Ch. 18

Front 1

acetylation (def)

Back 1

Theaddition of an acetyl group, CHCO3, to an organic molecule. The acetylation of histones makes chromatinless compact so that transcription can occur.

Front 2

Chromatin (Def)

Back 2

Thecomplex of DNA and proteins that makes up eukaryotic chromosomes.

Front 3

Deacetylation (DEF)

Back 3

The removal of an acetyl group, CHCO3, from anorganic molecule. The deacetylation ofhistones makes chromatin more compact so that transcription is prevented.

Front 4

DNA methylation (def)

Back 4

Thepresence of methyl groups on the DNA bases (usually cytosine). Methylation can affect transcription,typically lowering the amount

Front 5

Epigenetic inheritance (def)

Back 5

: Inheritance of traits transmitted bymechanisms not directly involving the nucleotide sequence of a genome

Front 6

Gene expression (def)

Back 6

The process by which information encoded in DNA directs thesynthesis of proteins.

Front 7

Histone (def)

Back 7

Asmall protein with a high proportion of positively charged amino acids thatbinds to the negatively charged DNA and plays a key role in chromatinstructure.

Front 8

Gene regulation in Eukaryotes:

Back 8

· Eukaryotic DNA is packaged tightly intochromatin by wrapping around histone proteins

Front 9

Histonetails are

Back 9

positivelycharged; attracted to negatively charged DNA

Front 10

Tightwrapping prevents

Back 10

genetranscription

Front 11

Telemereand centromere regions (heterochromatin) always tightly wrapped preventing

Back 11

genetranscription in those areas

Front 12

· Chromatin can be modified by:

Back 12

1. Acetylationof histones

2.Methylationof DNA

Front 13

1. Acetylationof histones:

Back 13

(addingof acetyl groups) Lessens attraction between histones and DNA: Transcription occurs

Front 14

2. Methylationof DNA:

Back 14

(addingof methyl groups) Typically prevents transcription

Front 15

Methylationpatterns can be altered during:

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anorganism’s lifetime thus possibly changing gene expression (epigeneticinheritance)

Front 16

Methylationpatterns can be passed on to:

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offspring

Front 17

Epigeneticscan have possibly profound implications for:

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health and influence of environment on anorganism’s gene expression

Front 18

Whatare some ways eukaryotes control gene expression through chromatin structure?

Back 18

Eukaryoteshave their linear DNA strands wrapped around histone proteins formingnucleosomes. The DNA and proteins togetherform chromatin. If the chromatin istightly packed together in areas, the transcription of genes in those areaswill be turned off or reduced. If thechromatin is more loosely packed, transcription can occur. The denseness ofchromatin can be influenced in many ways, one of which is by acetylation of thehistone proteins. The tails of histonesare positively charged which attracts them to the negatively charged DNA. When this attraction is strong, the chromatinis tightly packed and transcription is less. The acetylation makes the histones less positive so the attraction tothe DNA is weakened, thus making the chromatin less packed and transcriptioncan occur. Another way to regulatetranscription is to chemically modify the DNA itself by adding methylgroups. Typically, this methylation willreduce transcription.5