Molecular Biology - Rna Splicing

Front 1

Most eukaryotic genes are composed of ___ and ___. Which are coding parts?

Back 1

exons and intron, exons

Front 2

RNA splicing involves the removal of __ and splicing of ____ into a continuous reading frame for translation.

Back 2

introns, exons

Front 3

Prokaryotes doe not generally have extensive ___ . Exceptions include __ __ __ and __ ___.

Back 3

introns

group II introns

plasmid introns

Front 4

More complex organisms have more ___ .

Back 4

introns

Front 5

Yeast genes usually have ___ intron(s).

Back 5

one

Front 6

The longest primary transcript is produced by the __ gene

Back 6

dystrophin

Front 7

exons are generally ___ than introns

Back 7

shorter

Front 8

Why must introns be removed before translation in eukaryotes?

Back 8

The translational machinery can not distinguish between introns and exons.

Front 9

What is alternative splicing?

Back 9

When more than one type of mRNA can be produced by one gene (some have over 100)

Front 10

Introns have a generic ___ ___ to deliniate the intro exon junctions. This includes a ___ spice site and a __ splice site.There is a third conserved element in the middle called the __ __ __.

Back 10

5', 3', branch point site

Front 11

The branch point site is followed downstream by a ___ ___

Back 11

polypyrimidine tract

Front 12

Splicing occurs through two successive ____ reactions, in which existing ____ bond are transferred from one location to another. Explain.

Back 12

transesterification, phosphodiester

The 2'OH of the conserved A at the branch site is nucleophillically attacked by a phosphoryl goup on the 5' splice site. To create the three way junction. The 3'OH on the free end attacks the phosphoryl group on the 3' splice site. And the intron is the leaving group.

Front 13

In splicing of an intron no energy input is required, why?

Back 13

Because two phosphodiester bonds are broken and two are made.

Front 14

In alternative splicing, some exons can be ___.

Back 14

skipped

Front 15

What is trans-splicing?

Back 15

Exons from different RNA molecules are spliced together

Front 16

What is the large protein complex that carry out RNA splicing transesterification reactions?

Back 16

splicesome

Front 17

How can RNA carry out some of the events in RNA splicing?

Back 17

Because they can be catalytic, they can catalyze their own reactions like enzymes.

Front 18

What are the 5 RNAs in the splicesome (small nuclear RNAs snRNAs)? What are the proteins that they are associated with called?

Back 18

U1, U2, U4, U5, U6

snRNPs

Front 19

The snRNPs are responsible for?

Back 19

1. recognition of the 5' splice site and branch site

2. bringing these regions together

3. helping catalyze the RNA cleavage and joining reaction

Front 20

What is the sequence of events of the splicesome to form the early complex or E complex?

Back 20

1. U1 recognizes 5' site

2. U2AF binds to the PY tract AND 3' splice site

3. U2AF recruits BBP to the branch site

Front 21

Steps to A complex?

Back 21

1. U2AF aids in binding U2 to the branch site

2. BBP is displaced

Front 22

Steps to B complex?

Back 22

1. tri-snRNP are recruited (U4, 5, 6)

2. the three splice sites come together

Front 23

Steps to C complex?

Back 23

1. U6 replaces U1

2. U4 is relased, U6 and U2 interact

3. Now there is a functional active site

Front 24

Steps to remove the lariat?

Back 24

1. U5 aids in attack between 5'/3' sites

2. lariat is relased and degraded

3. snRNPs are recylced

Front 25

What kind of introns do not require the splicesome?

Back 25

self-splicing introns (group I and group II)

Front 26

How do organism avoid inappropriate splicing?

Back 26

1. splicesome is only assembled on specific sequences

2.

Front 27

What are ways that errors can occur in splicing?

Back 27

1. Exons can be skipped

2. pseudo splice sites are spliced in

Front 28

In what ways are splice specific selection enhanced?

Back 28

1. After encountering 5' splice site, proteins on the tail transfer to the RNA and the next 3' splice site is recognized before any downstream site can be transcribed

2. serine-rich SR proteins that bind to ESEs in the exons, promoting more efficient binding of splicesome machinery, SR proteins recruit U2AF

Front 29

constitutive alternative splicing

Back 29

more than one product is always produced

Front 30

regulated alternative splicing

Back 30

done in response to a specific cellular signal, allows different forms of the transcribed RNA to be produced at diff times

Front 31

SV40 virus produces what two proteins?

Back 31

T-ag, t-ag, depending on level of splicing protein

Front 32

What is an extended exon?

Back 32

includes a portion of an intron with a stop codon

Front 33

Othe ways that alternative splicing occurs

Back 33

1. steric hindrance

2. major and minor splice sites

3. repressor proteins can cause a skip

4. activators can cause a splice

Front 34

Why are introns absent in bacteria?

Back 34

1. introns late model, introns were never present, but arose during evolution

2. or introns were originally present and were evolved out to minimize genomes to accomodate selective pressure

Front 35

Why do eukaryotes have introns?

Back 35

1. for alternative splicing

2. new genes can be created by shuffling

(each exon codes for a specific domain of a protein, they can be mixed and matched)

Front 36

What is RNA editing? And what are the two ways it occurs?

Back 36

When the RNA is changed after transcription

1. site-specific deamination

2. RNA directed uridine insertion or deletion

Front 37

The mRNA is exported where?

Back 37

Through the nuclear pore complex

Front 38

True or false. The bigger the genome the more complex the organism.

Back 38

false

Front 39

So what explains the differences in biological complexity?

Back 39

1. alternative splicing

2. PTMs

3. protein-protein interactions and their integration into pathways, proteins with a variety of isoforms that carry out more than one function