Gene Expression Flashcards
What is central dogma?
Term coined by Francis Crick to explain how information flows in cells.
What are nucleosomes?
DNA wound around histones
What does topoisomerase 1 do?
Bends DNA to bind with histones
What are the two types of interphase chromatin?
Heterochromatin and euchromatin
What is heterochromatin?
highly condensed
visible with a light microscope
is not transcribed
What is euchromatin?
“true chromatin”
less compact
transcribed
What does the addition of acetylcholine groups to histones cause?
causes them to becomes less tightly packed, allowing for access to the DNA
What is DNA Methylation?
the attachment by specific enzymes of methyl groups (-CH3) to DNA bases after DNA synthesis.
What is an example of DNA methylation?
the inactivated mammalian X chromosome in females is heavily methylated
Which genes are more heavily methylated?
In cells where they are not expressed
What does tRNA do?
Carries amino acids to the ribosome during translation to help build an amino acid chain
What performs transcription?
RNA polymerase
What are the three stages of transcription?
initiation, elongation, and termination
What does RNA polymerase do?
links nucleotides to form an RNA strand using DNA as the template
RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription.
What is the promoter called in eukaryotes?
TATAA box
Where does RNA polymerase bind to during transcription?
To a sequence of DNA called the promoter
What are activators in transcription?
Activators are proteins that binds to an enhancer region on the DNA and stimulates transcription
What are bound activators?
Facilitate a sequence of protein-protein interactions
Results in transcription of given gene
What strand of DNA acts as a template for RNA polymerase?
Antisense
What is the non-template strand of DNA called?
Coding or sense strand
What is an example of a termination mechanism?
The formation of a hairpin in the RNA
What are snRNPs?
RNA-protein complexes that combine with unmodified pre-mRNA and other proteins to form a spliceosome
What is splicing?
parts of the pre-mRNA (called introns) are chopped out, and the remaining pieces (called exons) are stuck back together
What is translation?
A ribosome reads the information in an mRNA molecule and uses it to build a polypeptide
How many codons are there for amino acids?
61
What codon/amino acid acts as a start codon?
Codon: AUG
Amino acid: methionine
What are the stop codons?
UAA, UAG, UGA
What is the only non-membrane bound organelle?
Ribosomes
What are the three sites of ribosomes and what do they do?
A site- “aminoacyl”- where amino acids enter the ribosome
P site- “peptidyl”- where the growing polypeptide is kept
E site- “exit”- where empty tRNA molecules leave
What enzyme is used to add amino acids to tRNA molecules?
aminoacyl tRNA synthetase
What does peptidyl transferase do?
Link the existing amino acid chain onto the amino acid of the tRNA
What is RNA interference mediated by?
tiny RNA molecules called miRNA (Micro RNA)
How are miRNAs produced?
the transcript for them is cleaved into multiple fragments by a “dicer” protein
What is the protein that maintains post-translational gene control?
Ubiquitin
What type of mutation causes sickle cell anemia?
Point mutation
