i. Lecture "8ish" Slide Deck (January 30th)

Question 1

a) What is alternative splicing?
b) what is its purpose?

Answer 1

a) alternating what is being cut w/in an mRNA
b) allows for different mRNA to be produced from the same gene

Question 2

What regulates alternative splicing? Provide 2 examples

Answer 2

RNA-binding proteins such as sxl or Tra proteins (also Dsx)

Question 3

The following are all examples of RNA-binding proteins that regulates alternative splicing except
a) Dsx
b) sxl
c) Rbp1
d) Tra

Answer 3

c

Question 4

Describe the 5 steps involved in sex determination in drosophila resulting in a female using the following terms; sxl protein, tra protein, Dsx protein, exon 3, exon 2, exon 4, poly-A-tail, stop codon, splicing silencer, splicing activator, Rbp1, Tra 2, translation.

Answer 4

1. the splicing silencer sxl protein represses the splicing of the introns and instead encourages splicing of the introns and exon 3
2. more sxl protein is produced due to the stop codon in exon 3 being removed
3. sxl protein silencer the splicing of the intron and instead encourages splicing of the intron and exon 2
4. the splicing activator Tra protein is produced due to the stop codon in exon 2 being removed
5. the splicing activators Tra protein paired w/ Rbp1 and Tra 2 activate the splicing of the intro b/w exon 3 and exon 4
6. the female version of Dsx protein is produced due to exon 4 containing the poly-A-tail that terminates the translation of the mRNA

Question 5

Match the following
a) sxl protein
b) Tra protein
c) female Dsx protein
d) Dsx protein
1. removal of exon 2
2. removal of exon 3
3. removal of exon 4
4. keeping exon 4

Answer 5

a) 2
b) 1
c) 4
d) 3

Question 6

Describe the steps involved in sex determination in drosophila resulting in a male using the following terms; sxl protein, tra protein, Dsx protein, exon 3, exon 2, exon 4, poly-A-tail, stop codon, splicing silencer, splicing activator, Rbp1, Tra 2, translation.

Answer 6

1. due to there being no Sxl protein present only the introns are spliced resulting in the keeping of exon 3
2. exon 3 contains a stop codon that terminates the translation of the mRNA prematurely resulting in no sxl protein being produced
3. due to there being no sxl protein present only the intron is spliced resulting in the keeping of exon 2
4. exon 2 contains a stop codon that terminates the translation of the mRNA prematurely resulting in no Tra protein being produced
5. due to there being no Tra protein present exon 4 gets spliced out
6. Due to the removal of exon 4 the dsx mRNA continues to be translated resulting in the production of the Dsx protein

Question 7

Which of the following RNA-binding proteins officially determines the sex of the fruit fly?
a) sxl
b) dsx
c) Tra
d) all of the above

Answer 7

d

Question 8

a) What is Dsx?
b) what does the female isoform of Dsx contain?
c) what does the male isoform of Dsx contain?
d) What domain is the same in both sexes?

Answer 8

a) a transcription factor
b) an activation domain
c) a repressor domain
d) a DNA binding domain

Question 9

Match the following
a) sxl
b) Tra
1. splicing silencer
2. splicing activator

Answer 9

a) 1
b) 2

Question 10

What are the 2 roles of alternative splicing in neurons?

Answer 10

1. perceiving sound
2. neuron connectivity

Question 11

How does alternative splicing play an important role in perceiving sound?

Answer 11

depending on where the mRNA is spliced differ isoforms of the membrane Ca-activated K channels are activated resulting in the different frequencies being heard

Question 12

How deos alternative splicing play an important role in neuronal connectivity?

Answer 12

depending on where the DSCAM gene in fruit flies is spliced dictates which neuron it will connect to as only two neurons w/ matching homophilic binding regions can interact

Question 13

What is the major role that miRNA and siRNA play?

Answer 13

interfere w/ the translation of an mRNA of interest

Question 14

ANS the following wrt miRNA
a) do they match their target gene perfectly or imperfectly?
b) Where does it bind on the gene?
c) What does it do?
d) How does it do this?

Answer 14

a) imperfectly
b) 3’ UTR (3’ end of the untranslated region of the mRNA)
c) represses translation
d) prevents the docking of the ribosomes

Question 15

ANS the following wrt siRNA
a) do they match their target gene perfectly or imperfectly?
b) Where does it bind on the gene?
c) What does it do?
d) How does it do this?

Answer 15

a) perfectly
b) on the gene of interest (no specific location)
c) rapidly degrades the mRNA before it can be translated
d) by using the mechanism RNA interference

Question 16

at least a _______ of all distinct mRNA transcripts in mammals contain miRNA binding sites
a) half
b) third
c) fourth
d) fifth

Answer 16

b

Question 17

_______ regulates nearly every biological process to the point that w/out it you wouldn’t be able to develop beyond gastrulation
a) miRNA
b) tRNA
c) rRNA
d) siRNA

Answer 17

a

Question 18

Describe the following miRNA biogenesis proteins. Indicate whether they are found in the cytoplasm or the nucleus
a) Drosha
b) Exportin
c) Dicer
d) Argonaut
e) the RISC complex

Answer 18

a) removes the 5’ and 3’ ends of the pre-miRNA hairpin (nucleus)
b) it transports the pre-miRNA out of the nucleus (nucleus)
c) cuts the pre-miRNA hairpin forming double-stranded mature miRNA (cytoplasm)
d) the subunit of the RISC complex that acts a helicase by separating the double-stranded miRNA into two single-stranded miRNAs (cytoplasm)
e) holds and protects one of the single-stranded miRNAs from the nucleases (cytoplasm)

Question 19

What is miRNA/siRNA biogenesis?

Answer 19

the production of miRNA/siRNA

Question 20

How does argonaut related to the RISC complex?

Answer 20

Argonaut is the helicase subunit of the RISC complex

Question 21

Describe the 4 steps to the nuclear events in miRNA biogenesis including the following terms, drosha, dicer, argonaut, RISC, hairpin, pre-miRNA, miRNA, exportin, double-stranded, single-stranded, helicase
(Note: not all of these terms will be used)

Answer 21

1. transcribe miRNA
2. miRNA folds in on itself forming a hairpin
3. Drosha removes the 5’ and 3’ ends (cap and tail) of the hairpin forming pre-miRNA
4. exportin transports the pre-miRNA out of the nucleus

Question 22

Describe the 5 steps to the cytoplasmic events in miRNA biogenesis including the following terms, drosha, dicer, argonaut, RISC, hairpin, pre-miRNA, miRNA, exportin, double-stranded, single-stranded, helicase
(Note: not all of these terms will be used)

Answer 22

1. pre-miRNA enters and exits the cytoplasm using exportin
2. Dicer cuts the loop in the hairpin producing double-stranded miRNA
3. argonaut acts as a helicase by separating the strands producing 2 single-stranded miRNA
4. the guiding strand remains bound activating the RISC complex
5. the miRNA binds to its target gene where it represses the translation of that gene