6.1 DNA Structure, Replication, and Biotechnology

DNA

A nucleic acid molecule, usually a double-stranded helix, in which each polynucleotide strand consists of nucleotide monomers with a deoxyribose sugar and nitrogenous bases

RNA

A type of nucleic acid consisting of a polynucleotide made up of nucleotide monomers with a ribose sugar and the nitrogenous bases usually single-stranded; functions in protein synthesis, gene regulation, and as the genome of some viruses.; capable of being replicated and determining the inherited structure of a cell’s proteins

Chromosome

A cellular structure consisting of one DNA molecule and associated protein molecule

Nucleoid

A non-membrane-enclosed region in a prokaryotic cell where its chromosome is located

Plasmid

A small, circular, double-stranded DNA molecule that carries accessory genes separate from those of a bacterial chromosome

Double Helix

The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape

Nucleotide

The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one to three phosphate groups

DNA replication

The process by which a DNA molecule is copied; also called DNA synthesis

Semi-conservative replication

Type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and one newly made strand

Replication Fork

Type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and one newly made strand

Template Strand (Parental strand)

The DNA strand that provides the pattern, or template, for ordering, by complementary base pairing, the sequence of nucleotides in an RNA transcript

Complementary Strand (Daughter strand)

A double-stranded DNA molecule made in vitro using mRNA as a template and the enzymes reverse transcriptase and DNA polymerase

Helicase

An enzyme that untwists the double helix of DNA at replication forks, separating the two strands and making them available as template strands

Topoisomerase

A protein that breaks, swivels, and rejoins DNA strands. During DNA replication, topoisomerase helps to relieve strain in the double helix ahead of the replication fork

DNA ligase

A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3′ end of one DNA fragment (such as an Okazaki fragment) to the 5′ end of another DNA fragment (such as a growing DNA chain)

Single-strand binding proteins

A protein that binds to the unpaired DNA strands during DNA replication, stabilizing them and holding them apart while they serve as templates for the synthesis of complementary strands of DNA

Primase

An enzyme that joins RNA nucleotides to make a primer during DNA replication, using the parental DNA strand as a template

Leading Strand

The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5' to 3' direction

Lagging Strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork

Okazaki Fragment

A short segment of DNA synthesized away from the replication fork on a template strand during DNA replication. Many such segments are joined together to make up the lagging strand of newly synthesized DNA

Antiparallel

Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix (they run in opposite 5' to 3' directions)

Nitrogenous Base

DNA: ACTG

RNA: ACUG

Polymerase Chain Reaction

A technique for amplifying DNA in vitro by incubating it with specific primers, a heat-resistant DNA polymerase, and nucleotides

Amplification

The strengthening of stimulus energy during transduction

Primers

A short polynucleotide with a free 3′ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication

Denaturation

the separation of the two strands of the double helix. Denaturation occurs under extreme (noncellular) conditions of pH, salt concentration, or temperature

Annealing

synthetic nucleotide primers bond to the start sequences

Extension

DNA Polymerase synthesizes target DNA

Recombinant DNA

A DNA molecule made in vitro with segments from different sources

Plasmid/vector

An organism that transmits pathogens from one host to another

Restriction enzyme (endonuclease)

An endonuclease (type of enzyme) that recognizes and cuts DNA molecules foreign to a bacterium

Ligase

A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3′ end of one DNA fragment (such as an Okazaki fragment) to the 5′ end of another DNA fragment (such as a growing DNA chain)

Gel Electrophoresis

A technique for separating nucleic acids or proteins on the basis of their size and electrical charge, both of which affect their rate of movement through an electric field in a gel made of agarose or another polymer

Transformation

A change in genotype and phenotype due to the assimilation of external DNA by a cell

Cloning

The production of multiple copies of a specific DNA segment

DNA Sequencing

Determining the order of nucleotide bases in a gene or DNA fragment

Describe the structure of DNA

pentose sugar, phosphate, and a nitrogenous base

Compare the structure of DNA between prokaryotes and eukaryotes

prokaryotic DNA: typically circular and located freely in the cytoplasm, eukaryotic DNA: linear and contained within a membrane-bound nucleus

What is the function of plasmid DNA in prokaryotes?

helps bacteria adapt and survive by carrying genes that provide beneficial traits

What is the chemistry that allows from complementary base pairing

hydrogen bonds forming between specific nitrogenous bases

What is the usefulness of DNA as hereditary material?

it can store and accurately replicate genetic information

What is the genetic composition of clones

genetically identical to the parent cell