Exam 2 - Lecture 7 (pre- and post- transcriptional reg)

Question 1

Epigenetic

Answer 1

Study of changes in gene expressions that occur without changes in the DNA sequences
- Doesn’t need a mutation to change whether or not expression will occur
- This allows it to be reversible

Question 2

DNA methylation

Answer 2

slows transcription
- Regulates expression

Question 3

CpG island

Answer 3

Regions rich in C and G

Question 4

methyltransferase

Answer 4

Enzyme catalyzing initial methylation and its maintenance through replication
- Acts during DNA replication to keep methylation pattern

Question 5

maintenance methylase

Answer 5

• the maintenance methylase will catalyze 5-methylcytosine formation in the new strand
• Adds methyl groups to the new daughter strand to match the parent strand

Question 6

histone methylation

Answer 6

• It may inactivate genes by decreasing the negative charge on histone proteins.
• The effects depend on the amino acids within the histone that are involved

Question 7

histone acetylation/deacetylation

Answer 7

Acetylation: Increases transcription rate
- Activates transcription by reducing how strongly the histones interact with DNA
Deacetylation: decreases transcription rate

Question 8

chromatin remodeling

Answer 8

Involves DNA interaction with proteins
Changing chemical properties of histones:
- Increasing or decreasing charge with methyl groups
- Increasing or decreasing charge with acetyl groups

Question 9

euchromatin

Answer 9

Diffuse, light-staining; contains DNA that IS transcribed

Question 10

heterochromatin

Answer 10

Condensed, dark-staining, contains genes NOT transcribed

Question 11

Barr Body

Answer 11

Dense heterochromatin, attached to the side of the nuclear envelope

Question 12

interfering RNA

Answer 12

Prevents transcription of the rest of the chromosome
- Transcribed but never translated

Question 13

Xist gene

Answer 13

only gene on the inactive (x) chromosome to be transcribed
- RNA transcribed from Xist (x inactivation-specific transcript) binds to the chromosome and increases DNA methylation

Question 14

miRNA

Answer 14

Transcribed from the genome in both eukaryotes and prokaryotes
- Target certain genes elsewhere in the genome and silence that RNA
- Often regulated in coordination with their target genes

Question 15

siRNA

Answer 15

Originated as viral RNA (from ancestors) or from transcription of transposons
- Evolved to prevent viral RNAs from being expressed
- siRNAs prevent their expression by targeting themselves.

Question 16

translation-blocking repressor protein

Answer 16

• Can silence mRNA
  Usually responds to environmental circumstances
  Interrupts expression at the level of translation initiation by preventing mRNAs from being translated