Bio 350: Molecular Genetics - Exam 3

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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


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