Biochemistry 2280A Lecture Notes - Lecture 24: Primary Transcript, Intron, Polyadenylation

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17 Dec 2015

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Topic 24: rna processing in eukaryotes lecture notes. When a transcript is first made, it ends with a triphosphate. First nucleotide that comes in is a triphosphate. Happens as soon as the rna is exposed in eukaryotes, a 7-methylguanosine is added to that linkage is a 5"-5" linkage (unique) Marks the 5" end of the mrna as being intact. Required for: mrna export from the nucleus, translation of the mrna. Primary transcript would still have rna polymerase working. After the stop codon, there is a sequence that resembles aauaaa. Recruits an enzyme that clips the rna 30 bases downstream and then. String of a bases can be as long as 300, very long tail at the end of the. Happens with transcription ongoing in eukaryotic cells adds a long string of a bases mrna. Marks the 3" end of the mrna as being intact. Protein encoding sequences (exons) are interrupted by noncoding sequences (introns)

Related Questions

QUESTION 1

Which of the following statements regarding splicing is FALSE?

A) The length of introns determines the efficiency of splicing.

B) Many human neurological disorders are caused by splicing errors and/or mutations in splicing factors.

C) Splicing requires the action of a variety of snRNAs that direct the transesterification reactions.

D) Splicing is dictated by sequence features in pre-mRNA transcripts

QUESTION 2

Which of the following mRNA processing factors does NOT associate with the CTD of RNA polymerase II?

A) splicing factors

B) polyadenylation factors

C) miRNAs/siRNAs

D) capping proteins

QUESTION 3

Which of the following statements about mRNA stability is FALSE?

A) Deadenylation-independent mRNA decay is exclusively in the 5' to 3' direction.

B) The most common pathway of mRNA decay is deadenylation-dependent.

C) Yeast mRNA decay occurs primarily in the 5' to 3' direction, while 3' to 5' decay is more common in mammalian cells.

D) Decapping enzymes are required for all pathways of mRNA decay.

QUESTION 4

You obtain the sequence of a gene containing 10 exons, 9 introns, and a 3â² UTR containing a polyadenylation consensus sequence. The fifth exon also contains a polyadenylation site. To test whether both polyadenylation sites are used, you isolate mRNA and find a longer transcript from muscle tissue and a shorter transcript from all other tissues. Which of the following is the most likely mechanism underlying these alternative transcripts?

A) The fifth exon is spliced out of the mature mRNA transcript in muscle cells.

B) Muscle cells have less effective polyadenylation than other tissues.

C) An alternative CPSF protein is expressed in muscle cells with lower affinity for the polyadenylation sequence in exon 5.

D) The mRNA in muscle cells is edited to eliminate the polyadenylation sequence in exon 5.

blushdonkey474

Fill in the blank. Elongation during translation does NOT involve ____________.

Question 16 options:

	the translation of codons according to the genetic code
	the formation of bonds catalyzed by the ribosome
	complementary base pairing between RNA molecules
	amino acids being linked together in a polypeptide
	reading the DNA template 3' to 5'

For a given gene, what establishes the reading frame for translation?

Question 17 options:

	the location of the enhancer relative to the gene
	the first three nucleotides at the 5' end of the mRNA
	the first three nucleotides at the 3' end of the mRNA
	the start codon in the mRNA
	the location of the promoter relative to the gene

Which of the following is the LEAST likely direct consequence of a substitution mutation?

Question 18 options:

	changing the length of a protein coded for by a gene
	changing one amino acid in a protein
	creating a stop codon
	eliminating a start codon
	changing the length of the DNA molecule containing a gene

Suppose that the pre-mRNA transcript from a eukaryotic gene is 30,000 nucleotides long, and the gene codes for a sequence of 300 amino acids. What is the best explanation for the relationship between these numbers?

Question 19 options:

	only the first 900 nucleotides of the pre-mRNA transcript are translated
	it takes 100 nucleotides to specify a single amino acid
	300 of the nucleotides in the transcript are important, and the rest are "junk"
	only the last 900 nucleotides of the pre-mRNA transcript are translated
	large portions of pre-mRNA transcripts are cut out during RNA processing

Suppose an individual is born into a population with a novel mutation. Is the new mutation an evolutionary change, and why?

Question 20 options:

	no, because it is not a big enough change to count
	yes, because new mutations are always adaptive
	yes, because the appearance of a new genetic variant is a genetic change in a population
	no, because not enough individuals have the mutation for it to matter
	no, because most mutations are not adaptive

If one is testing a goodness of fit to a 9:3:3:1 ratio, how many degrees of freedom would be associated with the Chi-square?

not enough information to determine

Which of the following choices does not describe a type of posttranslational modification of proteins?

The amino terminal methionine may be removed.

Glycoproteins are produced by the attachment of phosphates to newly synthesized proteins.

Precursor proteins are cleaved and trimmed by protease enzymes to produce a functional protein.

Molecular chaperones help proteins fold correctly.

Amino acids in the amino terminal of the protein can be acetylated.

A eukaryotic DNA sequence that affects transcription at distant promoters is called a(n)

long distance promotor

regulator

operon

enhancer

DNA methylation may be a significant mode of genetic regulation in eukaryotes. Meythylation refers to

altering RNA polymerase activity by adding methyl-groups

changes in DNA-DNA hydrogen bonding

altering translation activity via methylated tRNAs

adding methyl groups to certain cytosines in DNA

If a nucleotide lacks a 3â-OH group, what will happen?

itâs transformed into RNA

another nucleotide can bond at the 3â site during replication

replication will halt

no effect

Which of the following describe posttranscriptional modifications commonly seen in mRNA of eukaryotes?

5â capping, 3â-poly-A tail addition, splicing

3â capping, 5â poly-A tail addition, splicing

heteroduplex formation

5â capping, 3âpolyA tail addition, removal of exons

In birds, females are the heterogametic sex. This means that

females have chromosomes in pairs.

emales produce eggs.

females determine the gender of their offspring.

males have two identical sex chromosomes (ZZ)

An anticodon on a tRNA has the sequence 5'âGCAâ3'. What would be the effect on translation if the G in the anticodon were mutated to a U?

The anticodon could pair to the serine codon 5'âUCAâ3', and a cysteine would be incorporated at all points where a serine should have been incorporated.

The anticodon could pair to the threonine codon 5'âACUâ3', and a threonine would be incorporated at all points where a cysteine should have been incorporated.

The anticodon could pair to the serine codon 5'âAGUâ3', and a serine would be incorporated at all points where a cysteine should have been incorporated.

The anticodon could pair to the stop codon 5'âUGAâ3', and instead of stopping translation, a cysteine would be incorporated and translation could continue.

Biochemistry 2280A Lecture Notes - Lecture 24: Primary Transcript, Intron, Polyadenylation

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