Basic Principles of Transcription and Translation - Computer ...

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Regulation of Chromatin Structure Genes within highly packed heterochromatin are usually not expressed Chemical modifications to histones and DNA of chromatin influence both chromatin structure and gene expression Histone Modifications In histone acetylation, acetyl groups are attached to positively charged lysines in histone tails This process loosens chromatin structure, thereby promoting the initiation of transcription The addition of methyl groups (methylation) can condense chromatin; the addition of phosphate groups (phosphorylation) next to a methylated amino acid can loosen chromatin The histone code hypothesis proposes that specific combinations of modifications help determine chromatin configuration and influence transcription
Histone tails DNA double helix Amino acids available for chemical modification (a) Histone tails protrude outward from a nucleosome. This is an end view of a nucleosome. The amino acids in the Ntermincal tails are accessible for chemical modification Unacetylated histones Acetylated histones A simple model of histone tails and the effect of histone acetylation. In addition to acetylation histones can undergo several other types of modifications that also help determine the chromatin configuration in a region. (b) Acetylation of histone tails promotes loose chromatin structure that permits transcription. A region of chromatin in which nucleosomes are unacetylated forms a compact structure (left) in which the DNA is not transcribed. When nucleosomes are highly acetylated (right) the chromatin becomes less compact, and the DNA is accessible for transcription DNA Methylation DNA methylation, the addition of methyl groups to certain bases in DNA, is associated with reduced transcription in some species DNA methylation can cause long-term inactivation of genes in cellular differentiation In genomic imprinting, methylation regulates expression of either the maternal or paternal alleles of certain genes at the start of development
Page 1 and 2: The Flow of Genetic Information Th
Page 3 and 4: TRANSCRIPTION DNA mRNA (a) Bacteria
Page 5 and 6: The Genetic Code How are the instr
Page 7 and 8: Cracking the Code All 64 codons we
Page 9 and 10: Molecular Components of Transcripti
Page 11 and 12: RNA Polymerase Binding and Initiati
Page 13 and 14: Eukaryotic cells modify RNA after t
Page 15 and 16: 5′ Exon Intron Exon Intron Pre-mR
Page 17 and 18: The Functional and Evolutionary Imp
Page 19 and 20: Polypeptide Trp Phe Ribosome Amino
Page 21 and 22: Amino acid P P P ATP Adenosine Amin
Page 23 and 24: Building a Polypeptide The three s
Page 25 and 26: The elongation cycle of translation
Page 27 and 28: Growing polypeptides Completed poly
Page 29 and 30: Polypeptide synthesis always begins
Page 31 and 32: Type of RNA Small nucleolar RNA (sn
Page 33 and 34: RNA polymerase RNA polymerase Polyr
Page 35 and 36: Individual bacteria respond to envi
Page 37 and 38: Eukaryotic gene expression can be r
Page 39: CYTOPLASM mRNA in cytoplasm Degrada
Page 43 and 44: Epigenetic Inheritance Although th
Page 45 and 46: The Roles of Transcription Factors
Page 47 and 48: Mechanisms of Post-Transcriptional
Page 49 and 50: Initiation of Translation The init
Page 51 and 52: Noncoding RNAs play multiple roles
Page 53: Chromatin Remodeling and Silencing

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