III. DNA, RNA, and Chromosome Structure

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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure
Avery, McCarty, and MacLeod
Chase and Hershey
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure
Watson and Crick
Pauling
Wilkins
Franklin
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure
DNA is the genetic material in all forms of life
(eubacteria, archaea, protists, plants, fungi,
and animals). Those quasi-living viruses vary
in their genetic material. Some have
double-stranded DNA (ds-DNA) like living
systems, while others have ss-DNA, ss-RNA, and
ds-RNA. RNA performs a wide array of functions
in living systems. Many of these functions have
only been discovered in the last few years.
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides three parts - pentose sugar
(ribose in RNA, deoxyribose in DNA)
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides three parts - pentose sugar
(ribose in RNA, deoxyribose in DNA) -
nitrogenous base (A, C, G, U in RNA A, C, G, T
in DNA)
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides three parts - pentose
sugar - nitrogenous base
Nitrogenous base binds to the 1 carbon
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides three parts - pentose
sugar - nitrogenous base - phosphate group
PO4 binds to the 5 carbon
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides three parts - pentose
sugar - nitrogenous base - phosphate group
Diphosphates and triphosphates occur, also. In
fact, here is ATP, the energy currency of the
cell. The nucleotides exist as free
triphosphates before they are linked into a
nucleic acid chain.
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides 2. polymerization occurs by
dehydration synthesis
Between the PO4 (which always has free H ions
binding and unbinding) of the free nucleotide and
the OH group on the 3 carbon of the last sugar
in the chain.
OH
H2O
OH
Energy released by cleaving the diphosphate group
can be used to power the dehydration synthesis
reaction
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides 2. polymerization occurs by
dehydration synthesis
Polymerization results in a polymer of DNA (or
RNA). This single polymer is a single-stranded
helix It has a polarity or directionality
it has different ends there is a reactive
phosphate at one end (5) and a reactive OH at
the other (3). So, the helix has a 5-3
polarity.
5
3
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides 2. polymerization occurs by
dehydration synthesis 3. most DNA exists as a
double-helix (ds-DNA) (although some viruses
have genetic material that is signle-stranded DNA
(ss-DNA))
a. The nitrogenous bases on the two helices are
complementary to one another, and form weak
hydrogen bonds between the helices.
A purine (A or G) always binds with a pyrimidine
(T or C) In fact, A with T (2 h-bonds) And G
with C (3 h-bonds)
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides 2. polymerization occurs by
dehydration synthesis 3. most DNA exists as a
double-helix (ds-DNA) a. bases are
complementary b. the strands are
anti-parallel they are aligned with opposite
polarity
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(No Transcript)
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides 2. polymerization occurs by
dehydration synthesis 3. most DNA exists as a
double-helix (ds-DNA) 4. RNA performs a wide
variety of functions in living cells a.
m-RNA is a copy of a gene, read by the ribosome
to make a protein
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides 2. polymerization occurs by
dehydration synthesis 3. most DNA exists as a
double-helix (ds-DNA) 4. RNA performs a wide
variety of functions in living cells a.
m-RNA is a copy of a gene, read by the ribosome
to make a protein b. R-RNA is made the same
way, is IN the Ribosome, and reads the
m-RNA
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides 2. polymerization occurs by
dehydration synthesis 3. most DNA exists as a
double-helix (ds-DNA) 4. RNA performs a wide
variety of functions in living cells a.
m-RNA is a copy of a gene, read by the ribosome
to make a protein b. r-RNA is made the same
way, is IN the Ribosome, and reads the m-RNA
c. t-RNA is made the same way, and brings
amino acids to the ribosome
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides 2. polymerization occurs by
dehydration synthesis 3. most DNA exists as a
double-helix (ds-DNA) 4. RNA performs a wide
variety of functions in living cells a.
m-RNA is a copy of a gene, read by the ribosome
to make a protein b. r-RNA is made the same
way, is IN the Ribosome, and reads the m-RNA
c. t-RNA is made the same way, and brings
amino acids to the ribosome d. mi-RNA
(micro-RNA) and si-RNA (small interfering RNA)
bind to m-RNA and splice it
inhibiting the synthesis of its protein. This is
a regulatory function.
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure 1. monomers are
nucleotides 2. polymerization occurs by
dehydration synthesis 3. most DNA exists as a
double-helix (ds-DNA) 4. RNA performs a wide
variety of functions in living cells a.
m-RNA is a copy of a gene, read by the ribosome
to make a protein b. r-RNA is made the same
way, is IN the Ribosome, and reads the m-RNA
c. t-RNA is made the same way, and brings
amino acids to the ribosome d. mi-RNA
(micro-RNA) and si-RNA (small interfering RNA)
bind to m-RNA and splice it
inhibiting the synthesis of its protein. This is
a regulatory function. e. Sn-RNA (small
nuclear RNA) are short sequences that process
initial m-RNA products, and also
regulate the production of r-RNA, maintain
telomeres, and regulate the action of
transcription factors. Regulatory functions.
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure B. Chromosome Structure 1.
Prokaryotes - usually one circular chromosome,
tethered to the membrane, with some associated,
non-histone proteins.
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure B. Chromosome Structure 1.
Prokaryotes 2. Eukaryotes usually many linear
chromosomes, highly condensed with histone
proteins into several levels of structure.
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure B. Chromosome Structure 1.
Prokaryotes 2. Eukaryotes usually many linear
chromosomes, highly condensed with histone
proteins into several levels of structure.
a. Level 1 ds-DNA is wrapped around histone
proteins, creating the beads on a string level
of organization.
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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure B. Chromosome Structure 1.
Prokaryotes 2. Eukaryotes usually many linear
chromosomes, highly condensed with histone
proteins into several levels of structure.

