CHAPTER 11

DNA polymerase

An enzyme that bonds DNA nucleotides together into a continuous strand, using a preexisting DNA strand as a template.

DNA ligase

An enzyme that bonds the terminal sugar in one DNA strand to the terminal phosphate in a second DNA strand, creating a single strand with a continuous sugar-phosphate backbone.

DNA helicase

An enzyme that helps unwind the DNA double helix during DNA replication.

DNA replication

The copying of the double-stranded DNA molecule, producing two identical DNA double helices.

base

(1) A substance capable of combining with and neutralizing H+ ions in a solution; a solution with a pH greater than 7; (2) One of the nitrogen-containing, single- or double-ringed structures that distinguishes one nucleotide from another. In DNA, the bases are adenine, guanine, cytosine, and thymine.

sugar-phosphate backbone

A chain of sugars and phosphates in DNA and RNA; the sugar of one nucleotide bonds to the phosphate of the next nucleotide in a DNA or RNA strand. The bases in DNA or RNA are attached to the sugars of the backbone.

mutation

A change in the base sequence of DNA in a gene; often used to refer to a genetic change that is significant enough to alter the appearance or function of the organism.

deoxyribonucleic acid (DNA)

A molecule composed of deoxyribose nucleotides; contains the genetic information of all living cells.

nucleotide substitution

A mutation in which a single base pair in DNA has been changed.

point mutation

A mutation in which a single base pair in DNA has been changed.

insertion mutation

A mutation in which one or more pairs of nucleotides are inserted into a gene.

deletion mutation

A mutation in which one or more pairs of nucleotides are removed from a gene.

inversion

A mutation that occurs when a piece of DNA is cut out of a chromosome, turned around, and reinserted into the gap.

translocation

A mutation that occurs when a piece of DNA is removed from one chromosome and attached to another chromosome.

adenine (A)

A nitrogenous base found in both DNA and RNA; abbreviated as A

cytosine (C)

A nitrogenous base found in both DNA and RNA; abbreviated as C.

guanine (G)

A nitrogenous base found in both DNA and RNA; abbreviated at G.

thymine (T)

A nitrogenous base found only in DNA; abbreviated as T.

free nucleotide

A nucleotide that has not been joined with other nucleotides to form a DNA or RNA strand.

strand

A single polymer of nucleotides; DNA is composed of two strands wound about each other in a double helix; RNA is usually single stranded.

nucleotide

A subunit of which nucleic acids are composed; a phosphate group bonded to a sugar (deoxyribose in DNA), which is in turn bonded to a nitrogen-containing base (adenine, guanine, cytosine, or thymine in DNA). Nucleotides are linked together, forming a strand of nucleic acid, by bonds between the phosphate of one nucleotide and the sugar of the next nucleotide.

bacteriophage

A virus that specifically infects bacteria.

complementary base pair

In nucleic acids, bases that pair by hydrogen bonding. In DNA, adenine is complementary to thymine, and guanine is complementary to cytosine; in RNA, adenine is complementary to uracil, and guanine to cytosine.

semiconservative repication

The process of replication of the DNA double helix; the two DNA strands separate, and each is used as a template for the synthesis of a complementary DNA strand. Consequently, each daughter double helix consists of one parental strand and one new strand.

double helix

The shape of the two-stranded DNA molecule; similar to a ladder twisted lengthwise into a corkscrew shape.