Genes 1
What was the main conclusion of Beadle and Tatum's research? How has that conclusion been modified for current genetic thinking?
One gene/one enzyme, which has been modified to one gene/one polypeptide.
What are point mutations? How does a base substitution differ from a frameshift mutation? How do mutations relate to the process of evolution and natural selection?
2. In a base substitution, a letter is changed. In a frameshift mutation, a letter is added or deleted.
3. They drive evolution and natural selection.
Following elongation and termination, what structures are added to the ends of the RNA transcript? What sections of RNA are removed to change the initial RNA transcript into true mRNA?
1. 5' cap GTP, 3' poly-A tail
2. Introns are removed
What is a regulatory protein? How do they control gene expression (minor or major groove)? Why?
A protein that controls transcription by initiating or stopping it. It fits in the major groove because it can access hydrogen bond donors and acceptors.
How do gene control strategies differ between prokaryotes and eukaryotes? Why?
Prokaryote: Quick response, respond to environment; single-celled with no nucleus
Eukaryote: Maintain homeostasis; multicellular with a nucleus
What did Crick and Brenner determine regarding the concept of a reading frame?
Deleting one or two nucleotides shifts everything after the deletion (frameshift mutation).
Describe the basic structure of a ribosome. What are the three "sites" within the ribosome where the process of translation occurs? At which site does the first tRNA begin the process of translation initiation? What happens at the other two sites?
1. Large and small subunits
2. A (access site) P (peptide) E (exit site)
3. tRNA begins in the P site
4. 1st tRNA exits through E site, 2nd tRNA goes to A site to build polypeptide
How is prokaryotic transcription/translation different from eukaroytic transcription/translation? Why?
Prokaryotes do transcription and translation at the same time because they do not have a nucleus.
What is the difference between negative and positive control of transcription? What are the roles of repressors and activators in these different forms of transcription control?
1. Negative decreases the frequency of transcription, positive increases the frequency of transcription.
2. Repressors bind to operators that prevent/decrease initiation frequency.
Activators enhance binding of RNA polymerase to the promoter.
What is a DNA-binding motif? Which is most common?
The region of a regulatory protein that binds to DNA.
Helix-turn-helix
What is the basic structure of prokaryotic RNA polymerase?
Core polymerase and a holoenzyme (parrot shaped thing)
Describe the three main types of RNA found in transcription and translation.
1. mRNA: Intermediate form of DNA info
2. rRNA: Found in ribosomes, essential for protein production
3. tRNA: Involved in protein synthesis; reads mRNA and builds polypeptides
In what direction does transcription proceed? What three components are part of the transcription bubble in prokaryotes? How is prokaryotic transcription terminated?
1. 5' to 3'
2. RNA polymerase, DNA template, and RNA transcript
3. Series of G-C pairs followed by a series of A-T pairs
What is a transcription complex in eukaryotic cells? What are the four basic pieces of a transcription complex?
The transcription complex includes all the parts needed to transcribe DNA. In eukaryotes, this includes RNA polymerase 2, transcription factors, the promoter region, and the enhancer.
Describe the basic function of the lac operon; what are its components, and how does it work?
1. Encodes proteins needed to use lactose for energy
2. Lac repressor blocks enzymes that break down lactose (lactase) while glucose is present.
How many forms of RNA polymerase are found in eukaryotic transcription? What are their roles in the transcription process? Which one transcribes the mRNA?
1. Pol 1: Transcribes rRNA
2. Pol 2: Transcribes mRNA and snRNA
3. Pol 3: Transcribes tRNA and small RNAs
What is a codon? How many codons constitute the genetic code? How many are start/stop codons? How many codons are associated with amino acids? How many amino acids are there?
1. A block of 3 DNA nucleotides corresponding to an amino acid.
2. 64 total codons3. 1 start codon, 3 stop codons
4. 61 codons are associated with amino acids (none of the 3 stop codons have a corresponding amino acid)
5. 23 amino acids
Describe the eukaryotic initiation complex.
A transcription factor binds to the TATA box and recruits other transcription factors. RNA polymerase 2 later associated with the transcription factors and DNA. (TLDR; transcription factors + RNA poly 2)
What happens to DNA transcription function when it becomes methylated? Acetylated? What are chromatin-remodeling complexes and how do they influence transcription through action on nucleosomes?
1. Methylated: Inactivated
Acetylated: Activated
2. They move histones so that different sections of DNA can be read; they make DNA more accessible to regulatory proteins.
What is the role of general transcription factors in eukaryotic cells? How do they vary from specific transcription factors?
1. GTFs assemble the transcription apparatus and recruit RNA polymerase 2.
2. STFs react in a time/tissue dependent manner to increase transcription.
What is the difference between exons and introns in eukaryotic DNA/RNA? Which of these does prokaryotic DNA/RNA possess? In eukaryotic RNA, which are removed: exons or introns? Why? What is the term for this process of removal? What is the structure that actually does this activity?
1. Exons code for proteins, introns are non-coding
2. Exons
3. Introns; they don't code for anything
4. Splicing; spliceosome
What two sites on the DNA does initiation of prokaryotic transcription require? What is their position on the DNA in relationship to one another?
1. Promoter: Recognition and binding site for RNA polymerase
2. Start Site: Where RNA synthesis begins
The promoter region is upstream of the start site. (Promoter---->Start site)
Describe the stages of initiation, elongation, and termination in the process of translation.
1. Initiation: Initiator tRNA binds to the P site.
2. Elongation: 2nd charged tRNA binds to A site; the amino acid on the tRNA in the P site goes to the tRNA in the A site. The P site tRNA goes to E and exits, while the A site tRNA moves to the P site and the process repeats.
3. Termination: The process stops when a stop codon is reached.
What are the different forms of eukaryotic posttranscriptional regulation?
1. Small RNAs
2. RNA editing
3. Alternative splicing
4. mRNA degradation
How do chromatin-related actions (methylation/acetylation/etc.) relate to epigenetics?
They're the basis for epigenetics (how your behavior/environment changes the way your genes work); changes in chromatin affect transcription but not the DNA sequence.