Molecular Genetics Flashcards
Where is the growing polypeptide chain transferred to during the formation of a new peptide bond?
The growing polypeptide moves from the P site to the A site
What catalyzes the peptide bond between the polypeptide chain and incoming amino acid on the aminoacyl-tRNA
The ribosome
capsomeres
Series of protein subunits that make up a viral coat (capsid)
Capsomeres come together to form a protective protein coat called the capsid
Lytic cycle
Virus takes over host cell to replicate and causes harm to the host
What occurs during the lytic cycle?
Breaking apart the host genome and replicating many copies of viral nucleic acid
Many rounds of transcription and translation occur, allowing the viral genome to make many viral proteins
The copies of the viral nucleic acid can then be packaged into viral proteins to make new virus particles
The particles can then lyse (break apart) the host cell and go on to infect other cells
Silent mutation
Change in the DNA code that results in no change in what amino acid the codon codes for
This is due to degeneracy: several different condones code for the same amino acid
Proteins that play a role in DNA replication:
DNA helicase
Single strand binding protiens
Topoisomerase (DNA gyrase)
Primase
DNA polymerase
DNA sliding clamp
DNA ligase
Telomerase
Alternative splicing
Where different mRNA molecules are produced from the same pre-mRNA primary transcript
What does alternative splicing allow for?
Increased genetic diversity without increasing the size of the genetic code
DNA replication: initiation
The process of creating the origin of replication
DNA replication: initiation steps
- initiator proteins bind to specific sequences on DNA
- Recruitment of other proteins to the AT rich sequence
› helicase: breaks down hydrogen bonds between DNA strands and separates the strands
› single-stranded binding proteins: attach to DNA strands and keep the origin of replication open - Recruitment of other enzymes to synthesize daughter strands
RNAi molecules
- RNA interference
- interfere with mRNA via complementary base pairing to silence certain genes and prevent translation
- block gene expression using siRNA
What is the signal to end transcription in a eukaryotic cell?
The terminator sequence is the sequence in the DNA that signals the end of transcription and causes RNA polymerase to dissociate from the DNA
What mutations can result in frameshifts?
Insertions and deletions
Where does transcription occur in prokaryotes?
In the cytosol simultaneously with transcription because prokaryotes do not have membrane-enclosed nuclei
What is transcription?
The process of converting a sequence of DNA to mRNA before it can be translated into proteins
Steps of transcription:
1) Initiation: transcription factors on a promoter sequence (aka the promoter) attracts RNA polymerase to specific genes on the DNA strand
2) Elongation: begins after RNA polymerase has aligned and the transcription bubble has formed
3) Termination: RNA polymerase transcribed the terminator sequence (aka the terminator) which signals RNA polymerase to stop transcribing
In which direction does RNA polymerase travel during elongation step of transcription?
In which direction is the mRNA strand extended?
3’ —> 5’ direction on the template strand
Extends mRNA strand in the 5’ —> 3’ direction
Coding, non-coding and mRNA strand:
Coding (sense/anti-template strand): 5’ —> 3’ direction and is identical to the mRNA strand (T replaced with U)
Non-coding (antisense/template strand): 3’ —> 5’ complementary to both coding and mRNA strands. The strand in which RNA polymerase binds to and transcribes the mRNA strand
mRNA strand: 5’ —> 3’, identical to coding strand
What must occur before prokaryotic transcription can take place?
A sigma factor combined with prokaryotic core RNA polymerase to form the RNA polymerase holoenzyme, giving it the ability to target specific DNA promoter regions
Prophage
- viral genomes that integrate into bacterial genomes: bacteriophage infects a bacterial cell –> DNA is incorporated into the host genome –> considered a prophage
- host + viral genome = prophage
DNA polymerase extends the complementary strand in the ____________ direction
5’ —> 3’
DNA polymerase reads the template strand in the _________ direction
3’ —> 5’
Post transcriptional modifications:
The conversion of pre-mRNA into processed mRNA which leaves the nucleus —> 3 main types:
1) 5’ capping
2) polyadenylation of the 3’ end
3) splicing out introns
