chapter 10

Nucleotide

The monomer/building block of nucleic acids.

Deoxyribonucleotide

A nucleotide that makes up DNA, composed of deoxyribose, a phosphate group, and a nitrogenous base.

Deoxyribose

The five-carbon sugar component of a DNA nucleotide.

Nitrogenous base

A nitrogen-containing ring structure responsible for complementary base pairing between nucleic acid strands.

Nucleoside

A molecule composed of a five-carbon sugar and a nitrogenous base (no phosphate group).

Purines

Nitrogenous bases with a double-ring structure; includes adenine (A) and guanine (G).

Pyrimidines

Nitrogenous bases with a single six-carbon ring structure; includes cytosine (C) and thymine (T).

Phosphodiester bond

The covalent bond linking the phosphate group of one nucleotide's 5' carbon to the hydroxyl group of the next nucleotide's 3' carbon.

Sugar-phosphate backbone

The alternating sugar-phosphate structure forming the structural framework of a nucleic acid strand.

Deoxynucleotide triphosphate (dNTP)

The nucleotide form used during DNA polymerization, releasing pyrophosphate as two phosphates are cleaved.

Erwin Chargaff

Austrian biochemist who discovered that the amount of adenine equals thymine, and cytosine equals guanine, in DNA (Chargaff's rules).

Chargaff's rules

The principle that in DNA, A = T and G = C in quantity.

Linus Pauling

American chemist who proposed an incorrect triple-stranded model of DNA structure in 1952.

Rosalind Franklin

British scientist whose X-ray diffraction images (with R.G. Gosling) revealed the double-helix structure of DNA.

James Watson and Francis Crick

Scientists who, in 1953, used Chargaff's rules and Franklin/Wilkins' X-ray diffraction data to propose the DNA double helix model.

Antiparallel

Describes the orientation of the two DNA strands, in which the 3' end of one strand faces the 5' end of the other.

Major groove

The wider gap between the sugar-phosphate backbones of the DNA double helix, a site for protein binding.

Minor groove

The narrower gap between the sugar-phosphate backbones of the DNA double helix, a site for protein binding.

Complementary base pairing (DNA)

Adenine (A) pairs with thymine (T) via 2 hydrogen bonds; cytosine (C) pairs with guanine (G) via 3 hydrogen bonds.

DNA denaturation

The separation of double-stranded DNA into single strands due to heat or chemicals breaking hydrogen bonds.

DNA renaturation (reannealing)

The process by which separated single DNA strands recombine into double-stranded DNA upon cooling or removal of denaturants.

Vertical gene transfer

The transmission of genetic information from a parent cell to daughter cells via DNA replication.

Ribonucleotide

The nucleotide building block of RNA, composed of ribose, a phosphate group, and a nitrogenous base.

Ribose

The five-carbon sugar found in RNA nucleotides (has an OH group at the 2' carbon, unlike deoxyribose).

Uracil

The RNA-specific pyrimidine base that pairs with adenine, used instead of thymine in RNA.

Messenger RNA (mRNA)

The type of RNA that carries genetic information copied from DNA to the ribosome to direct protein synthesis.

Ribosomal RNA (rRNA)

A stable RNA type making up about 60% of the ribosome's mass; ensures proper alignment of mRNA, tRNA, and ribosome, and catalyzes peptide bond formation.

Transfer RNA (tRNA)

A small, stable RNA (70-90 nucleotides) that carries the correct amino acid to the ribosome during protein synthesis.

Peptidyl transferase

The enzymatic activity of rRNA that catalyzes peptide bond formation between amino acids.

Francois Jacob and Jacques Monod

French scientists who in 1961 hypothesized the existence of messenger RNA as an intermediary between DNA and protein.

Thomas Steitz and Peter Moore

Scientists who in 2000 crystallized ribosome structure from Haloarcula marismortui, proving rRNA's catalytic role; Steitz shared the 2009 Nobel Prize in Chemistry for this work.

Intramolecular base pairing

Base pairing that occurs within a single RNA strand (folding back on itself), creating three-dimensional structure.

RNA as hereditary information

RNA serves as the genetic material for many viruses (which lack DNA), such as rhinoviruses, influenza, and Ebola virus (single-stranded) and rotaviruses (double-stranded).

Key differences between DNA and RNA

DNA is typically double-stranded and long-term/stable (deoxyribose, thymine); RNA is typically single-stranded and short-term/less stable (ribose, uracil).