Lecture 10

Question 1

How is alternative splicing of RNA negatively regulated?

Answer 1

Repressor prevents splicing machinery access to splice site

Question 2

How is alternative splicing of RNA positively regulated?

Answer 2

Activator recruits and helps direct splicing machinery

Question 3

What structure of the mRNA confers its stability?

Answer 3

poly-A tail

Question 4

How does shortening of the poly-A tail or de-capping of the 5’ end affect RNA?

Answer 4

Shortening of poly-A ail acts as a timer; this acts with de-capping to signal degradation of mRNA

Question 5

How are Transferrin Receptor and Ferritin regulated during times of iron starvation?

Answer 5

More transferrin receptor mRNA should be made, less ferritin mRNA produced; IRP binds to IRE at 5’ end of ferritin mRNA

Question 6

How are Transferrin Receptor and Ferritin regulated during times when iron is in excess?

Answer 6

Less Transferrin Receptor mRNA will be made, more Ferritin mRNA will be produced

Question 7

How do microRNAs regulate mRNA?

Answer 7

Precursor miRNA cropped in nucleus and forms double stranded loop structure; Further cleaved by Dicer enzyme; joins with other proteins to form RISC; base pairs with mRNA, then cleaves and shuts down RNA expression

Question 8

Give examples of post-translational modifications to proteins

Answer 8

Folding by molecular chaperones, binding of co-factors, protein kinase modification, glycosylation, enzymatic activity, binding to other proteins

Question 9

What is the purpose of heat shock proteins (Hsps)?

Answer 9

Helps proteins refold appropriately after exposure to high temperatures

Question 10

What is the mechanism of protein regulation via proteasomes?

Answer 10

Proteasomes remove and destroy misfolded proteins. Structure contains ATP dependent active sites and cap that acts as a gate for proteasome.

Question 11

Explain how Ubiquitin regulates proteins via degradation

Answer 11

E1 and ubiquitin are linked; ubiquitin transferred to E2 ligase with E3 accessory protein; protein with degradation signal is added to ubiquitin ligase and ubiquintin continually added to target protein to be recognized by proteasome.

Question 12

Coordinated Gene Expression

Answer 12

One critical protein can affect many downstream genes. Can be expressed in response to need such as with glucocorticoid cortisol

Question 13

Decision for Specialization

Answer 13

Gene combinations mediated by regulatory proteins can produce many different types of cells (Ex: hematopoiesis)

Question 14

DNA Methylation

Answer 14

Represses/silences gene expression; such as in genomic imprinting

Question 15

X-inactivation

Answer 15

Dosage compensation so that an equal number of genes are expressed from X chromosomes in males and females - results in presence of Barr Body in females

Question 16

True or False: MicroRNAs bind to mRNAs to activate the mRNAs to be active to produce large amounts of proteins.

Answer 16

False