Bio 1002: Cycle 11 (Epigenetics)
Questions and All Correct Answers.
What are epigenetics? - Answer The study of changes in the gene expression caused by
mechanisms other than charges in the underlying DNA sequence. Genes can be "tagged" by our
experiences- this is a dynamic process that is not random. These tags can be inherited by the
offspring (transgenerational epigenetic inheritance).
What is DNA methylation? - Answer DNA methylation is the addition of methyl groups (-CH3)
to certain positions on cytosines, at sites such as [5'--CpG--3']/[3'--GpC--] (both strands). Not all
cystosines are methylated; however, promoters are highly to get methylated. It's done by DNA
methyltransferase (DNM).
What are the consequences of methylation? - Answer It inactivates transcription since the
transcription factors (that signal to RNA polymerase) can't recognize the promoter anymore.
Demethylation activates transcription.
↑ Methylation = ↓ Transcription
↓ Methylation (demethylation) = ↑ Transcription
What is histone modification? - Answer When acetyl groups are added or removed to
histone tails (beginning and ends to the polypeptide chain histone); acetylated or deacetylated,
respectfully.
↑ Acetylation = ↑ Transcription
↓ Acetylation (deacetylation) = ↓ Transcription
What is the heterochromatin state? - Answer When there's no acetyl groups on the histone
tail. This makes the DNA inaccesible and inactivates the gene, since the genes are wound up
around the histone.
What is the euchromatin state? - Answer When there's acetyl groups present on the histone
tail. The acetyl binds to listine (+ charge), so it's not tightly bound anymore. This makes the DNA
accesible and activates the genes.
What is "de novo" DNA methylation? - Answer The DNA has yet to be methylated, and it's
done by DNMT3A and DNMT3B. After DNA replication, only one stand (one each copy) is
methylated, so DNA methylation of maintenance happens to make both strands match.
What id DNA methylation of maintenance? - Answer The un-methylated strand of DNA after
replication is methylated by DNMT1 to make both strands match.
Questions and All Correct Answers.
What are epigenetics? - Answer The study of changes in the gene expression caused by
mechanisms other than charges in the underlying DNA sequence. Genes can be "tagged" by our
experiences- this is a dynamic process that is not random. These tags can be inherited by the
offspring (transgenerational epigenetic inheritance).
What is DNA methylation? - Answer DNA methylation is the addition of methyl groups (-CH3)
to certain positions on cytosines, at sites such as [5'--CpG--3']/[3'--GpC--] (both strands). Not all
cystosines are methylated; however, promoters are highly to get methylated. It's done by DNA
methyltransferase (DNM).
What are the consequences of methylation? - Answer It inactivates transcription since the
transcription factors (that signal to RNA polymerase) can't recognize the promoter anymore.
Demethylation activates transcription.
↑ Methylation = ↓ Transcription
↓ Methylation (demethylation) = ↑ Transcription
What is histone modification? - Answer When acetyl groups are added or removed to
histone tails (beginning and ends to the polypeptide chain histone); acetylated or deacetylated,
respectfully.
↑ Acetylation = ↑ Transcription
↓ Acetylation (deacetylation) = ↓ Transcription
What is the heterochromatin state? - Answer When there's no acetyl groups on the histone
tail. This makes the DNA inaccesible and inactivates the gene, since the genes are wound up
around the histone.
What is the euchromatin state? - Answer When there's acetyl groups present on the histone
tail. The acetyl binds to listine (+ charge), so it's not tightly bound anymore. This makes the DNA
accesible and activates the genes.
What is "de novo" DNA methylation? - Answer The DNA has yet to be methylated, and it's
done by DNMT3A and DNMT3B. After DNA replication, only one stand (one each copy) is
methylated, so DNA methylation of maintenance happens to make both strands match.
What id DNA methylation of maintenance? - Answer The un-methylated strand of DNA after
replication is methylated by DNMT1 to make both strands match.
