Ch24

DNA is composed of ____ nucleotides

A, G, C, and T

DNA forms a ____ of two separate strands with complementary sequences (____).

double helix; antiparallel

During replication, the two strands unwind, each serving as a template for a new daughter double helix ____

semiconservative replication

DNA/RNA is a long polymer of nucleotides: The _____ is the information content of the nucleic acid.

sequence of the bases

What is the size of the human genome?

3 billion base pairs

Nucleotides are linked by phosphodiester bonds

- begins with a free 5' OH or 5' OH attached ot a phosphoryl group

- directionality: 5' to 3'

Nucleic acid chains are presented by abbreviations such as ___, ___ or more simply ____.

pAPGpCpT, pAGCT, AGCT

Nucleic acid chians have ____ in that the two ends are different. One end has a ___ or ____ and the other has a free ____ attached to the sugar.

directionality; 5' OH; Phosphate/PP/PPP-O; 3' OH

Nucleic acid chains ar ewritten in the ____ direction

5' to 3' direction

DNA double helix: DNA molecules consist of two ____ chians both in 5' to 3' direction - intertwined to form a ___.

antiparallel; right handed double helix

DNA double helix: The sugar-phosphate backbones are on the ___ of the helix, wheras the bases are __ the helix, forming base paring.

outside; inside

DNA double helix: the Helix is approximately ___ A wide

20

Francis Crick and James Watson predicted the DNA double helix structures and started building the model of DNA based on ____ in ____.

Rosalind Franklin; 1953

X ray diffraction image of DNA: the corss in the center means a ___. The heavy bands at the top and bottom mean the ___. Franklin also suggested that the ____ and the ___.

helical structure; recurring bases; backbone was on the outside; bases were on the inside

Double helix of DNA is stabilized

hydrogen bonds and base stacking force

Hydrogen bond

A=T and G=C

Hydrogen bonds involve the ___ and __ groups

amino carbonyl

Base pairs:

G-C pair is more stable than A-T

Base stacking is what type of interaction

hydrophobic

The two strands of DNA serves as a backup for each otheer

Bc of the base pairing rules, the sequence of one strand determines the sequence of the other strand

The two strands of DNA serves as a backup for each other

the two strands can be separated and complementary sequences synthesized to generate two identicl daughter strands

Who demonstrated that replication is semiconservative.

Meselson and Stahl

DNA consisted of

equal parts of 15N and 14N

Denaturation of DNA

dsDNA to ssDNA

During what, the two strands of DNA must be separated

replication or transcription

in the laboratory, DNA strands can be separated by heating a process called denaturation or melting. The temperature at which half of the DNA molecules are denatured is called the ____.

melting temperature

Upon cooling, the two strands can bind to one nother to reform the double helix, a process called ---?.

reannealing

Why does a higher GC content result in higher Tm?

GC pairs have 3 hydrogen bonds, stronger base stacking, which increases DNA duplex stability

In the cell the most commonly seen form of DNA is called

B form

What is shorter and wider than B form

A form

The A form is also seen in ___ and ___.

RNA; RNA-DNA

The double helix can also form

Z DNA, left-handed and zigzagged

B form DNA has a

major groove and minor groove

Grooves

expose the base to interact with other molecules by forming hydrogen bonds, usually in a sequence-specific manner

The human genome size is

3 billion base pairs

How many chromosomes do humans have?

46 chromosomes

What accounts for some of the compaction of DNA

supercoiling

Further compaction occurs by binding certain proteins to the DNA to form

nucleosomes and chromatin

In prokaryotes the DNA double helix is a circulat molecule that is twisted into a superhelix by the process of

supercoiling

Linear DNA molecules in ___, can also form superhelices when packaged into chromosomes

eukaryotes

What is composed of linear DNA and histone proteins?

chromatin

Histones are fundamental proteins

especially at the tail part

What comprises a core particle

H2A, H2B, H3, H4, and 147

The core particles are joined by 50 bp linker DNA, to which ___ binds

histone H1

Digestion of the linker DNA yields the

nucleosome core particle

The eight histones of the core particle are arranged as an

octamer

DNA wraps around the outside of the octamer in a ___ way

left handed

RNA structure

intramolecular double-stranded structure, stem loop.

Non-Watson-Crick base pairs occurs in RNA such as

GU base pair