Chapter 12
What are the 3 stages of Transcription ?
1. initiation: RNA polymerase binds to the promoter 2. Elongation: RNA polymerase uses the template DNA strand to join RNA nucleotides together to make a complementary RNA strand 3. termination: transcription terminates after RNA polymerase reaches a terminator sequence (prokaryotes) or a polyA signal sequence (eukaryotes), and RNA polymerase dissociates from the DNA
what is a codon(what does a codon specify)? How many nucleotides are in a codon?
A codon is a sequence of 3 nucleotides that specifies an amino acid
What are the base pairing rules between DNA and RNA?
A pairs with U C pairs with G U pairs with A G pairs with C
What is a gene ?
A segment of DNA that encodes a functional product
What two macromolecules is a ribosome composed of ?
A type of functional RNA called ribosomal RNA (rRNA) and proteins .
What do genes encode ?
About 90% of genes encode a polypeptide but about 10% encode functional RNA molecules, such as ribosomal and transfer RNA
Put the following flow of genetic material in the correct order.
DNA-RNA-polypeptide
Which amino acid does the codon 5'-GGA-3' encode?
Gly
What are introns and exons?
Introns are non-coding regions of eukaryotic genes that do not get translated to amino acid. Introns get spliced out during pre-mRNA processing. Exons are the coding regions of a eukaryotic gene that get translated to amino acid
A strand of nucleic acid has the sequence: 5'-ATT GCC-3'. It is a DNA or an RNA strand?
It is a DNA strand because it contains the base thymine.
A strand of nucleic acid has the sequence: 5' - AUC GAU - 3'. It is a DNA or an RNA strand?
It is an RNA strand because it contains uracil
Is a new RNA strand transcribed in the 5'-3' or the 3'-5' direction? Why?
It is transcribed in the 5'-3' direction. RNA polymerase can only add incoming nucleotides to the 3' end.
What does it mean to say that the genetic code is degenerate ?
It means that the same amino acid can be specified by more than one codon
Which amino acid does the codon 5'-CUG-3' encode?
Leu
What is messenger RNA (mRNA)?
Messenger RNA (mRNA) is an RNA copy of a gene that contains the info. to make a polypeptide
What is the sequence of amino acids encoded by the mRNA:5'- AUG ACG GAC CCA GGU UAA-3'
Met - Thr - Gln - Pro - Gly
What is the function of RNA polymerase?
RNA polymerase uses the DNA template strand to link RNA nucleotides together to form a complementary strand of RNA
What is splicing, and what complex performs splicing?
Splicing is the process that removes inrons and joins together the exons. The spliceosome performs splicing. It is a complex composed of many proteins and functional RNA molecules called small nuclear RNAs(snRNAs).
A tRNA has the anticodon 3'-UGC-5' Which amino acid does it carry?
The corresponding codon is 5'- ACG-3', which encodes Thr
A tRNA has the anticodon 3'-UAU-5'. What amino acid does it carry?
The corresponding codon is 5'- AUA-3', which encodes Ile
If the DNA coding(non-template) strand is 5'- AGG TAG CCA GGT-3' what is the corresponding mRNA sequence?
The corresponding mRNA has the same sequence as the coding (non template) DNA strand except U instead of T, so: 5'-ACG UAG CCA GGU-3'
If the DNA coding (template) strand is 5'- AGG TAG CCA GGT-3' what is the corresponding mRNA sequence?
The corresponding mRNA is complementary to the DNA template (non-coding) strand, so: 3'- UGC AUC GGU CCA-5'
How does alternative splicing allow one gene to encode more than one protein?
The gene can be alternatively spliced by joining together different combinations of exons.
What is a regulatory sequence ?
The place where regulatory proteins bind to the DNA to control the rate of transcription
What is a transcribed region?
The region of DNA that gets copied to RNA
What is transcription?
The sequence of DNA nucleotides in a gene is copied to a sequence of RNA nucleotides
What is translation ?
The sequence of nucleotides in mRNA is converted to a sequence of amino acids in a polypeptide. It specifies the order that amino acids will be linked together to form a polypeptide
A codon is 5'-ACG-3'. What is the sequence of the tRNA anticodon that will bind, and which amino acid does the tRNA carry?
The sequence of the tRNA anticodon is 3'-UGC-5' and the tRNA will carry the amino acid Thr, which is the amino acid encoded by the codon.
Where does translation take(polypeptide synthesis) take place?
Translation takes place at the ribosome. Ribosomes are the cell's protein factories.
What is a Ribosome binding site?
in prokaryotes it is the site in the mRNA where the ribosome binds. In eukaryotes, the 5' cap serves as the ribosome binding site
What is a stop codon?
specifies the end of translation(the stop codon does not encode an amino acid)
What is a start codon?
specifies the first amino acid, which is methionine
What is the function of tRNA? What is an anticodon?
tRNAs are functional RNA molecules that bring amino acids to the ribosome. A tRNA molecule has an anticodon at one end and it carries an amino acid at the other end. The anticodon recognizes a specific mRNA codon and carries the amino acid that is specified by the mRNA codon. An anticodon is a sequence of 3 nucleotides in the tRNA molecule that recognizes the codon. The anticodon is complementary in sequence to the codon.
What is a gene promoter?
the place where RNA polymerase binds to the DNA to begin transcription
What is a terminator or polyA signal sequence?
the region where transcription ends
What is a coding sequence?
the sequence of nucleotides in mRNA that encode amino acids. The start codon is the start of the coding sequence and the stop codon is the end of the coding sequence
Which amino acid does the codon 5'-UGA-3' encode?
trick question. It does not encode an amino acid as it is a stop codon. A release factor will bind to the stop codon to end translation
