Chapter 15 Flashcards
what is the central dogma of molecular biology?
DNA –> RNA —> protein
transcription, translation
what is transcription?
the flow of info from DNA to RNA
what is translation?
the flow of info from RNA to protein
how does DNA read amino acids?
in sets of 3 nucleotides for each amino acid
what is a codon?
3 nucleotides that specify a certain amino acid
what is a reading frame?
series of nucleotides that produce the right protein when read in sets of 3
what are proteins?
specific sequences of amino acids
who deciphered the genetic code and how many possible codons are there for the 20ish amino acids?
Nirenberg, 64 codons
can different codons represent the same amino acid?
yes
what are stop codons and which ones are they (3)?
UGA, UUA, UAG
terminate translation instead of coding for an amino acid
what is a start codon?
AUG, signifies the starting point of translation IF at the beginning of a sequence, if in the middle or end, it’s just Met
what is the remainder of the codons other than start and stop codons?
degenerate, where some amino acids are specified by more than one codon
what is the template DNA strand?
used to make RNA
what is the coding DNA strand?
complimentary to the template strand, not used to make RNA, but is same sequence as RNA but with T’s instead of U’s
what is RNA polymerase?
enzyme that synthesizes the primary RNA transcript using template DNA strand
list and describe the 3 steps of transcription
- initiation- RNA polymerase identifies a specific DNA sequence
- elongation- ribonucleotides are added to the 3’ end of the new RNA
- termination- RNa polymerase stops when it encounters a specific terminator DNA sequence
where does transcription take place in eukaryotes? in prokaryotes?
euk: nucleus
pro: cytoplasm
list and describe the 3 steps of translation?
- initation- mRNA, tRNA, and ribosome come together
- elongation- tRNAs bring amino acids to the ribosome to build the polypeptide
- termination- ribosome encounters a stop codon and releases polypeptide
where does translation occur?
cytoplasm for both bc that’s where the ribosomes are
list and describe the 3 types of RNA needed for gene expression
- mRNA- carries the info from DNA that encodes proteins
- rRNA- structural component of ribosome
- tRNA- carries amino acids to the ribosome for translation
at what rate does the transcription bubble move down the DNA template during prokaryotic transcription?
50 nucleotides/sec
what 3 things does the transcription bubble consist of?
all the things needed for transcription
- RNA polymerase
- DNA template
- growing RNA transcript
when does transcription stop in prokaryotes?
when the transcription bubble encounter terminator sequences, often includes a series of A-T base pairs
how is the primary transcript (initial RNA molecule) modified in eukaryotes? (2)
- additions of a 5’ cap and 3’ poly-A tail
2. removal of noncoding sequences (introns and exons)
what are introns?
stay in nucleus
what are exons?
will be translated
what do tRNA’s do?
carry amino acids to the ribosome to build polypeptides
what do aminoacyl-tRNA synthetases do?
add amino acids to the acceptor arm of tRNA
what does the anticodon loop of tRNA have?
3 nucleotide sequences complementary to mRNA codons
list and describe the 3 tRNA binding sites
- P site: binds the tRNA attached to the growing peptide chain
- A site: binds the tRNA carrying the next amino acid
- E site: binds the tRNA that carried to last amino acid to the chain
how does translation read the mRNA?
5’ to 3’
what are the 2 primary functions of the ribosome?
- decode the mRNA
2. form peptide bonds
what does peptidyl transferase do?
forms peptide bonds between amino acids
what stops translation?
the ribosome encounters a stop codon
what recognizes stop codons in translation and what do they do?
release factors; release the polypeptide from the ribosome
where can translation occur in eukaryotes?
RER or cytoplasmic ribosomes