• Level 1 ds-DNA is wrapped around histone
  proteins, creating the beads on a string level
  of organization.

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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure B. Chromosome Structure 1.
Prokaryotes 2. Eukaryotes usually many linear
chromosomes, highly condensed with histone
proteins into several levels of structure.

1. Level 1 ds-DNA is wrapped around histone
   proteins, creating the beads on a string level
   of organization.
2. Level 2 string is coiled, 6 nucleosomes/turn
   (solenoid)

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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure B. Chromosome Structure 1.
Prokaryotes 2. Eukaryotes usually many linear
chromosomes, highly condensed with histone
proteins into several levels of structure.

1. Level 1 ds-DNA is wrapped around histone
   proteins, creating the beads on a string level
   of organization.
2. Level 2 string is coiled, 6 nucleosomes/turn
   (solenoid)
3. Level 3 the coil is supercoiled

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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure B. Chromosome Structure 1.
Prokaryotes 2. Eukaryotes usually many linear
chromosomes, highly condensed with histone
proteins into several levels of structure.

1. Level 1 ds-DNA is wrapped around histone
   proteins, creating the beads on a string level
   of organization.
2. Level 2 string is coiled, 6 nucleosomes/turn
   (solenoid)
3. Level 3 the coil is supercoiled
4. Level 4 the supercoil is folded into a fully
   condensed metaphase chromosome

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III. DNA, RNA, and Chromosome Structure A. DNA
and RNA Structure B. Chromosome Structure 1.
Prokaryotes 2. Eukaryotes usually many linear
chromosomes, highly condensed with histone
proteins into several levels of structure.
To read a gene, the chromosome must be diffuse
(uncondensed) in that region. Even when
condensed, these euchromatic coding regions are
less condensed and more lightly staining than
non-coding regions. DNA that has few genes can
remain condensed and closed (heterochromatic),
and appears as dark bands on condensed
chromosomes.
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  Study Questions 1) Diagram the parts of an
RNA nucleotide. 2)  Show how two nucleotides are
linked together by dehydration synthesis
reactions. 3) Why does the purine - pyrimidine
structure relate to the complementary nature of
double-stranded DNA? 4)  Draw a DNA double
helix, showing three base pairs and the
antiparallel nature of the helices. 5) Describe
the higher levels of eukaryotic chromosome
structure, including the terms nucleosome and
solenoid. 6) What are two differences between
euchromatin and hetochromatin?