Exam 5 - Remaining Flashcards
(25 cards)
Eukaryotic Gene Regulation Compared to Prokaryotic
Greater amount of DNA that is associated with histones and other proteins
mRNAs must be spliced, capped, and polyadenylated prior to transport from nucleus
Genes on numerous chromosomes are enclosed in a double membrane nucleus
mRNAs have wide range of half-lives
Modulation of mRNA translation, protein processing, modification, and degradation
Core Promoter Structure in Eukaryotes
Comprised of:
-Initiator (Inr)
-TATA-box
-TFiiB recognition element (BRE)
-Downstream promotor element (DPE)
-Motif ten element (MTE)
Function of MTIIA protein
Protein that binds to heavy metals and protects cells from toxic effects
Protects cells from oxidative stress
Expressed in low levels in all cells
Transcribed at high levels when exposed to heavy metals
Transcriptional Regulation of MTIIA
–Transcription regulatory proteins
–Target cis-acting sites of genes regulating expression
–Activators increase transcription initiation
–Repressors decrease transcription initiation
Basal transcription regulated by:
TFIID (and other basal transcription factors)
SP1 – binds at proximal-promoter element GC (contains G-C base pairing)
Modulation of transcription by TF binding to enhancers
AP1, AP2, AP4 – regulated by external growth signals
High levels of MTIIA transcription stimulated by
Heavy-metal toxicity (MTF-1): Heavy metals bind to MTF-1 and induces a conformation change to allow TF function
Stress (glucocorticoid receptor): Stress causes vertebrates to secrete glucocorticoid
Glucocorticoid binds receptor and induces a conformation change to allow TF function
Transcription repressed by:
PZ120 – binds over transcriptional start site
epigenetic trait
a stable, mitotically and meiotically heritable phenotype that results from changes in gene expression without alterations in the D N A sequence
Epigenetics
the study of the ways in which these changes alter cell- and tissue-specific patterns of gene expression
epigenome
refers to the epigenetic state of a cell
During its life span, an organism has one genome, but this genome can be modified in diverse cell types at different times to produce many epigenomes
Epigenetics has been implicated in:
Progressive restriction of gene expression during development
Allele-specific expression in gene imprinting
Environment genome interactions during prenatal development that affect adult phenotypes
Monoallelic expression (MAE)
Only one allele is transcribed, while the other allele is transcriptionally silent
There are three major classes of MAE
Parent-of-Origin Monoallelic Expression: Imprinting
Random Monoallelic Expression: Inactivation of the X Chromosome
Random Monoallelic Expression of Autosomal Genes
Igf2 Imprinting
Different expressions based on what you get from chromosomes from each parent. Both parents have the genes but only one gets expressed
Established in the sperm and the egg prior to fertilization.
You only express IGF2 from your dad and H19 from your mom based on methylation
imprinting is an epigenetic process that can be divided into three stages
1)Establishment of the imprint during gametogenesis
2) Maintenance of the imprint during embryogenesis and in the adult somatic cells
3) Erasure and reestablishment of the imprint in the germ cells
Thus genomic imprinting is permanent in the somatic cells of an animal
Reprogramming in parental germ line
Reprogramming occurs in the parental germ line and in the developing embryo just before implantation
After implantation, differential genomic remethylation recalibrates which maternal and paternal alleles will be inactivated
Beckwith–Weidemann syndrome
Caused by abnormal patterns of DNA methylation resulting in altered patterns of gene expression
Prader-Willi syndrome (PWS)
Reduced motor function
Obesity
Small hands and feet
Involves a small deletion in chromosome 15 from the father
Angelman syndrome (AS)
Hyperactivity and thinness
Unusual seizures
Repetitive symmetrical muscle movements
Mental deficiencies
Involves a small deletion in chromosome 15 from the mother
Epigenetics and Random Inactivation of the X Chromosome
About half of embryonic cells randomly inactivate the maternal X chromosome and the other half inactivate the paternal X chromosome
Effectively silencing almost all the 900 or so genes on whichever homolog is inactivated
Once inactivated, the same X chromosome remains silenced in all cells descended from this progenitor cell
Xic region of the X chromosome: Xist and Tsix
Assisted Reproductive Technologies (ART)
Imprinted genes play major roles in controlling growth during embryonic and prenatal development
External or internal factors that disturb the epigenetic pattern of imprinting or the expression of imprinted genes can have serious phenotypic consequences
In vitro fertilization (IVF) in humans can cause problems with imprinted genes
Environmental Induction of Epigenetic Change
Environmental agents including nutrition, chemicals, and physical factors such as temperature can alter gene expression by affecting the epigenetic state of the genome
Epigenetics and Diet in Mice
The Agouti gene in mice promotes the synthesis of yellow fur pigment; this is called the Avy allele.
Strains of mice carrying the Avy allele show a range of coat colors, from yellow to pseudo-agouti
When pregnant mice were fed a diet that contained chemicals that tend to increase DNA methylation, the offspring tended to have darker fur due to DNA methylation of the Agouti gene
