Lecture 3 Flashcards
(29 cards)
What are non-genetic factors that may cause or contribute to genetic disease?
Environmental factors, lifestyle choices, and chemical modifications
Non-genetic factors may include pollution, diet, and stress.
What is epigenetics?
The study of chemical modifications of DNA that regulate gene expression without altering the DNA sequence
This includes modifications like DNA methylation and histone modification.
What is epigenomics?
The study of chemical modifications of the entire genome that affect gene expression
Epigenomics examines broader genomic changes compared to epigenetics, which focuses on individual genes.
What are the two forms of chromatin?
- Euchromatin (loosely packed, transcriptionally active)
- Heterochromatin (densely packed, transcriptionally inactive)
Chromatin structure influences gene accessibility and expression.
What is the role of histones in DNA packaging?
Histones are special proteins that package DNA into chromatin, facilitating DNA compaction
Each nucleosome consists of a core of histone proteins around which DNA is wrapped.
What is the significance of histone tail modifications?
They regulate gene expression by altering chromatin structure or recruiting other proteins
Modifications include acetylation, methylation, phosphorylation, ubiquitylation, and sumoylation.
What happens during histone acetylation?
The addition of acetyl groups makes genes accessible for transcription by relaxing chromatin structure
Acetylation neutralizes positive charges on histones, reducing their binding to negatively charged DNA.
What is the effect of histone methylation?
Methylation can either increase or decrease transcription depending on the specific amino acids modified
Methylation generally leads to tighter packing of nucleosomes, inhibiting transcription.
How does DNA methylation inhibit gene expression?
Methyl groups block transcription factors and RNA polymerase from accessing the promoter
Methyl-binding proteins can also recruit enzymes that alter histone acetylation.
Which bases are typically methylated in DNA?
Cytosine bases in CpG dinucleotides
Methylation patterns can distinguish between active and inactive genes.
What is the relationship between DNA methylation and environmental factors?
Environmental factors can alter DNA methylation patterns, affecting gene expression
Factors include smoking, diet, and stress, which may lead to diseases.
What is the consequence of increased DNA methylation?
It may lead to point mutations due to changes from cytosine to thymine
Methylated cytosines are more prone to deamination.
True or False: Histone acetylation and methylation have the same effect on gene expression.
False
Acetylation generally leads to active transcription while methylation usually results in inactivity.
What are the four mechanisms that regulate chromatin structure?
- Posttranslational modifications of histone tails
- Histone variants
- Histone chaperones
- ATP-dependent complexes
These mechanisms work together to control DNA accessibility.
What is the effect of environmental exposures on gene expression?
They can lead to inappropriate modulation of gene expression through epigenetic changes
Examples include effects from toxins, medications, and lifestyle choices.
Fill in the blank: The addition of a methyl group to the DNA base cytosine is known as _______.
DNA methylation
This modification typically leads to gene inactivation.
What is the role of methyl-binding proteins in relation to DNA methylation?
They bind to methylated DNA and block transcription factor access to promoters
MBPs can also recruit enzymes that further modify histones.
What is the consequence of abnormal gene expression due to dysregulation of epigenetic modifications?
It can lead to diseases
Examples include cancer and other genetic disorders.
What is the result of deamination of cytosine bases?
They turn into a thymine base
Deamination can lead to changes in base-pairing properties, impacting DNA integrity.
What types of radiation can chemically modify T base?
X-ray and UV radiation
These modifications can affect base-pairing with G base.
What happens to nucleotide bases when amino groups are deaminated?
They turn into keto groups
Examples include: A → HX (hypoxanthine), G → X (xanthine), C → U (in DNA).
What is ethylguanine (eG) and what does it pair with?
It is a chemically modified DNA base that pairs with T
Chemicals in cleaning agents can lead to the formation of eG.
What are the two components that guide gene expression?
Epigenetic marks and DNA sequence
These signals help regulate genes at the right time, place, and amounts.
What is a key characteristic of gene networks?
Almost all genes are part of gene networks
A single gene can influence the activity of multiple other genes.
