DNA experiments & structure
A nucleotide is made of what three things?
sugar, phosphate group, and nitrogenous base.
This prevents dna from overwinding
Topoisomerase
What does the central dogma state?
genetic information flows in one direction: DNA->RNA->protein
Transcription takes place where?
In the nucleus
What elements are required for protein synthesis
1.mRNA template
2.ribosomes
3.tRNAs
4.enzymes
According to Chargaff's rule, the number of guanine = the number of ___, and the number of adenine = the number of ___?
cytosine, thymine
This strand is synthesized continuously
Leading strand
What is an amino acid composed of? What group changes?
Amino group, carbonyl group, side chain (changes)
What codes for protein sequences in mRNA processing
Exons
What do tRNAs carry
specific amino acid that recognizes one or more mRNA codons
What nucleotide bases are purines? Which are pyrimidines? How could you tell in a diagram?
Purine = adenine, guanine.
Pyrimidine = cytosine, thymine, uracil.
In a diagram, you can look at the structures. a double ring is a purine, a single ring is a pyrimidine.
A helicase produces what?
A replication fork
What are the three phases of prokaryotic transcription?
initiation, elongation, termination
What is the initiation complex made of?
Rna polymerase II bound and the pre initiation complex (transcription promoters bound to promoter)
what is the process of “charging”? What is associated with it?
Charging is a process that involves an aminoacyk tRNA synthetases adding the correct amino acid to the correct tRNA.
Watson and Crick proposed a model of DNA consisting of three things. What were these three things?
1) a double helical structure
2) phosphodiester bonds
3) purine - pyrimidine base pairings
False
How and why is a transcription bubble made?
Dna unwinds to allow RNA polymerase access to DNA-
True or false: tRNA and rRNA are translated
False
Termination occurs when what is encountered? What are the possible ones?
A nonsense codon : UAA UAG UGA
In the messelson stahl experiment, how DNA was shows to be semi conservative?
By placing 15N DNA into a 14N solution, each subsequent cell division would result in an increased uptake of 14N DNA, meaning that new DNA was being brought in with replication.
Which strand of DNA is synthesized in short stretches? What results because of this? How is this fixed later on?
The lagging strand. It results in Okazaki fragments, which are fixed by being brought together by DNA ligase to form one DNA molecule.
What is the difference in transcription termination when rho factors are present or not?
Rho dependent: Rho factor protein climbs up RNA transcript “bumps” into RNA polymerase Pulls transcript and DNA template strand apart
rho independent:
A GC-rich region of the transcript forms a hairpin The RNA polymerase stalls when it reaches the poly-A region of DNA Polymerase breaks away and transcript is released
What process do spliceosomes catalyze? What happens in this process?
They catalyze the slicing process, which involves removing introns from the primary rna transcript
In elongation, the amino acid in the P site is transferred to ?
The A site