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63 Cards in this Set

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  • Back

What convinced Hershey and Chase that DNA, rather than protein, is the genetic material of phage T2

Radioactively labeled phage DNA, but not labeled protein, entered the host cell during infection and directed the synthesis of new viruses

Compare and contrast DNA and RNA polynucleotides

Both are polymers of nucleotides consisting of a sugar, a nitrogenous base, and a phosphate. In RNA, the sugar is ribose, in DNA, its deoxyribose. Both RNA and DNA have the bases A,G, and C, but DNA has a T and RNA has a U.

Along one strand of a double helix is the nucleotide sequence GGCATAGGT. What is the complementary sequence for the other DNA strand?


How does complementary base pairing make possible the replication of DNA?

When the two strands of the double helix separate, free nucleotides can base-pair along each strand, leading to the synthesis of new complementary strands.

What is the function of DNA polymerase in DNA replication?

As free nucleotides base-pair to a parental DNA strand, the enzyme covalently bonds them to the 3' end of a growing daughter strand.

What are the functions of transcription and translation?

Transcription is the transfer of information from DNA to RNA. Translation is the use of the information in RNA to make a polypeptide.

What is the minimum number of nucleotides necessary to code for 100 amino acids?

300. (triplets so 100 x 3)

Translate the RNA sequence CCAUUUACG into the corresponding amino acid sequence

Translate the RNA sequence CCAUUUACG into the corresponding amino acid sequence

Pro - Phe - Thr

How does RNA polymerase recognize the start and end of the gene?

Special DNA sequences mark the start (promoter) and end (terminator) of a gene.

Explain why most eukaryotic genes are longer than the mRNA that leaves the nucleus

These genes have introns, noncoding sequences of nucleotides that are spliced out of the initial RNA transcript to produce mRNA.

What is an anticodon, and what is its function

It is the base triplet of a tRNA molecule that couples the tRNA to a complementary codon in the mRNA. This is a key step in translating mRNA to polypeptide.

How does a ribosome facilitate protein synthesis?

A ribosome holds mRNA and tRNA together and connects amino acids from the tRNAs to the growing polypeptide chain.

What would happen if a genetic mutation in a gene changed a start codon to some other codon?

The messenger RNA transcribed from the mutated gene would be nonfunctional because ribosomes could not initiate translation correctly.

What would happen if a codon in the middle of an mRNA mutated from UUA to UAA?

Translation would stop prematurely, because a stop codon was introduced.

Which of the following molecules or structures does not participate directly in translation: ribosomes, transfer RNA, messenger RNA, DNA?

DNA (its really mRNA that is getting the info from DNA)

How could a single nucleotide substitution result in a shortened protein product?

A substitution that changed an amino acid codon into a stop codon would produce a prematurely terminated polypeptide.

Describe one way a virus can perpetuate its genes without destroying the host cell. What is this type of replication cycle called?

Some viruses can insert their DNA into a chromosome of the host cell, which replicates the viral genes when it replicates its own DNA prior to cell division. This is called the lysogenic cycle.

Explain how some viruses replicate without having DNA

The genetic material of these viruses is RNA, which is replicated inside the host cell by special enzymes encoded by the virus. The viral genome (or its complement) serves as mRNA for the synthesis of viral proteins.

Why doesn't a flu shot one year gives us immunity to flu in subsequent years?

Influenza viruses evolve rapidly by frequent mutation; thus, the strains that infect us later will most likely be different from the ones to which we've been vaccinated.

Why is HIV reverse transcriptase a good target for anti-AIDs drug therapy?

Reverse transcriptase is unique to HIV; we do not normally copy genetic information from RNA to DNA, so disabling reverse transcription would not affect a human.

What makes prions different from all other known infectious agents?

Prions are proteins and have no nucleic acid.

The three modes of gene transfer between bacteria are ______________, which is transfer via a virus, __________, which is the uptake of DNA from the surrounding environment; and __________, which is bacterial "mating"

transduction, transformation, conjugation

Plasmids are useful tools for genetic engineering. Can you guess why?

