Chapter 15.5: Eukaryotic pre-mRNA Splicing

Question 1

Define introns

Answer 1

portions of mRNA as transcribed from eukaryotic DNA that is removed by enzymes before the mature mRNA is translated into protein

Question 2

What are portions of mRNA as transcribed from eukaryotic DNA that is removed by enzymes before the mature mRNA is translated into protein?

Answer 2

introns

Question 3

Define exons

Answer 3

a segment of DNA that is both transcribed into RNA and translated into protein

Question 4

What is a segment of DNA that is both transcribed into RNA and translated into protein?

Answer 4

exons

Question 5

Define pre-mRNA splicing

Answer 5

in eukaryotes, the process by which introns are removed from the primary transcript to produce mature mRNA

Question 6

What is in eukaryotes, the process by which introns are removed from the primary transcript to produce mature mRNA?

Answer 6

pre-mRNA splicing

Question 7

Where does pre-mRNA splicing occur?

Answer 7

in the nucleus

Question 8

What is the first step of the pre-mRNA splicing process?

Answer 8

 The intron-exon junctions are recognized by small nuclear ribonucleoprotein particles, called snRNPs

Question 9

After  The intron-exon junctions are recognized by small nuclear ribonucleoprotein particles, called snRNPs, what is the last step of the pre-mRNA splicing process?

Answer 9

 These snRNPs cluster together with other proteins to form the spliceosome

Question 10

Define • Small Nuclear Ribonucleoprotein Particles (snRNPs)

Answer 10

in eukaryotes, a complex composed of snRNA and protein that clusters together with other snRNPs to form the spliceosome, which removes introns from the primary transcript

Question 11

What is in eukaryotes, a complex composed of snRNA and protein that clusters together with other snRNPs to form the spliceosome, which removes introns from the primary transcript?

Answer 11

• Small Nuclear Ribonucleoprotein Particles (snRNPs)

Question 12

Define spliceosome

Answer 12

in eukaryotes, a complex composed of multiple snRNPs and other associated proteins that is responsible for excision of introns and joining of exons to convert the primary transcript into the mature mRNA

Question 13

What is in eukaryotes, a complex composed of multiple snRNPs and other associated proteins that is responsible for excision of introns and joining of exons to convert the primary transcript into the mature mRNA?

Answer 13

spliceosome

Question 14

What is the first step of the splicing process?

Answer 14

 The splicing process begins with cleavage of the 5’ end of the intron

Question 15

After  The splicing process begins with cleavage of the 5’ end of the intron what is the next step of the splicing process?

Answer 15

 This 5’ end becomes attached to the 2’ OH of the branch point A, forming a branched structure called a lariat

Question 16

After  This 5’ end becomes attached to the 2’ OH of the branch point A, forming a branched structure called a lariat what is the next last of the splicing process?

Answer 16

 The 3’ end of the first exon in then used to displace the 3’ end of the intron, joining the two exons together and releasing the intron as a lariat

Question 17

When does the splicing process take place?

Answer 17

During transcription

Question 18

What is a consequence of the splicing process?

Answer 18

o One consequence of the splicing process is greater complexity in gene expression in eukaryotes

Question 19

Define alternative splicing

Answer 19

in eukaryotes, the production of different mRNAs from a single primary transcript by including different sets of exons

Question 20

What is in eukaryotes, the production of different mRNAs from a single primary transcript by including different sets of exons?

Answer 20

alternative splicing