Chapter 10 -- Biology

Front 1

molecular biology

Back 1

The study of the molecular basis of genes and gene expression; molecular genetics.

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bacteriophage

Back 2

A virus that infects bacteria; also called a phage.

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nucleotide

Back 3

An organic monomer consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group. Nucleotides are the building blocks of nucleic acids.

Front 4

polynucleotide

Back 4

A polymer made up of many nucleotides covalently bonded together.

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sugar-phosphate backbone

Back 5

The alternating chain of sugar and phosphate to which the DNA and RNA nitrogenous bases are attached.

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thymine (T)

Back 6

A single-ring nitrogenous base found in DNA

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cytosine (C)

Back 7

A single-ring nitrogenous base found in DNA

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adenine (A)

Back 8

A double-ring nitrogenous base found in DNA and RNA

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guanine (G)

Back 9

A double-ring nitrogenous base found in DNA and RNA

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double helix

Back 10

The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.

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semiconservative model

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

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DNA polymerase

Back 12

An enzyme that assembles DNA nucleotides into polynucleotides using a preexisting strand of DNA as a template.

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DNA ligase

Back 13

An enzyme, essential for DNA replication, that catalyzes the covalent bonding of adjacent DNA nucleotides; used in genetic engineering to paste a specific piece of DNA containing a gene of interest into a bacterial pasmid or other vector.

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transcription

Back 14

The synthesis of RNA on a DNA template

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translation

Back 15

The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of "language" from nucleotides to amino acids.

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triplet code

Back 16

A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.

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codon

Back 17

A three-nucleotide sequence in mRNA that specifies a particular amino acid or polypeptide termination signal; the basic unit of the genetic code.

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genetic code

Back 18

The set of rules giving the correspondence between nucleotide triplets (codons) in mRNA and amino acids in protein.

Front 19

RNA polymerase

Back 19

An enzyme that links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a template.

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promoter

Back 20

A specific nucleotide sequence in DNA, located at the start of a gene, that is the binding site for RNA polyerase and the place where transcription begins.

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terminator

Back 21

A special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, and then to depart from the gene.

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messenger RNA (mRNA)

Back 22

The type of ribonucleic acid that encodes genetic information from dNA and conveys it to ribosomes, where the information is translated into amino acid sequences.

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intron

Back 23

In eukaryotes, a nonexpressed (noncoding) portion of a gene that is excised from the RNA transcript.

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exon

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In eukaryotes, a coding portion of the gene.

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RNA splicing

Back 25

The removal of introns and joining of exons in eukaryotic RNA, forming an mRNA molecule with a continuoues coding sequence; occurs before mRNA leaves the nucleus.

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transfer RNA (tRNA)

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A type of ribonucleic acid that functions as an interpreter in translation. Each tRNA molecule has a specific anticodon, picks up a specific amino acid, and conveys the amino acid to the appropriate codon on mRNA.

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anticodon

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On a tRNA molecule, a specific sequence of three nucleotides that is complementary to a codon triplet on mRNA.

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ribosomal RNA (rRNA)

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The type of ribonucleic acid that, together with proteins, makes up ribosomes; the most abundant type of RNA.

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P site

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One of two of a ribosome's binding sites for tRNA during translation. The P site holds the tRNA carrying the growing polypeptide chain. (P strands for peptidyl tRNA.)

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peptide bond

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The covalent linkage between two amino acid units in a polypeptide; formed by a dehydration reaction.

Front 31

translocation

Back 31

(1) During protein synthesis, the movement of a tRNA molecule carrying a growing polypeptide chain from the A site to the P site on a ribosome.(The mRNA travels with it.) (2) A change in a chromosome resulting from a chromosomal fragment attaching to a nonhomologous chromosome; can occur as a result of an error in meiosis or from mutagenesis.

Front 32

stop codon

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In mRNA, one of three triplets (UAG, UAA, UGA) that signal gene translation to stop.

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mutation

Back 33

A change in the nucleotide sequence of DNA; the ultimate source of genetic diversity.

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reading frame

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The way in which a cell's mRNA-translating machinery groups the mRNA nucleotides into codons.

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mutagenesis

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The creation of mutation

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mutagen

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A chemical or physical agent that interacts with DNA and causes a mutation.

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capsid

Back 37

The protein shell that encloses a viral genome. It may be rodshaped, polyhedral, or more complex in shape.

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lytic cycle

Back 38

A type of viral replication cycle resulting in the relase of new viruses by lysis (breaking open) of the host cell.

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lysogenic cycle

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A type of bacteriophage replication cycle in which the viral genome is incorporated into the bacterial host chromosome as a prophage. New phages are not produced, and the host cell is not killed or lysed unles the viral genome leaves the host chromosome.

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prophage

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Phage DNA that has inseted by genetic recombination into the DNA of a prokaryotic chromosome.

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emerging virus

Back 41

A virus that has appeared suddenly or has recently come to the attention of medical scientists.

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reverse transcriptase

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An enzyme that catalyzes the synthesis of DNA on an RNA template.

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retrovirus

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An RNA virus that reproduces by means of a DNA molecule. It reverse0transcribes its RNA into DNA, inserts the DNA into a cellular chromosome, and then transcribes more copies of the RNA from the viral DNA. HIV and a number of cancer-causing viruses are retroviruses.

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AIDS (Acquired Immune Deficiency Syndrome)

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The late stages of HIV infection, characterized by a reduced number of T cells and the appearance of characteristic secondary infections.

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HIV (Human Immunodeficiency Virus)

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The retrovirus that attacks the human immune system and causes AIDS.

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transformation

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The incorporation of new genes into a cell from DNA that the cell takes up from the surrounding environment.

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transduction

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The transfer of bacterial genes from one bacterial cell to another by a phage.

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conjugation

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The union (mating) of two bacterial cells or protist cells and the transfer of DNA between the two cells.

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F factor

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A piece of DNA that can exist as a bacterial plasmid. The F factor carries genes for making sex pili and other structures needed for conjugation, as well as a site where DNA replication can start. F strands for fertility.

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plasmid

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A small ring of DNA sparate from the chromosome(s). Plasmids are found in prokaryotes and yeast.

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R plasmid

Back 51

A bacterial plasmid that carries genes for enzymes that destory particular antibiotics, thus making th ebacterium resistant to the antibiotics.