Scientists can take advantage of the ability of plasmids to carry foreign genes to replicate, and to be inherited by progeny cells.

Define nucleotide

A building block of nucleic acids, consisting of a five carbon sugar covalently bonded to a nitrogenous base and one ore more phophate groups.

Define molecular biology

The study of biological structures functions and heredity at the molecular level.

Define messenger RNA (mRNA)

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.

Define P site and A site on ribosomes

P Site - One of two of a ribosomes binding sites for tRNA during translation. The P site holds the tRNA carrying the growing polypeptide chain (P stands for peptidyl tRNA)

A site - one of two of ribosomes binding sites for tRNA during translation. The A site holds the tRNA that carries the next amino acid in the polypetid chain (A stands for aminoactyl tRNA)

Define anticodon

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

Define frameshift mutation

A change in the genetic material that involves the insertion or deletion of one ore more nucleotides in a gene, resulting in a change in the triplet grouping of nucleotides.

Define silent mutation

A mutation in a gene that changes a codon to one that codes for the same amino acid as the original codon.

Define polynucleotide

A polymer made up of many nucleotide monomers covalently bonded together

Define transfer RNA (tRNA)

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

Contrast lytic cycle vs lysogenic cycle

Lytic cycle - A type of viral replication cycle resulting in the release of new viruses by lysis of the host cell

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

Define f factor

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 stands for fertility.

Define ribosomal RNA (rRNA)

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

Define transformation

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

Define reverse transcription

An enzyme encoded and used by retroviruses that catalyzes the synthesis of DNA on an RNA template

Define transduction

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

Define transcription

The synthesis of RNA on a DNA tempalte

Define viroid

A plant pathogen composed of molecules of naked, circulur RNA several hundred nucleotides long

Define capsid

The protein shell that encloses a viral genome

Define conjugation

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

Define prion

An infectious form of protein that may multiply by converting related proteins to more prions. Prions cause several related diseases in different animals, including scrapie in sheep and mad cow disease

Define bacteriophage or phage

A virus that infects bacteria

Define plasmid

A small ring of independently replicating DNA separate from the main chromosomes. Plasmids are found in prokaryotes and yeasts

What are the 3 stop codons?


What is the start codon


Define translation

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

Define sugar phosphate backbone

IN a polynucleotide (DNA or RNA) the altnerating chain of sugar and phosphate to which nitrogenous bases are attached.

Define retrovirus

An RNA virus that reproduces by means of a DNA molecule. IT reverse-transcribes 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

Define prophage

Phage DNA that has inserted by genetic recombination into the DNA of a bacterial chromosome

Define terminator

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.

Define DNA polymerase

A large molecular complex that assembles DNA nucleotides into polynucleotides using a preexisting strand of DNA as a tempalte

Define DNA ligase

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

Define RNA polymerase

A large molecular complex that links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a tempalte

Define R plasmid

A bacterial plasmid that carries genes for enzymes that destroy particular antibiotics, thus making the bacterium resistant to the antibiotics

Define the semiconservative model

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

Define virus

A microscopic particle capable of infecting cells of living organisms and inserting its genetic material. Viruses are generally not considered to be alive because they do not display all the characteristics associated with life.

Define nonsense mutation

A change in the nucleotide sequence of a gene that converts an amino-acid encoding codon to a STOP codon. A nonsense mutation results in a shorted polypeptide

Define missense mutation

A change in the nucleotide sequence of a gene that alters the amino acid sequence of the resulting poplypetid. In a missesnse mutation, a codon is changed from encoding one amino acid to encoding a different amino acid.

Define codon

A 3 nucleotide sequence in mRNA that specifies a particular amino acid or polypeptide termination signal; the basic unit of the genetic code.

Define genetic code

The set of rules that dictates the amino acid translation of each mRNA nucleotide triplet

Define mutation

A change in the genetic information of a cell; the ultimate source of genetic diversity. A mutation also can occur in the DNA or RNA of a virus.