Lecture 7 (recording 9)
*Molecular Definition of a Gene
-The entire nucleic acid sequence (usually DNA) that is necessary for the synthesis of a
protein (and its variants) or RNA.
-genes are segments of DNA that are transcribed into RNA.
-Two types of genes transcribed:
1. The resulting RNA encodes a protein
2. The resulting RNA functions as RNA
*RNA polymerase- transcription
*DNA polymerase and RNA difference
RNA polymerase does not need a primer to initiate(일으키다 시작하다) chain synthesis. It can
start by recognizing a complementary strand of DNA.
*Generation of RNA transcript:
1) Template: single stranded DNA
2) RNA (the rNTP) linked by Phosphodiester bonds
• DNA-RNA hybrid held together by Base pairing (Recording 10)
*The Transcription Cycle
-Sigma factor binds to promoter (specific sequences on DNA), the regions is where the RNA
polymerase is going to start the transcription.
-Transcription cycle starts. While sigma factor dissociate from RNA polymerase, RNA
polymerase goes through Abortive steps (RNA polymerase moves down the DNA strands
-Then Elongated phase, generate the complete transcript.
+Localized Unwinding of DNA by sigma factor, providing access to the template.
+hairpin loop: secondary structure of RNA getting formed telling RNA polymerase to stop.
+G-C reach region (result in the secondary structure, loop) & A-T reach regions (form weaker
base pairing in RNA, resulting the termination) ----“Rho Independent”.
The prokaryotic RNA polymerase holoenzyme......
A. consists of a sigma factor and the polymerase
B. requires ATP to unwind the DNA ( helicase….)
C. recognizes and binds to specific sequences at the transcription start site
(promoter sequence is an upstream to transcript, not a part of transcription)
D. Answers A, B, and C are correct
E. Answers A and C are correct
*Some key points about the transcription cycle
1) Initial steps of RNA synthesis are Relatively inefficient
2) This is quite different from elongation mode of RNA polymerase,
which is very…Highly Processive
3) What are some of the characteristics of RNA termin