Nucleic Acid Structure

Question 1

Posttranslational Histone Modifications

Answer 1

+Reversible
+Influence chromatin structure and function
+Govern gene activity (transcription)

Question 2

Acetylation

Answer 2

Lysine E-amino group

Question 3

Methylation

Answer 3

Lysine E-amino group

Question 4

O-Phosphorylation

Answer 4

Serine, Threonine

Question 5

N-Phosphorylation

Answer 5

Histidine, Lysine

Question 6

Nucleosome

Answer 6

A structural unit of a eukaryotic chromosome, consisting of a length of DNA coiled around a core of histones

Question 7

How many times does DNA wrap around a nucleosome?

Answer 7

Two times

Question 8

Which histone is not a part of nucleosome core?

Answer 8

H1

Question 9

Histone octamer

Answer 9

The 8 protein complex found at the center of a nucleosome core particle.

Question 10

Which histones make up the histone octamer complex?

Answer 10

+Two H3 and H4

+Two H2A-H2B dimers

Question 11

What modulates transcription?

Answer 11

DNA packing

Question 12

During interphase what is the percent of DNA in heterochromatin?

Answer 12

10% (transcriptionally inactive)

Question 13

During interphase what is the percent of DNA in euchromatin?

Answer 13

90% (10% in open state, 90% in intermediate packed state)

Question 14

How is DNA degraded?

Answer 14

By breaking phosphodiester bonds

Question 15

Enzymes for degradation

Answer 15

DNases
RNases
Exonucleases
Endonucleases

Question 16

Non-enzymatic degradation

Answer 16

Very high heat (>95C)

Question 17

How is DNA denatured?

Answer 17

By breaking H bonds

Question 18

Enzymes for denaturing

Answer 18

Helicases

Question 19

Non-enzymatic denaturation

Answer 19

High heat (

Question 20

Hyperchromicity

Answer 20

The increase of absorbance of a material; occurs when the DNA duplex is denatured; ssDNA absorbs ~40% more than dsDNA

Question 21

Hypochromicity

Answer 21

A decrease of absorbance of a material; dsDNA absorbs ~40% less than free nucleotides

Question 22

DNAs maximal absorbency

Answer 22

A260

Question 23

Melting temperature midpoint (Tm)

Answer 23

Temperature at midpoint of denaturation reaction

Question 24

Factors affecting Tm

Answer 24

+ G+C content
+ Ionic strength
+ Presence of chaotropic agents

Question 25

SSC Buffer

Answer 25

Standard Sodium Citrate

Question 26

Annealing

Answer 26

Forming H-bonds between two ssDNA to yield dsDNA ; depends of complementarity between ssDNA1 and ssDNA2

Question 27

Renaturation

Answer 27

Annealing of ssDNA from one source to reform dsDNA

Question 28

Hybridization

Answer 28

Annealing of ssDNA from 2 sources to form hybrid dsDNA

Question 29

Similarity

Answer 29

Proportion of bases identical in sequence

Question 30

Complementarity

Answer 30

Portion of bases in 2 ssDNA complementary to each other

Question 31

Solution hybridization method 1

Answer 31

Determine A260 (hyperchromicity)

Question 32

Solution hybridization method 2

Answer 32

Hydroxyapatite chromatography

Question 33

ssDNA elutes with ___ Pi buffer

Answer 33

low

Question 34

dsDNA elutes with ___ Pi buffer

Answer 34

high

Question 35

Filter hybridization

Answer 35

Establishes whether a solution of denatured DNA (or RNA) contains sequences complementary to the strands immobilized on the filter

Question 36

Factors affecting reassociation kinetics

Answer 36

+ Temperature (Tm=25) + Monovalent cations block reassociation + High temp weakens secondary structure + Time and concentration to ensure collisions + Size and length of DNA chain (usually shear DNA to 300 bp)

Question 37

Eukaryotes exhibit 3 components (in reassociation kinetics)

Answer 37

+ Fast + Intermediate + Slow

Question 38

Slow component repetition

Answer 38

Single copy

Question 39

Fast component repetition

Answer 39

Many copies (500,00 freq)

Question 40

Intermediate component repetition

Answer 40

Some copies (350 freq)

Question 41

C0t1/2 =

Answer 41

Fraction of genome X C0

Question 42

Complexity of unknown =

Answer 42

C0t1/2 of unknown X Complexity of standard /// C0t1/2 of standard

Question 43

Chemical complexity (genome size) =

Answer 43

Nucleic acid /// Nucleus

Question 44

Stringency

Answer 44

Control amount of mismatch permitted in reaction

Question 45

F (repetition frequency) =

Answer 45

Chemical complexity /// kinetic complexity