Regulation of Gene Expression
What is it called when a nitrogenous base is changed, but the amino acid is the same as it was before?
silent mutation
What is the function of Primase in DNA replication?
Primase synthesizes RNA primers, using parental DNA as template
What is the difference between exons and introns?
exons are expressed and exit the nucleus, while introns intervene and never leave.
P site vs. A site vs. E site
P site: holds tRNA carrying the growing polypeptide
A site: holds tRNA carrying amino acid to be added to the chain
E site where discharged tRNAs leave ribosome
What do Viruses and bacteria have in common?
nucleic acids
what are control elements in eukaryotic genes?
segments of noncoding DNA that have special nucleotide sequences that serve as binding sites for transcription factors
What is the name of the enzyme that catalyzes the synthesis of DNA by adding nucleotides to the existing strand, and what direction are these nucleotides added?
DNA polymerase, 3' end
In what direction is mRNA built?
5' to 3'
What is the function of tRNA?
transfers amino acids from the cytoplasm to a growing polypeptide in a ribosome
What is the phenomenon of transformation?
A change in genotype and phenotype due to the assimilation of external DNA by a cell.
What is alternative RNA splicing?
when different mRNA molecules are produced from the same primary transcript
DNA replication occurs through a complex series of steps involving several enzymes. What is the correct order beginning with the earliest activity of enzymes involved in DNA replication?
Helicase, RNA primase, DNA polymerase, ligase
What is histone acetylation and how does it affect transcription?
histone acetylation is the addition of an acetyl group to an amino acid in a histone tail. This promotes transcription by helping to open up the chromatin structure.
Explain why prokaryotes can simultaneously perform transcription and translation, while Eukaryotes must complete transcription before starting translation.
Prokaryotes do not have a nucleus enclosing their DNA, so mRNA and bacterial DNA are not separated from the ribosomes. Eukaryotes have a nucleus and must transport mRNA to the cytoplasm for translation.
Lytic vs. Lysogenic life cycles (viruses)
Lytic: infects cell, takes over and produces new viruses until that cell bursts
Lysogenic: virus sticks DNA into bacteria's DNA and uses reverse transcriptase to copy DNA to host. The bacteria reproduces, virus DNA is included in each offspring. Lastly, viral DNA turns on and starts lytic cycle
What are the 2 main types of Negative Gene Regulation, and give a brief description.
Repressor: binds to operator and blocks attachment of RNA polymerase to promoter and prevents transcription.
Inducer: specific small molecule that inactivates the repressor
Leading strand vs. Lagging strand vs. Okazaki fragments
Leading strand: the DNA strand made by DNA polymerase III as it remains in the replication fork on a template strand and continuously adds nucleotides to a new complementary strand as the fork progresses. Requires only 1 primer for DNA pol III to synthesize entire strand.
Lagging strand: The DNA strand elongating in the direction away from the replication fork. Synthesized discontinuously.
Okazaki fragments: series of segments of the lagging strand. 100-200 nt long in eukaryotes.
Describe the post-transcriptional editing eukaryotes do to their RNA
A modified form of Guanine called the 5' cap is added to the 5' end, and a poly-A-tail is added to the 3' end.
What is a wobble?
When a nucleotide base can pair with more than one other base. For ex. U at 5' end of tRNA can pair with A or G at 3' end of mRNA codon.
Why are DNA strands labeled 3' and 5' on different ends, and how does that impact DNA replication?
The 3' end has a hydroxyl group, whereas the 5' end has a phosphate group. This impacts DNA replication because the new nucleotides can only join onto the 3' end due to the 5' end already having a phosphate.
What is the transcription initiation complex?
The complex of transcription factors and RNA polymerase II bound to the promoter.