Lec. 23: Regulation of Gene expression

Question 1

Promoter

Answer 1

The region in which transcription is initiated and includes the TATA box

Question 2

Transcription factors

Answer 2

Bind to the promoter and control elements

Can be activators OR repressors

Question 3

Differences between msot cell types are due to:

Answer 3

Differential gene expression.

Each stage of gene expression is a potential control point for gene expression and ultimately protein function

Question 4

Chromatin

Answer 4

complex of DNA and protein and found in the nucleus of eukaryotic cells

Question 5

Histones

Answer 5

proteins that are responsible for the first level of DNA packing in chromatin

help compact and condense DNA (chromatin) to fit in the nucleus

Question 6

Nucleosomes

Answer 6

a segment of DNA wrapped around 8 histone proteins

Question 7

Euchromatin

Answer 7

loosely packed cromatin

typically during interphase

Question 8

Heterochromatin

Answer 8

During interphase and prior to mitos: a few regions of chromatin (centromeres and telomeres) are highly condensed

Difficult for cell to express genetic information coded in heterochromatin
- Most condensesd during metaphase in which you can see the chromosomes

Question 9

Histone Acetylation

Answer 9

acetyl groups (- charge) are attached to a positively charged lysine in the histole tails which loosens chromatin structure and promoting initiation of transcription

Notes:
- when acetyl neutralizes lysine=chromatin relaxes
- DNA (-) charge is attracted to + charge histone tails containing lysine which causes the compacting of DNA
- Acetyl can recognize lysine residue

Question 10

DNA Methylation

Answer 10

The addition of a methyl group (CH3) on cytosine residues in promoter region of DNA which:
- inactivates DNA
- long term inactivation
- mechanism underlying genomic imprinting
- can be passed can be onto offspring

Question 11

Transcription factors

Answer 11

Bind to the promoter and control elements and guides RNA polymerase to initiate transcription by binding to the promoter

• high levels of interactions with transcription factors=high levels of transcription of genes

Question 12

Activators and Repressors

Answer 12

Activators are proteins that bind to an enhancer and stimulate transcription of a gene
Repressors bind to control elements to block transcription of a gene

Both transcription factors

Activators bind DNA and activate transcription

Question 13

Steps to form Transcription initiation complex

Answer 13

1. Activators proteins bind to enhancer
2. DNA bending protein binds and transcription factors bind to promoter which recruit RNA Polymerase II
3. Formation of active transcription initiation complex

Question 14

Cell-Type specific Transcription

Answer 14

The particular combination of control elements in an enhancer region and available activators determine the gene that is expressed

Question 15

Alternative RNA splicing

Answer 15

RNA transcript includes introns and exons. Cells can include which exon is included in the messenger RNA.
Allows a singular gene to code for multiple mRNA=different proteins

allows humans to have much less genes/genetic information than other eukaryotes like an onion LOL

Question 16

mRNA degradation

Answer 16

• shortening of polyA Tail and removal of 5’ cap
• nuclease chew up mRNA
• half life in bacteria is much shorter than eukaryotes because bacteria has no cap and tail

Question 17

initiation of translation

Answer 17

• can be blocked by regulatory proteins
  -regulator proteins bind 5’ UTR
  prevents attachment of ribosomes

Question 18

Protein processing and degradation

Answer 18

Proteasomes are giant protein complexes that bind protein molecules and degrade them