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Clase anterior:- eg as e arga- Datos de difraccin de rayos X- Estructura de la doble hlice

- Componentes: pentosa, fosfato y base nitrogenada- Tipos de bases nitrogenadas-- Estructuras alternativas de la doble hlice

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Nucleic acids can adopt different conformations.

* B-DNA is found at low salt concentrations. It is believed to be the native conformationoccurring in chromatin.right-handed helix; sugar pucker: C2'-endo; number of nucleotides per pitch: 10; h:

. .

* A-DNA is found in solutions with higher salt concentrations or with alcohol addedright-handed helix; sugarpucker: C3'-endo; number of nucleotides per pitch: 11; h:

. . .

* Z-DNA occurs for alternating poly(dG-dC) sequences in solutions with high salt

concentrations or alcohol.- - '- -

conformation, sugar pucker: C2' endo; number of nucleotides per pitch: 6x2; h:3.7x2 ; t= -30x2

* - '-form).

http://www.imb-jena.de/IMAGE_DNA_MODELS.html

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dA dG

T dC

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dA dG

T dC

anti-conformation syn-conformation

In order for base-pairing

QuickTime and aTIFF (Uncompressed) decompressor

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to occur in a nucleicacid, the anti-conformation is

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dA dG

T dC

anti-conformation syn-conformation

In order for base-pairing

QuickTime and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime and aTIFF (Uncompressed) decompressor

are needed to see this picture.

to occur in a nucleicacid, the anti-conformation is

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In molecular biology, a wobblebase pair is a non-Watson-Crick base pairing between two

(codon-anticodon). The fourmain wobble base pairs areguanine-uracil, inosine-uracil,

- , -cytosine (G-U, I-U, I-A and I-C).The thermodynamic stability of

a wobble base pair is

Crick base pair.

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A tri le-stranded DNA is a structure of DNA in which three oli onucleotides wind

DNA triple hlice

around each other and form a triple helix. In this structure, one strand binds to aB-form DNA double helix through Hoogsteen or reversed Hoogsteen hydrogenbonds.

The triplexes also form most readily within long sequences containing onlypyrimidines or only purines in a given strand. Some triplex DNAs contain two

pyrimidine strand.

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exotic DNA structure, known as-,important during DNArecombination

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Secuencia palindrmica o palndrome

A palindrome is a word, phrase, or sentencethat is spelled identically read either forward or backward;

.

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DNA Replication

DNA replication is a semi-conservative process.One strand serves as the template for the secondstrand. DNA replication is initiated at a region ona chromosome called an origin of replication. Anenzyme called DNA Helicase binds to the origin

and unwinds the DNA in both directions from theorigin.

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Otro tipo de cido nucleico:

Main types of RNAs

RNA

mRNAs messenger RNAs, code for proteins.

tRNAs

,protein synthesis.

transfer RNAs, carry specific amino acids to the elongating

snRNAs

peptide chain during translation.

small nuclear RNAs, function in a variety of nuclear processes,- .

Ribozimas

ssDNA

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Funciones de los nucletidos

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Estructura del cAMP

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Bromodeoxyuridine (5-bromo-2-deoxyuridine, BrdU) is a synthetic nucleoside that is ananalogue of thymidine. BrdU is commonly used in the detection of proliferating cells inliving tissues.

BrdU can be incorporated into the newly synthesized DNA of replicating cells (during the Sphase of the cell cycle), substituting for thymidine during DNA replication.

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QuickTime and aTIFF (Uncompressed) decompressor

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QuickTime and aTIFF (Uncompressed) decompressorare needed to see this picture.

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QuickTime and aTIFF (Uncompressed) decompressorare needed to see this picture.

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are needed to see this picture.

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Aciclovir- a guanine derivative, DNA polymerase inhibitor and antiviral

TIFF (Uncompressed) decompressor

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Nucletidos modificados

Pseudouridine () was discovered tobe the most abundantposttranscriptionally modifiedQuickTime and a

TIFF Uncom ressed decom ressor

nucleotide in cellular RNAs in the

1950s

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DNA metiltransferasas

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Nucletidos modificados

Pseudouridine () was discovered tobe the most abundantposttranscriptionally modifiedQuickTime and a

TIFF Uncom ressed decom ressor

nucleotide in cellular RNAs in the

1950s

are needed to see this picture.

X

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are needed to see this pict

desaminacin espontnea de citosina,

Xuracilo

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Nucletidos modificados

Pseudouridine () was discovered tobe the most abundantposttranscriptionally modifiedQuickTime and a

TIFF Uncom ressed decom ressor

nucleotide in cellular RNAs in the

1950s

are needed to see this picture.

desaminacin espontnea de 5-metil

(una mutacin tipo transicin)

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Lack an -OH group atthe 3-carbon osition

Cannot add another

nucleoside at that

Prevent further DNAsynthesis

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Reversible denaturation and annealing of DNA

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ec o pocr m co percr m co

Bases in DNA absorb light at 260 nm.

The close proximity of the bases in double-stranded DNA quenches some of the

absorbance- hypochromic shift.

When the two strands separate, this quenching disappears and the absorbancerises 30-40% hyperchromic shift.

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Denaturation of DNA Causes Hyperchromism

0nm)Tm: temperatura a la cual

el 50% del DNA escadena doble

istryp.73

91.3

ce(26

Depende de factores como:

Com osicin nucleotdica

tal

ofBiochem

1.2

so

rban

Tm

Entorno (fuerza inica, pH,)Largo (complejidad) de las

cadenas a hibridar

99)Fundamen

1.1tiveab

Voetetal(

19

Rela

Adap

tedfro.

Temperature (C)

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G+C Content Is Proportional to Tm

1.40nm)

Pneumococcus

(38%) G+C E. coli (52%)

ce(26

S. Marcescens

(58%))p.3

72

1.2so

rban

iochemistry(2

tiveab

M. Phleiham(

1999)Bi

70 80 90 1001.0R

ela

Garrett&G

ri

Temperature (C)

Adap

tedfro

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3 X 1 05

molculas de ene co ia nica corres onden a:

Tamao genoma (pb)1 g DNA humano ~3 X 109

~ 7.1 ng DNA E. coli ~ 4 X 106

0.3 pg pBSSK ~2.9 X 103

C ti N t li Ph h t d El t T

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Cation Neutralizes Phosphate and Elevates Tm

0.01 M phosphate0.001 M EDTA 35

)

40+C(

200.15 M NaCl

0

.

5 3

60 70 80 90 100 110

Tm (C) Adapted from Garrett & Grisham (1999) Biochemistry (2e) p.372

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Sntesis qumica de oligonucletidos

1.DesproteccinConsiste en eliminar medianteun tratamiento ligeramentecido, al grupo DimetoxitritiloDMT . Este ru o rote e al

Hidroxilo 5' terminal de labase (nucletido)correspondiente.

2.AcoplamientoUna vez libre el grupohidroxilo, se adiciona elsiguiente nucletido, en formade -cianoetilfosforamidito,correspondiente a la

sequencia deseada..Concludo el paso deacoplamiento, se bloqueantodos los hidroxilos que noreaccionaron (menor al 2%del total) con la nueva base,

-cianoethylphosphoramidite

esto mediante una reaccinde acetilacin.

4.OxidacinFinalmente, el grupo fosfitointernucleotdico se oxida a ungrupo os a o es a e.

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TAREA:

Qu es una topoisomerasa?

Tipos de topoisomerasa y cul son sus funciones?