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Genetics > Epigenetics 27-33 > Flashcards

Epigenetics 27-33 Flashcards

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1
Q

What is Epigenetics?

A

phenotypic variation —> variation in gene expression

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2
Q

What does gene expression changes mean?

A

gene expression change = chromatin structure change

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3
Q

What are some characteristics of Chromatin Structure?

A
  • cell division stabilized (mitosis)
  • passed on (meiosis)
  • influenced by environment
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4
Q

What is DNA Modification?

A

Methylation of nucleotide bases (mostly cytosine)
—– CpG dinucleotides
—– both strands of DNA modified
Lowers gene expression

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5
Q

What is Histone Modification?

A
  • Methylation, phosphorylation, acetylation, ubiquitination
  • affects binding to DNA
  • some lower some higher gene expression
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6
Q

How is level of DNA Methylation maintained after DNA replication?

A

-both DNA molecules are hemimethylated
—-methylated on 1 DNA strand
—-
-special methyltransferase enzymes recognize hemimethylated DNA

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7
Q

Does DNA Methylation increase or decrease gene expression?

A

Decrease

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8
Q

What are the 2 ways DNA methylation down-regulates gene expression?

A
  1. Methyl group in major groove prevents binding of proteins that stimulate transcription
  2. creates binding site for histone deacetylase enzymes
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9
Q

Why are transcription factors important?

A

They turn on gene expression

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10
Q

What are histone deacetylase enzymes do?

A

remove acetyl groups from histone proteins
— histones bind DNA more tightly
— chromatin structure is more condensed
— gene expression downregulated

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11
Q

What are characteristics of Histone modifications?

A
  • Heritable
  • positively charged tails
    — groups of amino acids at end of histones
    — wraps around DNA & interact w/phosphates in backbone
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12
Q

What does Histone Acetylation do?

A

-masks positive charges
-binding to DNA weaker
-chromatin structure less condensed
-stimulates gene expression higher

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13
Q

What does Histone Methylation do?

A

-creates binding sites for transcription factors
- can “mark” an area for increased or decreased gene expression
—–How? –> specific amino acids in certain histones

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14
Q

Is Histone modification heritable?

A

Yes

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15
Q

What are some examples of Epigenetics?

A
  1. Queen v.s. worker bees
  2. X-inactivation
  3. Genomic imprinting
  4. Behavioral epigenetics
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16
Q

Explain DNA Methylation in Honeybees

A
  • Queen and worker bees develop from genetically identical eggs.
  • Differences are caused by changes in gene expression (Diet)
  • Queen is the only one that eats royal jelly
    -royal jelly = Dnmt3 gene repressed = Less methylation= increased gene expression
17
Q

Explain X-Inactivation

A

-random event early in development
- stable changes in gene expression
- daughter cells after mitosis
- histone modification important

18
Q

What are the important genes of X-inactivation?

A

X-ist = X-inactivation specific transcript

important for keeping one X activated:
Tsix
Jpx
Xite

19
Q

What is Xist gene?

A

-encodes long RNA that does not code for protein
- binds X-chromosome from which it was made
-attracts protein complexes (PRC2:PRC1)
—methylate histones to turn off gene expression
—“epigenetic mark” for repressed gene expression

20
Q

What is Tsix gene?

A
  • Keeps ative X from being inactiviated
  • encodes long RNA that does not code for protein
    — anti-sense to Xist RNA
    — prevents Xist expression/function on activated X
21
Q

What is Jpx gene?

A

-encodes long RNA that does not code for protein
- stimulates synthesis of Xist on inactive chromosome

22
Q

What is Xite gene?

A

-encodes long RNA that does not code for protein
- sustains Tsix expression on active X chromosome

23
Q

Explain Genomic Imprinting

A

-expression affected by whether mom or dad
- results is autosomal traits that show different results for reciprocal crosses
- clusters 3-12
—encode proteins and noncoding RNAs
—chromatin modifications differ
- genetic conflict hypothesis attempts to explain
hinny vs mule

Genetics (6 decks)

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