The initial effect of ionizing radiation on a cell is that it causes

• The formation of highly reactive ions.

• Base substitutions.

• DNA to break.

• Bonding between adjacent thymines.

• The cells to get hot.

Which of the following is NOT a product of transcription?

• tRNA

• None of these

• mRNA

• A new strand of DNA

• RNA

An enzyme that copies DNA to make a molecule of RNA is

• RNA polymerase.

• Transposase.

• DNA polymerase.

• Restriction enzyme.

• DNA ligase.

Transformation is the transfer of DNA from a donor to a recipient cell

• As naked DNA in solution.

• By cell-to-cell contact.

• By sexual reproduction.

• By a bacteriophage.

• By crossing over.

The mechanism by which the presence of arabinose controls the arabinose operon is

• Repression.

• Translation.

• Induction.

• Catabolite repression.

• DNA polymerase.

The damage caused by ultraviolet radiation is

• Repaired during transcription.

• Never repaired.

• Repaired by DNA replication.

• Repaired during translation.

• Cut out and replaced.

DNA is constructed of

• None of these.

• A single strand of nucleotides with internal hydrogen bonding.

• Two strands of identical nucleotides with hydrogen bonds between them.

• Two strands of nucleotides running antiparallel.

• Nucleotides bonded A-C and G-T.

Conjugation differs from reproduction because conjugation

• Transfers DNA horizontally, to cells in the same generation.

• Copies RNA to make DNA.

• Replicates DNA.

• Transfers DNA vertically, to new cells.

• Transcribes DNA to RNA.

Repair of damaged DNA might be viewed as a race between an endonuclease and

• Methylase.

• Helicase.

• DNA ligase.

• Primase.

• DNA polymerase.

The cancer gene ras produces mRNA containing an extra exon that includes a number of UAA codons. Cancer cells produce ras mRNA missing this exon. This mistake most likely is due to a mistake by

• DNA polymerase.

• snRNPs.

• A chemical mutagen.

• Photolyases.

• UV radiation.