chapter 9: molecular structure of dna and rna

information, entire, transmission, parent, offspring, replication, copied, variation, changes

Introduction

• to a large extent, out knowledge of genetics comes from out knowledge of the molecular structure of DNA and RNA

• genetic material must meet several criteria:

  • …… : it must contain the information necessary to make an …. organism

  • …. : it must be passed from … to …

  • …. : it must be ….

    • in order to be passed from parent to offspring

  • …. : it must be capable of ….

    • to account for the known phenotypic variation in each species

large macromolecules, repeating, nucleic, linear strand, rna, dna, 2, double helix, folding, bending, proteins, chromosomes, living

DNA and RNA are … …. with several levels of complexity

1. nucleotides are the …. unit of …. acids, and are linked to form a … … of … or ….

2. … strands interact to form a …. …

3. the 3-D structure of DNA results from … and … of the double helix

   1. interaction of dna with … produces … within … cells

phosphate, pentose sugar, dexoyribose, ribose, nitrogenous

Nucleotide structure:

• the nucleotide is the repeating structural unit of DNA and RNA

  • a …. group

  • a … … (… vs …)

  • a ….. base

nucleoside, adenosine, nucleotide, adenosine monophosphate

Nucleosides vs Nucleotides

• base + sugar → ….

  • example

    • adenine + ribose = ….

    • adenine + deoxyribose = deoxyadenosine

• base + sugar + phosphate(s) → ….

  • example

    • … … (AMP)

condensation, 3, OH, 5, phosphate, water

Nucleotides polymerize via phosphodiester bonds

• these are …. reactions between the …’ …. and …’ … group: a … is produced

polymerization, nucleic, 3, carbon, ribonucleotide, 5, carbon, ribonucleotide, nucleotides, unlinked 3

Strand directionality:

• the …. reaction provides directionality to the … acids

• phosphodiester linkage connects the …’ …. of one … and the …’ … of another ….

• 3’ end of nucleic acid:

  • new … are added to the … ….’ carbon

watson, crick

Discovery of the double helix:

• in 1953, james …. and francis … elucidated the double helical structure of DNA

covalently, phosphodiester, 5, 3, directionality, sugar, same, phosphates, sugar, bases, rungs

Nucleic acid directionality:

• nucleotides are … linked together by … bonds

  • a phosphate connects the ….’ carbon of one nucleotide to the ..’ carbon of another

• therefore, the strand has …

  • 5’ to 3’

  • in a strand, all …. molecules are oriented in the … direction

• the … and .. molecules form the backbone of the nucleic acid strand

  • the … project from the backbone and make the ….

pauling, secondary, alpha, ball, stick

in the early 1950s, ….. proposed that regions of protein can fold into a …. structure called an …. helix

to elucidate this structure, he built … and … models

franklin, wilkins, x ray diffraction, dna, wet fibers, structure

• ….. worked in the same laboratory as maurice ….

• made major advances in … … … techniques with ….

  • techniques used to study … … of DNA

• the diffraction pattern is interpreted (using mathematical theory)

  • can ultimately provide information concerning the … of the molecule

helical, more, one, 10 base, complete turn

Rosalind Franklin:

• the diffraction pattern she obtained suggested several structural features of DNA:

  • ….

  • …. than .. strand

  • … … pairs per … …

scatter, distances, 0.34, 3.4, 2

Maurice Wilkins and Rosalind Franklin bombarded DNA with X-rays (x-ray crystallography) to analyze the … pattern - were able to calculate the …. between groups of atoms

3 repeating units:

one every … nm

one every … nm

diameter of … nm

nucleotides, sugar, phosphate, phosphodiester, equal, equal, equal

What was known before Watson and Crick’s discovery?

• structure of ..

• dna has a …. - … backbone

• dna polymerized through … bonds

• number of purines … number of pyrimidines

• A’s … T’s

• C’s … G’s

ball, stick, outside, toward, H, identical, opposite, incorrect

Enter James Watson and Francis Crick:

• built … and … models with the:

  • sugar-phosphate backbone on the …

  • bases projecting … each other

• they first considered a structure in which bases form … bonds with … bases in the …. strand

  • ex. A to A, T to T, C to C, and G to G

• model building revealed that this was ….

similar

Watson and Crick:

• they then realized that the hydrogen bonding of A to T was structurally … to that of C to G

  • so they built ball and stick models with AT and CG interactions between the 2 DNA strands

    • these were consistent with all known data about DNA structure

twisted, common, 10, 3.4, turn, antiparallel, asymmetrical grooves, outside, major, minor, proteins, bases, right, away, clockwise

Structural Features of DNA

• 2 strands are …. together around a … axis

• there are … bases (… nm) per complete … of the helix

• the 2 strands are ..

  • one runs in the 5’ to 3’ direction and the other 3’ to 5’

• there are 2 … …. on the …. of the helix

  • …. groove and … groove

  • certain … can bind within these grooves

    • they can thus interact with a particular sequence of …

• the helix is … handed

  • as it spirals … from you, the helix turns in a …. direction

phosphate, sugar, negative, concealed, interior, antiparallel

DNA structure

• outside is the ….. / ….. backbone

  • … charge to dna

• bases are … in the … of the structure

• strand are …

hundred, thousand, one, template

RNA structure

• the primary structure of an RNA strand is much like that of a DNA strand

• RNA strands are typically several … to several .. nucleotides in length

• in RNA synthesis, only … of the 2 strands of DNA is used as a …

uracil, ribose, 2

RNA uses … as a base

rna uses … with ..’ OH

hydrogen, away, double, hair pins

• complementary regions

  • held together by … bonds

• noncomplementary regions

  • have bases projecting …. from … stranded regions

• stem loops are also called …. ….

tertiary, pairing, stacking within, ions, small molecules, large proteins, single, double, fold, interact

• many factors contribute to the … structure of RNA

  • for example, base …. and base … … the RNA itself

  • interactions with …., .. …, and … …

  • molecule contains …. and … stranded regions

  • these spontaneously …. and … to produce this 3-D structure