Stamm 4-2 alternative splicing

Question 1

define alternative splicing

Answer 1

variant transcripts made form the same gene- usually cell type or development stage specific. Alternate transcripts within a cell are usually minor variants.

Question 2

if mutated, will cause alternative splicing

Answer 2

3’ AG splice site, 5’ GU splice site

Question 3

8 determinants of alternative splicing

Answer 3

COMBINATORIAL CONTROL: RNA folding can hide splice or poly-A sites; mutations in splice site; variation in the degenerate sequences before the 3’ splice site; repressor/activator protein expression; trans-acting RNAs; polymerase speed; chromatin structure

Question 4

example of how splice site is activated

Answer 4

in DSCAM, RNA interacts with itself (RNA:RNA interaction) to select ‘docking site’ at 3’ splice site before an exon- kicking off the ssRNA-binding repressor protein

Question 5

what bp is tolerated in RNA helices

Answer 5

UG, PLUS adenosine-derived inosine binds with anything

Question 6

function of enhancers

Answer 6

attract spliceosome

Question 7

function of silencers

Answer 7

repel spliceosome

Question 8

describe initial sex determination in drosophila (be prepared to determine mutation effects)

Answer 8

cells individually identify as a certain sex based on ratio of X chr to Autosomal (A) chr- 2X:2A females… 1X:2A males, which sets sexless splicing cascade into motion

Question 9

How are alternative exons detected in databases

Answer 9

because of multiple ways to determine alternative exon, must be experimentally determined

Question 10

Name two ways that alternative splicing can affect function

Answer 10

Can change the substrate binding activity of a receptor, Can change cellular localization signal on a protein

Question 11

Order of sexless cascade in female drosophila

Answer 11

higher X chr dosage leads to activation of sexless (sxl) gene promoter early in development, splicing out the stop codon, to create a splice silencer on the stop codon of tra (transformer), which acts with Tra2 to promote splicing of TF doublesex (dsx) which represses male genes