KH 02 Flashcards
What is the central dogma of molecular biology?
DNA makes RNA makes protein
What does replication involve?
DNA synthesis
What does transcription involve?
RNA synthesis
What does translation involve?
Protein synthesis
What is the biopolymer, template and enzyme for replication?
DNA, DNA, DNA polymerase
What is the biopolymer, template and enzyme for transcription?
RNA, DNA, RNA polymerase
What is the biopolymer, template and enzyme for translation?
Protein, mRNA, ribosome
Most enzymes, including DNA and RNA polymerase, are _____.
proteins
What is the ribosome made of?
It has protein and RNA components. Both contribute to its enzymatic function
In transcription, what does the template?
The template, the exposed DNA strand, specifies RNA sequence by Watson-Crick base-pairing
What are rNTPs? ***
Ribonucleoside triphosphates
In transcription, is there a direct or indirect interaction of the template with the incoming monomer (rNTP)?
Direct
How do rNTPs diffuse?
Randomly. RNA polymerase will only link incoming rNTP to growing chain if it forms the perfect Watson-Crick base pair
RNA molecules are always synthesized in the ___ direction
5′ -› 3′
In transcription, is the nascent RNA chain parallel or antiparallel?
Antiparallel
In transcription, at which end does the chain grow?
The 3’ end
The polymerization catalyzes an attack of the ___ on the _____ of the incoming rNTP. Bêta and gamma _____ are dropped.
3’ -OH, alpha phosphate, diphosphate
The sequence of RNA transcribed from a region of DNA corresponds to the sequence of the _____.
non-template strand
The non-template strand and the new RNA strand are both _____ to, and _____ with, the template DNA strand
complementary, antiparallel
The template DNA strand is exposed by local unwinding of duplex DNA by _____.
helicase (associated with the RNA polymerase)
What moves along the DNA with RNA polymerase during transcription?
The transcription bubble
What happens after the DNA is unwound in the transcription bubble?
The original DNA duplex
re-forms behind the RNA
polymerase. The re-forming duplex behind
polymerase “kicks
out” the newly-synthesized
RNA strand.
How does the RNA polymerase move along the DNA?
Unidirectionally
During transcription, the displaced single-stranded
RNA exits through a channel
in the polymerase, __ end first.
5’
What are the names of the DNA sequences that facilitate the initial binding of RNA polymerase to the DNA during transcription?
Promoters
How does the RNA polymerase stop the DNA transcription?
Certain DNA sequences
destabilize the attachment of RNA polymerase to the DNA as it moves. The RNA polymerase falls off the DNA
and releases the completed RNA chain.
What are the similarities between DNA replication and transcription?
- Template = DNA
- DNA duplex locally unwound by a helicase at initiation sites to expose
template - New strand synthesized
5’ to 3’ antiparallel to
template. Chain growth at 3’ end - Monomers = nucleoside triphosphates
- Direct interaction (Watson‐Crick base pairing)
between template DNA and incoming monomer - Attack of 3’‐OH on alpha phosphate of
incoming dNTP. Bêta and gamma diphosphate
“dropped”
What are the differences between DNA replication and transcription?
- Transcription: Monomer = rNTPs / Replication: Monomer = dNTPs
- Transcription: Start and stop sites on template / Replication: Start sites (origins), but no stop sites
- Transcription: Newly synthesized strand (RNA) separates from template strand. / Replication: Newly synthesized strand (DNA) never separates
from template strand. - Transcription: Only one of the original DNA strands is a
template strand. / Replication: Both of the original DNA strands independently
serve as template strands. - Transcription: We start with one molecule of double‐
stranded DNA and we end with one molecule of double‐stranded DNA (plus the RNA molecule produced). / Replication: We start with one molecule of double‐stranded
DNA and we end with two molecules of double‐
stranded DNA
What do the 5’ and 3’ ends in an mRNA sequence respectively correspond to in the protein sequence?
NH2…..COOH
Nucleotides are “read” into amino acids as 3-character words called _____.
codons
How many 3-nucleotide codons are there?
64
What is the genetic code?
A dictionary of 3-nucleotide
codons and their corresponding amino acids. It is a 4 x 16 table.
What are the 3 STOP codons (terminaison codons), that do not code for any amino acid?
UAA, UAG, UGA (Stop)
What is the start codon?
AUG (Methionine or Met)
Can the STOP codon be present within the protein chain?
No
Can the START codon (Met) be present within the protein chain?
Yes
All proteins start their synthesis with ___.
Met
There is a _____ interaction of template with next
monomer molecule to be incorporated in replication and transcription.
direct
There is an _____ interaction between template and
next monomer to be incorporated (amino acid) in translation
indirect
tRNA acts as an _____ between template and growing chain
adaptator
What are the respective energized monomers for replication, transcription and translation?
dNTP, rNTP and aminoacyl tRNA
