pairs do not get paired, which shortens the genome over time. These ends are called telomeres and ae not coded. The base-pair sequence of TTAGGG is repetitively copied up to 1000 times to make the telomere. Telomerase is an enzyme that attaches to the end of the chromosome to add telomeres in cells like germ cells and adult stem cells, which remain “youthful” for extended periods of time. It isn’t active in adult somatic cells and may be responsible for the aging of cells because the telomeres shorten. Plasmids also undergo DNA replication. While some replicate like bacterial DNA, others use the rolling circle replication technique. One piece of the double strand of DNA is nicked and then the DNA polymerase will help to make a copy of the un-nicked strand. The nicked strand may then circularize again and can get replicated. This leads to two copies of the plasmid.
RNA TRANSCRIPTION Transcription happens when DNA is used as a copy to make an RNA transcript, which is single-stranded. It requires partial unwinding of the DNA segment and the formation of a transcription bubble. The antisense strand is the one that gets transcribed. This makes the RNA segment made a near-exact copy of the sense strand. Transcription involves RNA polymerase, which works from the five-prime to threeprime end. RNA polymerase does not involve a primer but DNA polymerase does. Complementary RNA base pairs are added to match the DNA segment being transcribed. There are six subunits to the bacterial RNA polymerase. The sigma subunit is responsible for binding of the enzyme to a promotor site at the beginning of transcription. Transcription always starts at a promoter site. The first DNA piece to be transcribed is called the initiation site. Nucleotides are added downstream from the initiation site. There are similarities in the promotor regions of all bacteria, which are the sites of RNA polymerase attachment. This usually involves what’s called a TATA box, which is a TATAAT sequence of DNA bases. Elongation happens at about 40 nucleotides per segment, getting made from the five-prime to three-prime end.
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