotides that specifies one amino acid (or stop). 64 possible codons (4^3).