Genetics Week 12

Activator

responsible for much of the variation in levels of transcription of different genes. recruit RNA pol II to basal promoters, also recruit coactivators to open chromatin structure by displacing nucleosomes

Angelman syndrome

syndrome occurs when deletion is inherited from the mother

Barr body

example of facultative heterochromatin, inactive X-chromosome appear as darkly stained heterochromatin masses observed in somatic cells at interphase

Basal factors

bind to promoters of protein coding genes

Coactivators

recruited to displace nucleosomes and open chromatin structure

Corepressor

two alternating functions, prevent RNA pol II complex from binding the promoter, modify histones to close chromatin structure

Dicer

processes pre-miRNA to a mature duplex miRNA

Dosage compensation

part of Barr bodies that overcompensate so that X-linked genes in XX and XY individuals are expressed at the same level

Drosha

excises stem-loop from primary miRNA to generate pre-miRNA

Enhancer

DNA sequence in Eukaryotes that cab be far from the gene, repress the basal level of transcription

Epigenetics

DNA sequence in genes in not the only carrier of genetic information, heritable self-perpetuation changes in gene expression not caused by base pair sequence changes. Epigenetic factors determine whether a gene is “on” or “off”

Genomic Imprinting

phenomenon where expression of an allele depends on the parent that transmits it

Insulator

sequences located between an enhancer and a promoter, block access to the promoter, also organize genomic DNA into loops

Inter-generational epigenetic inheritance

environmentally induced trait (not bp mutation) that is displayed only in the child or child and grandchild of an originally exposed female or the child of an exposed male 

Mediator

required to transcribe many eukaryotic genes, a complex of more than 20 proteins, bridges RNA Pol II at the promoter and activator or repressor proteins at the enhancer

MiRNA

micro RNA’s, transcribed by RNA pol II, block mRNA translation and destabilize mRNA’s

PiRNA

piwi interacting RNA’s, target transposable element transcripts and promoters, degrade transposable element mRNA, facilitate histone modifications that inhibit transposable element transcription

Prader Willi syndrome

when deletion is inherited form the father

Pre-miRNA

formed by drosha and then processed by dicer to a mature duplex miRNA

Repressor

suppress transcription initiation by recruiting corepressors

RISC

one strand is incorporated into miRNA induced silencing complex

SiRNA

small interfering RNA’s, block translation/destabilize mRNA’s recruit histone modifying enzymes to DNA, resulting in heterochromatin formation
TATA binding protein

TBP-associated factor

proteins that associate with the TATA-binding protein in transcription initiation.

Transcription factor

sequence specific DNA binding proteins, bind to promoters and enhancers, recruit other proteins to influence transcription, 3 kinds: basal factor, activator, repressor

Trans-generational epigenetic inheritance

environmentally induced trait (not a bp mutation) spearing in descendants of an individual whose germ line was not directly exposed to the stimulus

X-inactivation

initiated by expression of the Xist gene

XIC

X-chromosome inactivation center, hotbed of functional long non-coding RNAs in eutherian mammals, help orchestrate the epigenetic transcriptional states of the two X-chromosomes in females as well as of the single X-chromosome in males.

Xist

large non-coding, cis acting regulatory RNA, binds to X-chromosome that it was expressed from, initiates histone modifications that result in heterochromatin formation

NcRNA

functional RNA molecule that is not translated into a protein. Ex: rRNA tRNA. etc

Alternative Splicing

process of selecting different combinations of splice sites within a messenger RNA precursor (pre-mRNA) to produce variably spliced mRNAs.