Bio 350: Molecular Genetics - Exam 3
What part of the ribosome does the ribosome binding sequence bind?
16S rRNA
Which below would you find in a prokaryotic ribosome?
16S rRNA
How many different types of aminoacyl-tRNA synthetases are there in a cell?
20
During active translation (i.e. when several codons of the mRNA have already been translated), how many tRNA's bind the ribosome at once?
3
What is the sequence of a start codon?
5' AUG 3'
How many different codons are there in the genetic code?
64
What two domains may an activator protein have?
A DNA binding domain and a transcription machinery recruiting domain
Which motif below might be found in a DNA binding protein?
A leucine zipper
How is an X-chromosome inactivated?
A long non coding RNA covers the X-chromosome
What tRNA binds to the stop codon?
A protein, not a tRNA, binds to the stop codon
What is a difference between an insulator protein and a repressor protein?
A repressor protein may bind an activator protein while an insulator protein does not.
In a prokaryotic cell, how does the ribosome bind the mRNA in exactly the right spot so that the start codon is in the P position?
A ribosome binding sequence interacts with ribosomal RNA to put the mRNA in the right spot
What molecule is added to the 3' end of a tRNA when it is charged?
An adenylylated amino acid
What is a common motif among DNA binding proteins?
An initiator tRNA ensures that the mRNA is aligned correctly
If 3 nucleotides are deleted in the middle of a exon the resulting protein will
Be missing one amino acid but the rest of the amino acids will be correct
What would you predict of a chromosome region where histone tails are methylated?
Because nucleosomes will cover transcription factor binding sites
Why does chromatin structure need to be modified to allow gene expression?
Because nucleosomes will cover transcription factor binding sites
In the CRISPR system, which group of proteins is involved in cutting the target sequence?
Cas proteins
What is heterochromatin?
Condensed regions of the chromosome where gene expression is repressed
In controlling gene expression in eukaryotes what nucleotide is methylated?
Cytosine
What is the first amino acid in a prokaryotic protein (prior to any post translational modifications)?
Formyl-methionine
You have isolated a new protein and you want to know if it is an activator protein by using a lac Z reporter plasmid. Evidence that your protein is indeed an activator protein would be:
If the colony is blue
What can be determined through a two hybrid assay?
If the two proteins of interest bind each other.
Where would you find the enzyme Argonaute?
In the RISC complex
What is an aminoacyl-tRNA?
It is a tRNA with an amino acid attached to it in a high energy bond.
What is a riboswitch?
It is an RNA sequence on the 5'end of mRNA that determines if the mRNA will be translated
What happens to the mRNA that has a complimentary sequence to miRNA?
It is degraded
How does the MerR protein activate transcription?
It twists the DNA in the promoter sequence thereby aligning the sigma factor binding sequences
An example of epigenetic gene regulation is
Methylation patterns in eukaryotic genes
Why would a prokaryotic cell have more than one type of sigma factor?
Multiple sigma factors allow a prokaryotic cell to control gene expression of various groups of genes at different times.
What does the ribosome do when a tRNA with the correct anticodon but charged with the incorrect amino acid enters?
Nothing, a ribosome cannot detect incorrectly charged tRNAs
How does eukaryotic mRNA circularize during translation?
Proteins attached to the 5'cap will bind to polyA tail proteins.
When glucose concentrations are high and lactose concentrations are very low....
The Cap activator will not be bound to DNA in front of the Lac operon but the Lac repressor will be
Where does the initiator tRNA bind in the ribosome?
The P postion
In eukaryotes, which protein is likely to bind first to initiate gene transcription?
The activator protein
An example of allosteric control of transcription by an activator protein is when
The activator protein changes an RNA polymerase from a closed to an open complex
In the gene in which this nucleotide is methylated what is likely to happen?
The gene will be silenced
What would you predict of a chromosome region where histone tails are acetylated?
The genes in this chromosome region are being expressed
If a virus produces a piece of double stranded RNA inside a cell, what would happen?
The mRNA that is complimentary to the ds RNA sequence would be degraded
What determines if a riboswitch manipulates the level of a specific protein inside cells?
The riboswitch will bind a metabolite closely associated to the substrates the protein works on.
If a bacterial small RNA activates gene expression what does it bind?
The sequence before the ribosome binding sequence that is complementary to the ribosome binding sequence.
38. During initiation of translation, how does the ribosome attach to mRNA?
The small subunit attaches first and after the preinitiation complex has been established the large subunit binds
How can the ribosome ensure that the correct tRNA has entered?
The tRNA has an anticodon that is a complementary sequence to the codon on the mRNA.
What part of the translational complex binds the growing polypeptide chain?
The tRNA in the P position
How does a tRNA synthetase recognize the correct tRNA?
The tRNA synthetase uses a combination of the anticodon and a discriminator base in the acceptor stem to recognize the correct tRNA.
What are CRISPR sequences?
They are a record of the organisms, such as viruses, that have infected the cell.
What do the enzymes Drosha and Dicer do?
They process pre-miRNA to generate mature miRNA
A gene adjacent to a Yeast telomere is likely...
To be silenced
What molecule causes the CAP activator to bind the activator sequence in front of the Lac operon?
cAMP
What part of the ribosome catalyzes the formation of the peptide bond?
rRNA
