Exam #4: Transcription, RNA Processing & Control of Gene Expression Flashcards Preview

Biochemistry > Exam #4: Transcription, RNA Processing & Control of Gene Expression > Flashcards

Flashcards in Exam #4: Transcription, RNA Processing & Control of Gene Expression Deck (48)
Loading flashcards...
1

3 Ways RNA Differs from DNA

1) Ribose sugar instead of Deoxyribose
2) No thyamine, Uracil instead
3) Single stranded instead of double stranded

2

What is the significance of the DNA template in transcription?

DNA is the template for the synthesis of the complimentary RNA molecule

3

2 Differences Between DNA & RNA Polymerase

1) RNA Polymerase initiates RNA synthesis without a primer
2) RNA Polymerase is much more error prone

4

RNA Class Translated into Protein

mRNA

5

DNA Sequence that Specifies Start

- Promoter
- TATA box, CAAT box, & GC rich regions

6

DNA Sequence that Specifies End

- Terminator
- Polyadenylation

7

Typical "Layout of a Gene"

- Enhancer elements far upstream of start site
- Gene-specific (regulatory elements)
- CAAT or GC rich region
- TATA box
- Transcription start point

8

Alpha-Amanitin

-Toxin found in the "Death Cap" Mushroom
- inhibits Pol II & blocks synthesis of mRNA
-Results in liver failure

9

How does Rifampicin kill bacteria and not harm human cells?

- Potent antibiotic
- Inhibits bacterial RNA polymerase but not human Pol II

10

Capping

- 5' methylguanosine cap is put on pre-mRNA
- Distinguishes mRNA from other forms of RNA

11

Exon

Gene region that codes for protein

12

Intron

Gene region that is non-coding & spliced out

13

pre-mRNA splicing

- Removing introns from pre-mRNA
- Spliceosomes: recognize boundaries, cleave, & rejoin

14

Outline the Process of Splicing

- Adenine residue attacks the 5' splice site & cuts backbone
- 5' end becomes covalently attached to adenine, forming a loop
- Newly generated free 3' end reacts with the next 5' end to join the exons together
-Lariat intron structure is released

15

How are the boundaries of introns and exons defined?

- 5' splice site
- 3' splice site
- branch point in middle
- AGG consensus sequence

16

Alternative Splicing

- Splicing different combinations of exons together to generate different proteins

17

Polyadenylation

- Tail of roughly 200 adenine nucleotides added to mRNA
- unique to mRNA

18

B-Thalassemia & Splice Errors

- Incorrect splicing leads to reduced synthesis of the B-chain of Hb
- Less B chain= less Hb & profound anemia

19

PKU & Splice Errors

- Lack of phenylalanine hydroxylase activity results in an inability to convert phenylalanine to tyrosine
- Arises from a single base change in 5' splice site of phenylalanine hydroxylase gene

20

HAT

- Histone acetyltranferases= acetylate lysine residues in histones
- decreases net positive charge of histone & loosens interaction with negatively charged DNA
- ACTIVATE transcription

21

HDAC

-Histone deacetylases
-Remove acetyl grouops
-INHIBIT transcription

22

DNA Methylation

-DNA can be methylated on cytosine
-Attracts HDACs
- INHIBITS transcription

23

Helix-turn-Helix Protein

- Alpha helix, short amino acid chain, alpha-helix
- Side chains close to the C-terminal of helices binds DNA
- E.g. Homeobox proteins

24

Zinc Finger Protein

- Contain zinc as a structural element
- Alpha-helices bind DNA
- E.g. glucocorticoid receptor

25

Leucine Zipper Proteins

- Form dimers with two alpha-helices joined to form a coiled coil
- E.g. Fos & Jun

26

How do DNA-binding proteins regulate transcription?

- Act as nucleation sites for more proteins
- Recruit HATs, HDACs or chromatin remodeling complexes to DNA

27

How is transcription of the LDL-receptor gene enhanced in response to low cholesterol?

-Promoter region for LDL receptor gene contains SRE-1 (sterol responsive element-1)
- low cholesterol, SREBP-1a (sterol responsive element binding protein-1a) enter the nucleus and binds SRE-1
- Recurits HAT
- Chromatin relaxes and transcription of LDL-receptor increased

28

How does cortisol regulate transcription?

See Diagram

29

How do the thyroid hormone receptor and retinoid X receptor (RXR) act together to regulate transcription in response to thyroid hormomne?

See Diagram

30

What are the roles of CREB & CBP in protein kinase A mediated transcriptional control?

See Diagram