M1-Lecture 2 Flashcards
What leaves a chemical “signature” on the genes that determines whether & how the genes are expressed.
Experiences
Different genotypes respond to environmental stimulus differently? T/F
TRUE
The three components that make up a phenotype:
Epigenetics, Environment, and Genetics.
Give example of SNPs:
SNP mutation resulting in gene variants that can influence sensitivity to one’s environment.
Example of Epigenetics:
microRNA and ncRNA
CpG methylation
Histone modification
Example of environment:
Nutrition, toxins, drugs, pathogens
Embryonic stem cell divisions:
Mesoderm: middle layer
Endoderm: Internal layer
Ectoderm: External layer
How did the cells in our body become different & why do they stay like that?
Once specialized, the changes are permanent.
DNA not always in chromosome form but open? T/F
TRUE
Modifying the histone will expose the DNA? T/F
TRUE
What are the factors that affect epigenetic mechanisms:
Development (utero, childhood)
Environmental chemicals
Drugs/pharmaceuticals
Aging
Diet
Mention a few epigenetic modifications:
DNA methylation
Histone modification
Chromatic accessibility
Non-coding RNA regulation
What is an epigenetic factor found in some dietary sources:
Methyl group
DNA methylation function:
Can tag DNA and activate or repress genes.
Blank are proteins around which DNA can wind for compaction and gene regulation.
Histones
What alters the extent to which DNA is wrapped around histones & availability of genes in DNA to be activated?
Epigenetic factors (which can give rise to health endpoints).
For instance, increased histone acetylation generally leads to a more open chromatin structure, facilitating gene expression, while DNA methylation typically silences genes by promoting a closed chromatin configuration.
Biological dogma states that genetics regulates all inherited traits across generations, & epigenetic modifications are reset upon passage of germ line? T/F
TRUE
What is responsible for the functional use & stability of the genetic info our chromosomes hold & connects genotype to phenotype.
Epigenome
Epigenetic inheritance occurs through meiosis and several generations, including trans-generational? T/F
TRUE
The nucleosomes of DNA and histones are organized into what:
Chromatin
Change to the structure of chromatin influences gene expression: T/F
TRUE
Epigenetic modifications - when is a gene “switched on”:
Active “open” chromatin
Unmethylated cytosines [bases in DNA] (white circles)
Acetylated histones (adding acetyl group to lysine residues on histone proteins) reduces + charge on histones for relaxed and open chromatin structure for gene transcription.
Epigenetic modifications: when is a gene “switched off”
Silent (condensed) chromatin
Methylated cytosines (red circles)
Deacetylated histones
Types of histone modifications:
Acetylation
Methylation
Sumoylation
Phosphorylation
Ubiquitination
Define the types of histone modification:
Acetylation: adding acetyl group to lysine (found in histone tails) residues on histones (makes chromatin open)
Methylation: addition of methyl groups to lysine/arginine (found in the tails of histone) residues on H (activate/repress gene expression) Note: depends number of methyl added & specific residues affected.
Phosphorylation: adding phosphate group to serine, threonine, or tyrosine residues on H, affecting chromatin structure, gene e. common in cell divi. & DNA damage repair.
Ubiquitination: addition to H. influence chromatin s. & gene expression, histone degradation or altering chromatin dynamics.
Sumoylation: addition of SUMO to H, impact chromatin structure & gene expression, gene silencing.
In condensed nucleosomes, histones are methylated and unacetylated. T/F
TRUE
Uncondensed nucleosomes, histones are unmethylated & acetylated. T/F
TRUE
Active vs. inactive regions of chromatin:
Active chromatin: unmethylated DNA & acetylated histones.
Inactive chromatin:
Methylated DNA & deacetylaed histones
An epigenetic tag (methylated vs. unmethylated) is placed on targeted DNA, marking it with a special status that activated or silences genes? T/F
TRUE
DNA methylation or unmethylation are reversible modifications and benefit?
Specific genes can be expressed or silenced genes based on deve. or biochemical cues, such as changes in hormone levels, dietary components or drug exposures.
What does histone code hypothesis state:
Activity of chromatin region depends on degree of chemical modification of histone tailes.
What enzymes place acetyl groups on histone?
Acetyltransferases
What enzyme removes acetyl groups from histones?
histone deacetylases
Methyl groups are placed on DNA by what?
DNA methyl transferases
Demethylation of DNA can either be passive (through replication process) or active or both? T/F
TRUE
Methylated promoters & enhancers keep genes inactive? T/F
TRUE