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Biology unit 5 > epigeneitcs > Flashcards

epigeneitcs Flashcards

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1
Q

What are epigenetic changes

A

Chemical modifications to chromosomes

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2
Q

What happens in epigenetic changes

A

Chemical tags are added onto DNA or associated proteins called histones

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3
Q

When does epigenetic changes occur

A

During development of an organism and by environmental factors

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4
Q

Define epigenetics

A

Changes in DNA that alter the expression of genes without changing the base sequence of DNA itself. These changes can be caused by environmental factors and are heritable

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5
Q

What is the epigenome of a cell

A

The chemical tags attached to the DNA and histones. Lifetime accumulation of signals that the cel has received from the environment

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6
Q

How are epigenetic changes able to regulate transcription

A

By remodelling chromatin (complex formed from DNA and histones)

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7
Q

What do signals from the environment do to the chromatin

A

Cause chemical tags to be added to histones or the DNA, changing how tightly packed the chromatin is

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8
Q

What occurs when chromatin is too tightly packed

A

The DNA wrapped around it may not be accessible to RNA polymerase and transcription factors. This means RNA polymerase cannot bind to the DNA and transcription cant occur and the gene will not be expressed

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9
Q

What is tightly packed chromatin called

A

heterochromatin

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10
Q

What happens when chromatin is loosely packed

A

The DNA is exposed and is accessible to RNA polymerase and transcription factors and the gene will be transcribed

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11
Q

What is loosely packed chromatin called

A

euchromatin

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12
Q

How do chemical tags control which genes are switched on or off

A

By regulating the formation of euchromatin or heterochromatin

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13
Q

What is one method used to regulate gene expression

A

Methylation of DNA

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14
Q

What occurs in methylation

A

Methyl groups are added to DNA at specific locations called CpG sites

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15
Q

What is a CpG site

A

Where cytosine is found next to guanine in the DNA chain

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16
Q

How are methyl groups added to the cytosine bas

A

By an enzyme called DNA methyltransferase

17
Q

What does DNA methylation always do to transcription

A

Inhibits it

18
Q

What is the first way DNA methylation prevents transcription

A

Transcription factors may no longer be able to bind to the DNA, there for RNA polymerase cant bind

19
Q

What is the second way DNA methylation prevents transcription

A

The methyl groups may attract proteins that condense the chromatin, making the genes inaccessible for transcription

20
Q

What process removes Methyl groups

A

Demethylation

21
Q

What does demethylation do

A

The chromatin becomes more loosely packed and the genes are more accessible for transcription

22
Q

What is another method used to regulate gene expression

A

Histone modification (adding chemical tags to histone proteins)

23
Q

What is accetylation

A

The process of adding an acetyl group to histone proteins

24
Q

What are acetyle groups added to

A

lysine amino acids found in the histone protein

25
Q

How are acetyle groups added to lysine amino acids

A

By acetyl-coenzyme A

26
Q

What does accetylation do

A

Neutralises the positive charge of the lysine, reducing the attraction between the DNA and the histones

27
Q

What does accetylation do to the chromatin

A

Makes it more loosely packaged, forming euchromatin where genes are accessible for transcription

28
Q

What happens in deacetylation

A

Reverse reaction where an acetyl group is removed from the lysine in the histone proteins

29
Q

What does deacetylation do to chromatin

A

Makes it more compact which forms heterochromatin, which prevents genes from being transcribed

30
Q

What is the other way histones can be modified

A

Methylation

31
Q

What happens in methylation

A

Methyl group is added to the amino acid lysine

32
Q

What does methylation do to chromatin

A

Condenses it to form heterochromatin which silences genes

33
Q

What does histone methylation play an important role in

A

Silencing one of the X chromosomes in female mammals

34
Q

How are epigenetic changes made to chromosomes

A

Adding chemical tags to histones

Biology unit 5 (49 decks)

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