More Eukaryotic Regulation Flashcards
1
Q
epigenetic modifications
A
- slows or speed up transcription
- study of the changes in gene expression that occur without changes in the DNA sequence
- changes are reversible but sometimes stable and heritable
- epigenetic patterns remain in life
2
Q
DNA methylation
A
- slows transcription
- catalyzed by DNA methyltransferase
- methyl is added to 5’ carbon of cytosine
- occurs in regions rich in CpG islands
3
Q
heritability of methylation
A
- heritable since it is a chemical modification of a DNA nucleotide
- in DNA replication, the parent strand retains its methyl groups and a maintenance methylase catalyzes 5-methylcytosine formation in the new strand
4
Q
demethylase
A
- DNA methylation is reversible
- demethylase catalyzes the removal of methyl groups
- methylation patterns in the genome change through development, activating and deactivating genes accordingly
5
Q
methylation as regulation
A
- methylation in or around promoters downregulates expression
- methyl groups in promoters attract transcription repressor proteins
6
Q
improper DNA methylation
A
can lead to pathology
oncogenes may be incorrectly activated by improper methylation
tumor suppressor gene may be incorrectly silenced by improper methylation
7
Q
chromatin remodeling
A
acts above the DNA base pair level
involves DNA packaged with histone proteins to form a nucleosome
8
Q
histone acetylation
A
- increases transcription rate
- histone acetyltransferase adds acetyl groups onto the histone tails in order to decrease the positive charge
- histone interaction with DNA decreases and unravels more easily
9
Q
histone deacetylation
A
- histone deacetylase removes acetyl groups from histone tails
- causes histones to condense more tightly around the DNA, decreasing transcription
- in some cancers, genes that block cell division are excessively deacetylated
10
Q
gene activation with histone modification
A
- gene activity is determined by complex patterns of histone modification
- histone can be phosphorylated and methylated
11
Q
chromosomal epigenetics
A
- large regions or whole chromosomes may have distinct patterns of DNA methylation
euchromatin: diffuse, light-staining = transcribed DNA
heterochromatin: condensed, dark-staining = untranscribed DNA
12
Q
honeybees
A
- female honey bees all have the same genetic makeup
- royal jelly fed to queen bees induces phenotypic changes and alters expression
- ENVIRONMENTAL FACTORS INDUCE EPIGENETIC CHANGES
13
Q
inactivated X-chromosome
A
- in mammals, the level of X-chromosome transcription is the same in XX and XY genotypes
- a random X chromosome is inactivated during development
- inactivated X chromosome presents as a Barr body in heterochromatin
- DNA in Barr body is heavily methylated
14
Q
Xist
A
- interfering RNA
- transcribed from the inactivated X-chromosome and binds to the chromosome, inducing methylation
- only gene transcribed
15
Q
interfering RNA (miRNA and siRNA)
A
- transcribed but not translated
- double-stranded RNA is cut into little fragments by Dicer
- forms RISC with other proteins to bind to mRNA and prevent translation
16
Q
miRNA
A
- transcribed from the genome and forms a secondary structure
- regulated in coordination with the target gene
- targets a wide range of genes
17
Q
siRNA
A
- already incorporated into the genome
- prevents expression by targeting itself
18
Q
translation-blocking repressor proteins
A
- silences mRNA
- generally respond to an environmental circumstance
19
Q
ferritin repressor protein
A
- prevents ferritin from being made made when unnecessary
- binds to ferritin mRNA
- inactivated when Fe2+ induces a conformational shape changes and allows mRNA to be translated
