Structure and Organization of DNA

Question 1

Found in conditions of LOW humidity and HIGH salt concentration

Answer 1

A DNA

right handed double helix

Question 2

MC FORM

Found in conditions of HIGH humidity and LOW salt conditions

highly flexible

Answer 2

B-DNA

Right handed double helix

Question 3

Phosphodiester backbone assume a zigzag form

Seen in the 5’ end of chromosomes

Answer 3

Z DNA

Left handed DNA

Question 4

Determine the MELTING point of DNA

Answer 4

check the G-C content

INC G-C content
INC melting point

Question 5

The most abundant chromatin protein

Answer 5

HISTONES

Question 6

First level of organization of DNA

2 nm

Answer 6

DNA double helix

Question 7

Consists of nucleosomes + linker DNA

beads on a string appearance

Answer 7

10 nm chromatin fibril

Question 8

Group of nucleosomes

Answer 8

30 nm DNA chromatin fibril (solenoid)

Question 9

Promotes packing of DNA into compact structure

Answer 9

Supercoiled structure

Question 10

Enzymes that can RELAX or INSERT supercoils

RELIEVE TORSIONAL STRAINS in DNA

Answer 10

Topoisomerase

Question 11

Make transient SINGLE STRANDED BREAK in an negatively supercoiled DNA double helix

DISRUPTS PHOSPHODIESTER bond

Answer 11

TOPOISOMERASE 1

does NOT need ATP

Question 12

Dimeric enzyme that bind to DOUBLE STRANDED DNA, make breaks in BOTH STRANDS of DNA

Answer 12

TOPOISOMERASE II

ATP is needed

Question 13

Chromatin is LESS DENSELY PACKED and STAINS LESS DENSELY

Transcriptionally ACTIVE

Answer 13

EUCHROMATIN

Question 14

Chromatin is DENSELY PACKED and STAINS DENSELY

Transcriptionally INACTIVE

Answer 14

HETEROCHROMATIN

Question 15

Always CONDENSED

Essentially INACTIVE

Answer 15

CONSTITUTIVE HETEROCHROMATIN

• centromere
• chromosomal ends of telomere

Question 16

At times condensed but at other times uncondensed and actively transcribed

Answer 16

one of the x chromosome in mammalian female

heterochromatic x chromosome decondenses during gametogenesis

Question 17

Central Dogma of Molecular Biology

Answer 17

DNA replication (DNA –> DNA)
Transcription ( DNA –> RNA)
Translation (RNA –> protein)

Question 18

The COMPLETE set of genes of an organism

Answer 18

GENOME

Question 19

The complete set of RNA transcripts produced by the genome of an organism

Answer 19

TRANSCRIPTOME

Question 20

The COMPLETE set of RNA transcripts produced by the genome of an organism

Answer 20

TRANSCRIPTOME

Question 21

The complete COMPLEMENT of proteins of an organism

Answer 21

PROTEOME

Question 22

DNA STRUCTURE

Answer 22

All nucleotides are involved in linkage
Antiparallel
Bases are perpendicular to DNA
Attached by hydrogen bond

Question 23

2 strands of DNA are held together by

Answer 23

Hydrogen Bond

Question 24

At physiological pH the DNA molecules are

Answer 24

NEGATIVELY CHARGED - d.t. phosphate group

Question 25

Triplex DNA is d.t.

Answer 25

Hoogsteen pairing

Question 26

Which model of DNA was discovered by Watson and Crick?

Answer 26

B DNA

Question 27

Random inactivation of X chromosome

Answer 27

Lyonization

Question 28

Changes the expression of a DNA segment without changing the sequence

aging, carcinogenesis, genomic imprinting, transposable element repression and inactivation of the X chromosome

Answer 28

DNA METHYLATION

Question 29

Reversible transcriptional supression

Answer 29

Histone Methylation

Question 30

Removal of histone’ s (+) charge –> relaxed DNA coiling –> INCREASE TRANSCRIPTION

Answer 30

HISTONE ACETYLATION

Question 31

Removal of acetyl groups –> tightened DNA coiling –> DECREASE TRANSCRIPTION

Answer 31

HISTONE DEACETYLATION