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Dry-bulb temperature: The temperature of the air, as measured by a thermometer
Humidity ratio: The amount of water in the air relative to the amount of dry air
Wet-bulb temperature: Another temperature measurement of the air
Dew-point temperature: The temperature at which water will start to condense
Enthalpy: A measurement of heat energy in the air
Specific volume: A measurement of air density
How to use a psychrometric chart
Locate the point where your known measurements intersect on the chart
Use a ruler to follow the lines extending from that point to the various scales on the chart
Read the other measurements from the scales
Applications

1. 13.1 RNA Consisting of a Single Strand of
Ribonucleotides Participates in a Variety of
Cellular Functions

2. •Primary structure
•Secondary structure
The Structure of RNA

5. Classes of RNA
•Ribosomal RNA – rRNA
•Messenger RNA – mRNA
•Transfer RNA – tRNA
•Small nuclear RNAs – snRNAs
•Small nuclear ribonucleoproteins – snRNPs
•Small nuclear RNAs – snoRNAs

6. Classes of RNA
•Small cytoplasmic RNAs – scRNAs
•MicroRNAs – miRNAs
•Small interfering RNAs – siRNAs
•Piwi-interacting RNAs – PiRNAs

8. 13.2 Transcription Is the Synthesis of an
RNA Molecule from a DNA Template
RNA polymerase enzyme reads template and
synthesizes complementary RNA sequence

9. The Template
The transcribed strand: template strand
Transcription will produce an RNA molecule
that resembles the opposite strand or the
nontemplate strand
RNA polymerase moves along template strand
in 3’-5’ direction and produces new RNA in
5’-3’ much as in DNA replication.

11. Usually only one strand will serve as template in a
region of DNA, however, throughout the DNA
molecule each strand can be used as template

13. The Template
•The transcription unit
•Promoter-initiates transcription
•RNA coding sequence-contains sequence
that will be reflected in RNA molecule
•Terminator-halts transcription and releases
RNA molecule

15. Initiation
•The substrate for transcription:
•Ribonucleoside triphosphates – rNTPs added
to the 3′ end of the RNA molecule
•rGTP, rCTP, rATP, and rUTP

16. Initiation
•The transcription apparatus:
•Bacterial RNA polymerase: five subunits made
up of the core enzyme:
•Two copies of α
•Single copy of β
•Single copy of β′
•A stabilize enzyme: ω
•The sigma  factor: binding to the promoter
when transcription starts

18. Initiation
•The substrate for transcription:
•Ribonucleoside triphosphates – rNTPs added
to the 3′ end of the RNA molecule
•The transcription apparatus:
•Eukaryotic RNA polymerases

20. Initiation
•Bacterial promoters:
•Consensus sequences: sequences that
possess considerable similarity
•−10 consensus: 10 bp upstream of the start
site
•Pribnow box:
•5′ TATAAT 3′
•3′ ATATTA 5′
•−35 consensus sequence: TTGACA

22. Concept Check 2
What binds to the −10 consensus sequence found
in most bacterial promoters?
a.The holoenzyme (core enzyme + sigma factor)
b.The sigma factor alone
c.The core enzyme alone
d.mRNA

23. Concept Check 2
What binds to the −10 consensus sequence found
in most bacterial promoters?
a.The holoenzyme (core enzyme + sigma factor)
b.The sigma factor alone
c.The core enzyme alone
d.mRNA

24. Initiation
•Initial RNA synthesis: No primer is required.
•The location of the consensus sequence
determines the position of the start site.

25. Elongation
•RNA elongation is carried out by the action of
RNA polymerase.

26. Termination
•Rho-independent termination: hairpin structure
formed by inverted repeats, followed by a string
of uracils
•Rho-dependent termination: a hairpin slows
down polymerase allowing a trailing protein
called rho to catch up and dislodge the
polymerase from the template

29. 13.4 The Process of Eukaryotic Transcription Is
Similar to Bacterial Transcription but Has Some
Important Differences

30. Transcription and Nucleosome Structure
– Chromatin modification before transcription
•Promoters:
•Basal transcription apparatus
•Transcriptional activator proteins
•RNA polymerase II – mRNA synthesis
•Core promoter TATA box TATAAAA, −25 to
−30 bp, binded by transcription factors

31. Transcription and Nucleosome Structure
– Chromatin modification before transcription
•Promoters:
•Regulatory promoter
•A variety of different consensus sequences
may be found in the regulatory promoters.
•Main difference between prokaryotes and
eukaryotes is in assembly of complex
structures at promoter in eukaryotes

33. Transcription and Nucleosome Structure
– Chromatin modification before transcription
•Enhancers: distant regions of DNA that
increase transcription levels
•Bound by initiation complex proteins and loop
around to interact with promoter region
•Polymerase I and polymerase III promoters
•Distinct from those of polymerase II
•May sometimes be downstream of transcription
start site

34. Initiation
•RNA polymerase II + transcription factors
•TATA binding protein

36. Elongation
Much the same as in prokaryotes

38. Termination
•RNA polymerase I-terminated by protein that
binds DNA downstream of termination sequence
•RNA polymerase II-terminated by complex
mechanism involving RNA cleavage and Rat1
protein
•RNA polymerase III-terminates after long poly-U
transcript.

40. Concept Check 3
What is the difference between the core promoter
and the regulatory promoter?
a.Only the core promoter has consensus
sequences.
b.The regulatory promoter is farther upstream from
the gene.
c.Transcription factors bind to the core promoter;
transcriptional activator proteins bind to the
regulatory promoters.
d.Both b and c above

41. Concept Check 3
What is the difference between the core promoter
and the regulatory promoter?
a.Only the core promoter has consensus
sequences.
b.The regulatory promoter is farther upstream from
the gene.
c.Transcription factors bind to the core promoter;
transcriptional activator proteins bind to the
regulatory promoters.
d.Both b and c above

42. 13.5 Transcription in Archaea Is More Similar to
Transcription in Eukaryotes than to
Transcription in Eubacteria
•This suggests a closer relationship between
archaea and eukaryotes.